Oracle® Fusion Middleware

Administering HTTP Session Management with Oracle Coherence*Web

12c (12.2.1.2.0)

E77769-01

September 2016

Documentation for developers and administrators that describes how to configure, deploy, and use Coherence*Web to managing session state on a variety of applications servers including WebLogic Server.

Oracle Fusion Middleware Administering HTTP Session Management with Oracle Coherence*Web, 12c (12.2.1.2.0)

E77769-01

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Contents

Preface

- Audience

- Documentation Accessibility

- Related Documents

- Conventions

What's New in This Guide

- New and Changed Features

- Other Significant Changes in this Document

1 Introduction to Coherence*Web

- 1.1 Understanding Coherence*Web

- 1.2 Supported Web Containers

- 1.3 Configuration and Deployment Road Map

- 1.3.1 Choose Your Cluster Node Isolation

- 1.3.2 Choose Your Locking Mode

- 1.3.3 Choose How to Scope Sessions and Session Attributes

- 1.3.4 Choose When to Clean Up Expired HTTP Sessions

- 1.3.5 Choose the Integration Method

2 Using Coherence*Web with WebLogic Server

- 2.1 Overview of Coherence*Web

- 2.2 Overview of Managed Coherence Servers

- 2.3 Configuring and Deploying Coherence*Web: Main Steps

- 2.3.1 Installing WebLogic Server and Oracle Coherence

- 2.3.2 Configure Coherence*Web

- 2.3.3 Configure the Session Cookies

- 2.3.4 Start a Cache Server

- 2.3.4.1 Starting a Coherence Cache Server from WebLogic Server Administration Console

- 2.3.4.2 Starting a Coherence Cache Server from the Command Line

- 2.3.4.2.1 To Start a Standalone Coherence Cache Server

- 2.3.4.2.2 To Start a Storage-Enabled or -Disabled WebLogic Server Instance

- 2.3.5 Configure Coherence*Web Storage Mode

- 2.3.6 Deploying Applications to WebLogic Server

- 2.4 Coherence MBean Attributes for Coherence*Web

- 2.4.1 Enabling the Coherence Session Cache in Weblogic Server Administration Console

- 2.5 Using a Custom Session Cache Configuration File

- 2.6 Scoping the Session Cookie Path

- 2.7 Updating the Session ID

- 2.8 Sharing Coherence*Web Sessions with Other Application Servers

3 Using Coherence*Web on Other Application Servers

- 3.1 Integrating Coherence*Web Using the WebInstaller

- 3.1.1 General Instructions for Integrating Coherence*Web Session Management Module

- 3.1.1.1 Deploying and Running Applications In Process

- 3.1.1.2 Deploying and Running Applications Out-of-Process

- 3.1.1.3 Migrating to Out-of-Process Topology

- 3.1.1.4 Deploying and Running Applications Out-of-Process with Coherence*Extend

- 3.1.2 Enabling Sticky Sessions for Apache Tomcat Servers

- 3.1.3 Integrating with IBM WebSphere Liberty

- 3.2 Coherence*Web WebInstaller Ant Task

- 3.2.1 Using the Coherence*Web WebInstaller Ant Task

- 3.2.2 Configuring the WebInstaller Ant Task

- 3.2.3 WebInstaller Ant Task Examples

- 3.3 Testing HTTP Session Management

- 3.4 How the Coherence*Web WebInstaller Instruments a Java EE Application

- 3.5 Integrating Coherence*Web with Applications Using Java EE Security

- 3.6 Preventing Cross-Site Scripting Attacks

4 Coherence*Web Session Management Features

- 4.1 Session Models

- 4.1.1 Monolithic Model

- 4.1.2 Traditional Model

- 4.1.3 Split Model

- 4.1.4 Session Model Recommendations

- 4.1.5 Configuring a Session Model

- 4.1.6 Sharing Data in a Clustered Environment

- 4.1.7 Scalability and Performance

- 4.2 Session and Session Attribute Scoping

- 4.2.1 Session Scoping

- 4.2.1.1 Preventing Web Applications from Sharing Session Data

- 4.2.1.2 Working with Multiple Cache Configurations

- 4.2.1.3 Keeping Session Cookies Separate

- 4.2.2 Session Attribute Scoping

- 4.2.2.1 Sharing Session Information Between Multiple Applications

- 4.3 Cluster Node Isolation

- 4.3.1 Application Server-Scoped Cluster Nodes

- 4.3.2 EAR-Scoped Cluster Nodes

- 4.3.3 WAR-Scoped Cluster Nodes

- 4.4 Session Locking Modes

- 4.4.1 Optimistic Locking

- 4.4.2 Last-Write-Wins Locking

- 4.4.3 Member Locking

- 4.4.4 Application Locking

- 4.4.5 Thread Locking

- 4.4.6 Troubleshooting Locking in HTTP Sessions

- 4.4.7 Enabling Sticky Session Optimizations

- 4.5 Deployment Topologies

- 4.5.1 In-Process Topology

- 4.5.2 Out-of-Process Topology

- 4.5.2.1 Migrating from In-Process to Out-of-Process Topology

- 4.5.3 Out-of-Process with Coherence*Extend Topology

- 4.5.4 Configuring Coherence*Web with Coherence*Extend

- 4.5.4.1 Configure the Cache for Proxy and Storage JVMs

- 4.5.4.2 Configure the Cache for Web Tier JVMs

- 4.6 Accessing Sessions with Lazy Acquisition

- 4.7 Overriding the Distribution of HTTP Sessions and Attributes

- 4.7.1 Implementing a Session Distribution Controller

- 4.7.2 Registering a Session Distribution Controller Implementation

- 4.8 Detecting Changed Attribute Values

- 4.9 Saving Non-Serializable Attributes Locally

- 4.10 Securing Coherence*Web Deployments

- 4.11 Customizing the Name of the Session Cache Configuration File

- 4.12 Configuring Logging for Coherence*Web

- 4.13 Getting Concurrent Access to the Same Session Instance

- 4.14 Federated Session Caches

5 Monitoring Applications

- 5.1 Managing and Monitoring Applications with JMX

- 5.1.1 Managing and Monitoring Applications on WebLogic Server

- 5.2 Running Performance Reports

- 5.2.1 Web Session Storage Report

- 5.2.2 Web Session Overflow Report

- 5.2.3 Web Report

- 5.2.4 WebLogic Web Report

- 5.2.5 Web Service Report

6 Cleaning Up Expired HTTP Sessions

- 6.1 Understanding the Session Reaper

- 6.2 Tuning the Session Reaper

- 6.3 Getting Session Reaper Performance Statistics

- 6.4 Understanding Session Invalidation Exceptions for the Session Reaper

7 Working with JSF and MyFaces Applications

- 7.1 Configuring for all JSF and MyFaces Web Applications:

- 7.2 Configuring for Instrumented Applications that use MyFaces

- 7.3 Configuring for Instrumented Applications that use Mojarra

A Coherence*Web Context Parameters

B Capacity Planning

C Session Cache Configuration File

D Oracle Coherence*Web Extension for OVAB

- D.1 Versions Supported

- D.2 Coherence*Web Introspection Parameters

- D.3 Reference System Prerequisites

- D.4 Requirements

- D.4.1 Deployment Model Requirement

- D.4.2 Requirement to Manually Update Custom Cluster Configuration Files

- D.5 Resulting Artifact Type

- D.6 Wiring

- D.7 Wiring Properties

- D.8 Coherence*Web Appliance Properties

- D.9 Supported Template Types

Preface

This guide describes how to deploy Oracle Coherence*Web (Coherence*Web), an HTTP session management module to WebLogic Server and other application servers. It also describes the different session management features that you can configure.

Audience

This guide is intended for application developers who want to be able to manage session state in clustered environments.

Documentation Accessibility

For information about Oracle's commitment to accessibility, visit the Oracle Accessibility Program website at http://www.oracle.com/pls/topic/lookup?ctx=acc&id=docacc.

Access to Oracle Support

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Related Documents

For more information, see the following in the Oracle Coherence documentation set:

- Administering Oracle Coherence

- Developing Applications with Oracle Coherence

- Developing Remote Clients for Oracle Coherence

- Installing Oracle Coherence

- Integrating Oracle Coherence

- Managing Oracle Coherence

- Securing Oracle Coherence

- Java API Reference for Oracle Coherence

- .NET API Reference for Oracle Coherence

- C++ API Reference for Oracle Coherence

- Release Notes for Oracle Coherence

Conventions

The following text conventions are used in this guide:

Convention

Meaning

boldface

Boldface type indicates graphical user interface elements associated with an action, or terms defined in text or the glossary.

italic

Italic type indicates book titles, emphasis, or placeholder variables for which you supply particular values.

monospace

Monospace type indicates commands within a paragraph, URLs, code in examples, text that appears on the screen, or text that you enter.

What's New in This Guide

The following topics introduce the new and changed features of Oracle Coherence and other significant changes that are described in this guide, and provides pointers to additional information.

New and Changed Features

New and Changed Features for 12c (12.2.1.2)

Oracle Coherence 12c (12.2.1.2) does not contain any new and changed features for this document.

New and Changed Features for 12c (12.2.1.1)

Oracle Coherence 12c (12.2.1.1) includes the following new and changed features for this document.

- Federated caching support in WebLogic Server Console, which simplifies configuration when federating session data across clusters. See "Enabling the Coherence Session Cache in Weblogic Server Administration Console."

New and Changed Features for 12c (12.2.1)

Oracle Coherence 12c (12.2.1) includes the following new and changed features for this document.

- Coherence*Web supports federated caching to replicate cache data asynchronously across multiple geographically dispersed clusters. For details, see "Federated Session Caches."

- Session reaping that is used to invalidate sessions can be configured to use entry processors. For details, see "Understanding How the Session Reaper Removes Sessions."

- Coherence*Web dependencies are included on the WebLogic Server classpath. For details, see "Overview of Coherence*Web."

Other Significant Changes in this Document

Other Significant Changes in This Document for 12c (12.2.1.2)

For 12c (12.2.1.2), this guide has been updated in several ways. Following are the sections that have been added or changed.

- Coherence*Web support on WebLogic Server has been updated. For a complete list of supported web containers, see "Supported Web Containers."

Other Significant Changes in This Document for 12c (12.2.1.1)

For 12c (12.2.1.1), this guide has been updated in several ways. Following are the sections that have been added or changed.

- Coherence*Web supports IBM WebSphere Liberty 8.5.x. No other WebSphere application servers are supported. For a complete list of supported web containers, see "Supported Web Containers."

Other Significant Changes in This Document for 12c (12.2.1.)

For 12c (12.2.1), this guide has been updated in several ways. Following are the sections that have been added or changed.

- Coherence*Web is no longer available for older versions of supported web containers. For a complete list of supported web containers, see "Supported Web Containers."

- The default Coherence*Web cache configuration file (default-session-cache-config.xml) has been updated. To view the current cache definitions, see "Session Cache Configuration File. "

1 Introduction to Coherence*Web

This chapter describes the advantages of using Coherence*Web for managing session state in clustered environments. It lists the containers that can use Coherence*Web and provides a configuration and deployment roadmap. More detailed information on configuration, deployment, and features are provided in following chapters.

This chapter contains the following sections:

- Understanding Coherence*Web

- Supported Web Containers

- Configuration and Deployment Road Map

1.1 Understanding Coherence*Web

Coherence*Web is an HTTP session management module dedicated to managing session state in clustered environments. Built on top of Oracle Coherence (Coherence), Coherence*Web:

- brings Coherence data grid's data scalability, availability, reliability, and performance to in-memory session management and storage.

- can configure fine-grained session and session attribute scoping by way of pluggable policies (see "Session and Session Attribute Scoping").

- can be deployed to many mainstream application servers such as Oracle WebLogic Server, IBM WebSphere, and Tomcat (see "Supported Web Containers").

- allows storage of session data outside of the Java EE application server, freeing application server heap space and enabling server restarts without session data loss (see "Deployment Topologies").

- enables session sharing and management across different Web applications, domains and heterogeneous application servers (see "Session and Session Attribute Scoping").

- can be used in advanced session models (that is, Monolithic, Traditional, and Split Session) that define how the session state is serialized or deserialized in the cluster (see "Session Models").

1.2 Supported Web Containers

For recent releases of WebLogic Server, Coherence*Web is integrated with the product. No installation or special integration steps are necessary. For more information, see Using Coherence*Web with WebLogic Server.

For third-party application servers, Coherence*Web provides a generic utility, the WebInstaller, that transparently instruments your Web applications. Using Coherence*Web on Other Application Servers, describes how to use the WebInstaller to integrate Coherence*Web with these servers.

Table 1-1 summarizes the Web containers supported by the Coherence*Web session management module. It also provides links to the information required to integrate Coherence*Web. Notice that all of the Web containers (except Oracle WebLogic Server) share the same general instructions.

Note:

The value in the Server Type Alias column is used only by the Coherence*Web WebInstaller. The value is passed to the WebInstaller through the -server command-line option.

Table 1-1 Web Containers which can use Coherence*Web

Application Server

Server Type Alias

See this Integration Section

Oracle WebLogic

N/A

Coherence*Web is integrated with WebLogic Server. No integration steps are required. See Using Coherence*Web with WebLogic Server.

Note:

WebLogic Server and Coherence must be on the same versions when using Coherence*Web.

IBM WebSphere Liberty 8.5.n

Liberty/8.5.x

"General Instructions for Integrating Coherence*Web Session Management Module"

Apache Tomcat 7.n

Tomcat/7.x

"General Instructions for Integrating Coherence*Web Session Management Module" and "Enabling Sticky Sessions for Apache Tomcat Servers"

Apache Tomcat 8.n

Tomcat/8.x

"General Instructions for Integrating Coherence*Web Session Management Module" and "Enabling Sticky Sessions for Apache Tomcat Servers"

Jetty 9.3.n

Generic

"General Instructions for Integrating Coherence*Web Session Management Module"

1.3 Configuration and Deployment Road Map

There are deployment decisions you should make before you configure and deploy Coherence*Web. Coherence*Web is supported on many different application servers. Regardless of which application server you are using, you might have to change some Coherence*Web configuration options to meet your particular requirements, such as packaging considerations, session model, session locking mode, and deployment topology.

1.3.1 Choose Your Cluster Node Isolation

Cluster node isolation refers to the scope of the Coherence nodes that are created within each application server JVM. Several different isolation modes are supported.

For example: you might be deploying multiple applications to the container that require the use of the same cluster (or one Coherence node); you might have multiple Web applications packaged in a single EAR file that use a single cluster; or you might have Web applications that must keep their session data separate and must be deployed to their own individual Coherence cluster. These choices and the deployment descriptors and elements that must be configured are described in "Cluster Node Isolation".

1.3.2 Choose Your Locking Mode

Locking mode refers to the behavior of HTTP sessions when they are accessed concurrently by multiple Web container threads. Coherence*Web offers several different session locking options. For example, you can allow multiple nodes in a cluster to access an HTTP session simultaneously, or allow only one thread at a time to access an HTTP session. You can also allow multiple threads to access the same Web application instance while prohibiting concurrent access by threads in different Web application instances. These choices, and the deployment descriptors and elements that must be configured, are described in "Session Locking Modes".

1.3.3 Choose How to Scope Sessions and Session Attributes

Session and session attribute scoping refers to the fine-grained control over how both session data and session attributes are scoped (or shared) across application boundaries. Coherence*Web supports sharing sessions across Web applications and restricts which session attributes are shared across the application boundaries. These choices, and the deployment descriptors and elements that must be configured, are described in "Session and Session Attribute Scoping".

1.3.4 Choose When to Clean Up Expired HTTP Sessions

Coherence*Web provides a session reaper, which invalidates sessions that have expired. Cleaning Up Expired HTTP Sessions, describes the session reaper.

1.3.5 Choose the Integration Method

The integration procedure that you follow depends on your application server. "Supported Web Containers" provides a list of the application servers and the corresponding instructions for integrating Coherence*Web.

If you are using a recent release of WebLogic Server, Coherence and Coherence*Web are installed with the WebLogic Server product. No separate Coherence*Web integration is necessary. See Using Coherence*Web with WebLogic Server.

For other application servers, use the generic Java EE WebInstaller described in Using Coherence*Web on Other Application Servers.

2 Using Coherence*Web with WebLogic Server

This chapter describes how to configure and deploy Coherence*Web, the session state persistence and management module, for use with WebLogic Server. The functionality that allows Coherence*Web to be used with this application server is contained in Coherence*Web.

This chapter also provides an overview of Managed Coherence Servers and the Grid Archive (GAR) format for packaging Coherence applications. A detailed discussion of Managed Coherence Servers and the GAR format is beyond the scope of this document. For more information, see Oracle Fusion Middleware Developing Oracle Coherence Applications for Oracle WebLogic Server.

This chapter contains the following sections:

- Overview of Coherence*Web

- Overview of Managed Coherence Servers

- Configuring and Deploying Coherence*Web: Main Steps

- Coherence MBean Attributes for Coherence*Web

- Scoping the Session Cookie Path

- Updating the Session ID

- Sharing Coherence*Web Sessions with Other Application Servers

2.1 Overview of Coherence*Web

Coherence*Web provides session state persistence and management. It is a session management module that uses Coherence caches for storing and managing session data. Coherence*Web is an alternative to the WebLogic Server in-memory HTTP state replication services. Consider using Coherence*Web if you are encountering any of these situations:

- Your application works with large HTTP session state objects

- You run into memory constraints, due to storing HTTP session object data

- You want to offload HTTP session storage to an existing Coherence cluster

- You want to share session state across enterprise applications and Web modules

The classes that define the Coherence*Web are contained in the coherence-web.jar file. To use the functionality provided by Coherence*Web, the coherence.jar classes must also be available to the Web application. Both of these libraries are on the WebLogic Server system classpath and are automatically loaded at runtime. The coherence-web.jar loads application classes with the appropriate classloader in WebLogic Server.

Note:

WebLogic Server and Coherence must be on the same versions when using Coherence*Web.

Coherence cache configurations and services used by Coherence*Web are defined in the default-session-cache-config.xml file, which can be found in the coherence-web.jar file. The default cache and services configuration defined in the default-session-cache-config.xml file should satisfy most Web applications.

You can create your own custom session cache configuration by packaging a file named session-cache-config.xml in your Web application. For more information see, "Using a Custom Session Cache Configuration File".

When Coherence*Web is started on WebLogic Server, it first looks for a file named session-cache-config.xml. For example, the file can be placed in a WAR file's WEB-INF/classes directory, or packaged in a JAR file and placed in an EAR file's APP-INF/lib directory. If no custom session cache configuration XML resource is found, then it will use the default-session-cache-config.xml file packaged in coherence-web.jar.

In Coherence*Web, the following default cache configurations are defined:

- Coherence*Web for WebLogic Server is configured with local-storage disabled. The server will serve requests and will not be used to host data. This means a Coherence cache server must be running in its own JVM, separate from the JVM running WebLogic Server.

- The timeout for requests to the cache server to respond is 30 seconds. If a request to the cache server has not responded in 30 seconds, a com.tangosol.net.RequestTimeoutException exception is thrown.

All Coherence*Web-enabled applications running on WebLogic Server have application server-scope. In this configuration, all deployed applications become part of one Coherence node. See "Cluster Node Isolation" for more information about cluster node scope.

Coherence*Web provides several session locking modes to control concurrent access of sessions. Both Coherence*Web employs Last Write Wins locking by default. See "Session Locking Modes" for more information about locking modes.

By itself, Coherence*Web does not require a load balancer to run in front of the WebLogic Server tier. However, a load balancer will improve performance. It is required if the same session will be used concurrently and locking is not enabled. The default load balancer enforces HTTP session JVM affinity, however, other load balancing alternatives are available. WebLogic Server ships with several different proxy plug-ins which enforce JVM session stickiness. Documentation for configuring the WebLogic Server proxy plug-in is available at this URL:

http://download.oracle.com/docs/cd/E17904_01/web.1111/e13709/load_balancing.htm

2.2 Overview of Managed Coherence Servers

Oracle WebLogic Server and Coherence have defined Managed Coherence Servers which provide Coherence applications with the same benefits as other Java EE applications that are hosted on WebLogic Server, for example:

- Coherence applications can be deployed in a manner similar to other Java EE applications.

- Coherence applications in the grid can be managed by using WebLogic Server Console and WLST.

- Coherence clusters can be configured by using WebLogic configuration.

- Coherence Grid Archives can be integrated into Enterprise Archives (EAR files).

- Coherence applications can integrate with existing Coherence-based functionality.

Note:

Using multiple Coherence clusters in a single WebLogic Server domain is not recommended.

For more information on Managed Coherence Servers, see "Creating Coherence Applications for WebLogic Server" in Oracle Fusion Middleware Developing Oracle Coherence Applications for Oracle WebLogic Server.

2.3 Configuring and Deploying Coherence*Web: Main Steps

The following steps summarize how to prepare your deployments to use Coherence*Web with applications running on WebLogic Server:

1. Install WebLogic Server and Oracle Coherence. See "Installing WebLogic Server and Oracle Coherence".

2. (Optional) Modify the web.xml file in the deployment if your application requires advanced configuration for Coherence*Web. "Configure Coherence*Web" describes the parameters that can be configured for Web applications. The entire set of Coherence*Web parameters are described in Coherence*Web Context Parameters.

3. (Optional) Configure the WebLogic-generated HTTP session cookie parameters in the weblogic.xml or weblogic-application.xml file. See "Configure the Session Cookies".

4. (Optional for testing; strongly suggested for production) Start a Cache Server Tier in a separate JVM from the one running WebLogic Server. See "Start a Cache Server".

5. Set the Coherence*Web storage mode. See "Configure Coherence*Web Storage Mode".

6. Deploy the application to WebLogic Server. See "Deploying Applications to WebLogic Server".

2.3.1 Installing WebLogic Server and Oracle Coherence

WebLogic Server is installed by executing its installer. The installer provides the full installation and allows you to individually select the components to install (bits, examples, Javadoc, and so on). The installer supports both a graphical mode using the Oracle Universal Installer (OUI) and a silent mode. Installing Coherence is an option in the WebLogic Server installer.

WebLogic Server is always installed to the ORACLE_HOME/wlserver directory; Coherence is always installed to the ORACLE_HOME/coherence directory.

For detailed instructions on installing WebLogic Server and Coherence, see Installing and Configuring Oracle WebLogic Server and Coherence.

2.3.2 Configure Coherence*Web

Coherence*Web provides a default configuration that should satisfy most Web applications. Table 2-1 describes the context parameters configured by Coherence*Web. Table 2-2 describes the compatibility mode context parameter. For complete descriptions of all Coherence*Web parameters, see Coherence*Web Context Parameters.

You can also configure the context parameters on the command line as system properties. The system properties have the same name as the context parameters, but the dash (-) is replaced with a period (.). For example, to declare a value for the context parameter coherence-enable-sessioncontext on the command line, enter it like this:

-Dcoherence.enable.sessioncontext=true

If both a system property and the equivalent context parameter are configured, the value from the system property is used.

Table 2-1 Context Parameters Configured by Coherence*Web

Parameter Name

Description

coherence-application-name

Coherence*Web uses the value of this parameter to determine the name of the application that uses the ApplicationScopeController interface to scope attributes. The value for this parameter should be provided in the following format:

application name + ! + Web module name

The application name is the name of the application that uses the ApplicationScopeController interface and Web module name is the name of the Web module in which it appears.

For example, if you have an EAR file named test.ear and a Web-module named app1 defined in the EAR file, then the default value for the coherence-application-name parameter would be test!app1.

If this parameter is not configured, then Coherence*Web uses the name of the class loader instead. Also, if the parameter is not configured and the ApplicationScopeController interface is configured, then a warning is logged saying that the application name was not configured. See "Session Attribute Scoping" for more information.

coherence-reaperdaemon-assume-locality

This setting allows the session reaper to assume that the sessions that are stored on this node (for example, by a distributed cache service) are the only sessions that this node must check for expiration.

The default is false.

coherence-scopecontroller-class

This value specifies the class name of the optional com.tangosol.coherence.servlet.HttpSessionCollection$AttributeScopeController interface implementation.

Valid values include:

- com.tangosol.coherence.servlet.AbstractHttpSessionCollection$ApplicationScopeController (default)

- com.tangosol.coherence.servlet.AbstractHttpSessionCollection$GlobalScopeController

The default set by Coherence*Web is com.tangosol.coherence.servlet.AbstractHttpSessionCollection$ApplicationScopeController.

Table 2-2 describes the coherence-session-weblogic-compatibility-mode context parameter which is specifically provided by Coherence*Web.

Table 2-2 Context Parameter Provided by the Coherence*Web

Parameter Name

Description

coherence-session-weblogic-compatibility-mode

This parameter is provided by Coherence*Web. If its value is set to true, it determines that a single session ID (with the cookie path set to "/") will map to a unique Coherence*Web session instance in each Web application. If it is false, then the standard behavior will apply: a single session ID will map to a single session instance using Coherence*Web in WebLogic Server. All other session persistence mechanisms in WebLogic use a single session ID in each Web application to refer to different session instances.

This parameter defaults to true unless the global scope controller is specified. If this controller is specified, then the parameter defaults to false.

Table 2-3 describes the coherence-factory-class context parameter. The default value, which is set by Coherence*Web, should not be changed.

Table 2-3 Context Parameter Value that Should Not be Changed

Parameter Name

Description

coherence-factory-class

The fully qualified name of the class that implements the SessionHelper.Factory factory class. Coherence*Web sets the default value to weblogic.servlet.internal.session.WebLogicSPIFactory. This value should not be changed.

2.3.3 Configure the Session Cookies

If you are using Coherence*Web, then WebLogic Server generates and parses the session cookie. In this case, any native Coherence*Web session cookie configuration parameters will be ignored. To configure the session cookies, use the WebLogic-generated HTTP ssion cookie parameters in the weblogic.xml or weblogic-application.xml files. Table 2-4 describes these parameters.

In this table, Updatable? indicates whether the value of the parameter can be changed while the server is running. Not applicable indicates that there is no corresponding Coherence session cookie parameter.

Table 2-4 WebLogic-Generated HTTP Session Cookie Parameters

This Session Cookie Parameter...

Replaces this Coherence*Web Cookie Parameter

Description

cookie-comment

Not applicable

Specifies the comment that identifies the session tracking cookie in the cookie file.

The default is null.

Updatable? Yes

cookie-domain

coherence-session-cookie-domain

Specifies the domain for which the cookie is valid. For example, setting cookie-domain to.mydomain.com returns cookies to any server in the *.mydomain.com domain.

The domain name must have at least two components. Setting a name to *.com or *.net is not valid.

If not set, this attribute defaults to the server that issued the cookie.

For more information, see Cookie.setDomain() in the Servlet specification.

The default is null.

Updatable? Yes

cookie-max-age-secs

coherence-session-max-age

Sets the life span of the session cookie, in seconds, after which it expires on the client. For more information about cookies, see "Using Sessions and Session Persistence" in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server.

The default value is -1 (unlimited).

Updatable? Yes

cookie-name

coherence-session-cookie-name

Defines the session-tracking cookie name. Defaults to JSESSIONID if not set. You can set this to a more specific name for your application.

The default is JSESSIONID.

Updatable? Yes

cookie-path

coherence-session-cookie-path

Defines the session-tracking cookie path.

If not set, this attribute defaults to a slash ("/") where the browser sends cookies to all URLs served by WebLogic Server. You can set the path to a narrower mapping, to limit the request URLs to which the browser sends cookies.

The default is null.

Updatable? Yes

cookie-secure

coherence-session-cookie-secure

Tells the browser that the cookie can be returned only over an HTTPS connection. This ensures that the cookie ID is secure and should be used only on Web sites that use HTTPS. Session cookies sent over HTTP will not work if this feature is enabled.

Disable the url-rewriting-enabled element if you intend to use this feature.

WebLogic Server generates the session cookie.

The default is false.

Updatable? Yes

cookies-enabled

coherence-session-cookies-enabled

Enables use of session cookies by default and is recommended, but you can disable them by setting this property to false. You might turn this option off for testing purposes.

The default is true.

Updatable? Yes

debug-enabled

Not applicable

Enables the debugging feature for HTTP sessions. Support it by enabling HttpSessionDebug logging and the WebLogic Server trace logger.

The default value is false.

Updatable? Yes

encode-session-id-in-query-params

Not applicable

Is set to true if the latest servlet specification requires containers to encode the session ID in path parameters. Certain Web servers do not work well with path parameters. In such cases, the encode-session-id-in-query-params element should be set to true.

WebLogic Server generates the HTTP response.

The default value is false.

Updatable? Yes

http-proxy-caching-of-cookies

Not applicable

When set to false, WebLogic Server adds the following header and response to indicate that the proxy caches are not caching the cookies:“Cache-control: no-cache=set-cookie"

WebLogic Server generates the HTTP response.

The default value is true.

Updatable? Yes

id-length

coherence-session-id-length

Sets the size of the session ID.

The minimum value is 8 bytes and the maximum value is Integer.MAX_VALUE.

If you are writing a Wireless Application Protocol (WAP) application, you must use URL rewriting because the WAP protocol does not support cookies. Also, some WAP devices have a 128-character limit on URL length (including attributes), which limits the amount of data that can be transmitted using URL rewriting. To allow more space for attributes, use this attribute to limit the size of the session ID that is randomly generated by WebLogic Server.

You can also limit the length to a fixed 52 characters, and disallow special characters, by setting the WAPEnabled attribute. For more information, see "URL Rewriting and Wireless Access Protocol" in Developing Web Applications for WebLogic Server.

The default is 52.

Updatable? No

invalidation-interval-secs

Not applicable

Sets the time, in seconds, that Coherence*Web waits between checks for timed-out and invalid sessions, and deleting the old sessions and freeing up memory. Use this element to tune WebLogic Server for best performance on high traffic sites.

The default is 60.

Updatable? No

timeout-secs

Not applicable

Sets the time, in seconds, that Coherence*Web waits before timing out a session.

On busy sites, you can tune your application by adjusting the timeout of sessions. While you want to give a browser client every opportunity to finish a session, you do not want to tie up the server needlessly if the user has left the site or otherwise abandoned the session.

This element can be overridden by the session-timeout element (defined in minutes) in web.xml.

The default is 3600 seconds.

Updatable? No

tracking-enabled

Not applicable

Enables session tracking between HTTP requests.

WebLogic Server generates the HTTP response.

The default is true.

Updatable? No

url-rewriting-enabled

coherence-session-urlencode-enabled

Enables URL rewriting, which encodes the session ID into the URL and provides session tracking if cookies are disabled in the browser and the encodeURL or encodeRedirectedURL methods are used when writing out URLs. For more information, see:

http://www.jguru.com/faq/view.jsp?EID=1045

WebLogic Server generates the HTTP response.

The default is true.

Updatable? Yes

2.3.4 Start a Cache Server

A Coherence cache server is responsible for storing and managing all cached data. Coherence is integrated within WebLogic Server as a container subsystem. The use of a container aligns the lifecycle of a Coherence cluster member with the lifecycle of a managed server: starting or stopping a managed server JVM starts and stops a Coherence cluster member. Managed servers that are cluster members are referred to as managed Coherence servers.

Coherence clusters are different than WebLogic Server clusters. They use different clustering protocols and are configured separately. Multiple WebLogic Server clusters can be associated with a Coherence cluster and a WebLogic Server domain can contain only a single Coherence cluster. Managed servers that are configured as Coherence cluster members are referred to as managed Coherence servers.

Managed Coherence servers can be explicitly associated with a Coherence cluster or they can be associated with a WebLogic Server cluster that is associated with a Coherence cluster. WebLogic Server-managed servers that are members of a Coherence cluster and are storage-enabled, act as cache servers.

For more information on Coherence clusters in a WebLogic server environment, see "Configuring and Managing Coherence Clusters" in Administering Clusters for Oracle WebLogic Server. For more information on Coherence applications in a WebLogic Server environment, see Oracle Fusion Middleware Developing Oracle Coherence Applications for Oracle WebLogic Server.

You can start a Coherence cache server or cluster either from the WebLogic Server Administration Console or from the command line, as described in the following sections.

- Starting a Coherence Cache Server from WebLogic Server Administration Console

- Starting a Coherence Cache Server from the Command Line

2.3.4.1 Starting a Coherence Cache Server from WebLogic Server Administration Console

Using the WebLogic Server Administration Console, you can enable storage for each WebLogic Server that is a member of a Coherence cluster. The Coherence session caches have a separate flag for enabling storage. For more information on this flag, see "Enabling the Coherence Session Cache in Weblogic Server Administration Console".

Note:

If your managed server is a member of a Coherence cluster and is using Coherence*Web, then you can enable session storage by adding the -Dcoherence.session.localstorage=true system property to the startup command.

Coherence session caches automatically start with the WebLogic Server cluster.

The following steps summarize how to start a Coherence cluster in the WebLogic Server Administration Console.

1. Configure the Coherence Cluster.

For detailed information, see "Configuring and Managing Coherence Clusters" in Administering Clusters for Oracle WebLogic Server.

2. Configure WebLogic Servers and clusters that will be associated with the Coherence cluster.

For detailed information, see "Configuring and Managing Coherence Clusters" in Administering Clusters for Oracle WebLogic Server.

3. Enable Coherence*Web for the selected WebLogic Servers or clusters.

For detailed information, see "Enabling the Coherence Session Cache in Weblogic Server Administration Console".

2.3.4.2 Starting a Coherence Cache Server from the Command Line

Instead of using the WebLogic Server Administration Console, there may be situations when you might need to start a Coherence cache server or cluster from the command line. You can start the Coherence cache server from the command line either in standalone mode, or as part of a WebLogic Server instance.

- To Start a Standalone Coherence Cache Server

- To Start a Storage-Enabled or -Disabled WebLogic Server Instance

2.3.4.2.1 To Start a Standalone Coherence Cache Server

Follow these steps to start a standalone Coherence cache server:

1. Create a script for starting a Coherence cache server. The following is a simple example of a script that creates and starts a storage-enabled cache server. This example assumes that you are using a Sun JVM. See "JVM Tuning" in Developing Applications with Oracle Coherence for more information.

java -server -Xms512m -Xmx512m
-cp <Coherence installation dir>/lib/coherence-web.jar:<Coherence installation dir>/lib/coherence.jar -Dcoherence.management.remote=true
-Dcoherence.cacheconfig=session_cache_configuration_file
-Dcoherence.session.localstorage=true -Dcoherence.cluster=Coherence_cluster_name com.tangosol.net.DefaultCacheServer

You must include coherence-web.jar and coherence.jar on the classpath. The variable session_cache_configuration_file represents the absolute path to the cache configuration file on your file system. For Coherence*Web, the default session cache configuration file is named default-session-cache-config.xml. Note that the cache configuration defined for the cache server must match the cache configuration defined for the application servers which run on the same Coherence cluster.

If your application uses additional Coherence caches, then you must merge the cache configuration information with a customized session cache configuration file. This customized session cache configuration file, typically named session-cache-config.xml, should contain the contents of default-session-cache-config.xml file and the additional caches used by your application.

The cache and session configuration must be consistent across WebLogic Server and Coherence cache servers.

For more information on merging these files, see "Merging Coherence Cache and Session Information" in Integrating Oracle Coherence.

The variable Coherence_cluster_name represents the name of the Coherence cluster. A cluster name check has been added to 10.3.6 and later versions of WebLogic Server. The coherence.cluster property must be added to the cache server because you are declaring the cluster name in the WebLogic Server application. If the Coherence servers are started in standalone mode, they must pass this property, otherwise the cluster will not form between the WLS servers and the standalone cache server.

2. Start one or more Coherence cache servers using the script described in the previous step.

2.3.4.2.2 To Start a Storage-Enabled or -Disabled WebLogic Server Instance

By default, a Coherence*Web-enabled WebLogic Server instance starts in storage-disabled mode. To start the WebLogic Server instance in storage-enabled mode, follow these steps:

1. Create a script for starting a Coherence cache server. This can be similar to the script described in the previous section.

2. Include the command-line property to enable local storage, -Dcoherence.session.localstorage=true, in the server startup command. The WebLogic Server instance will start with Coherence*Web-enabled and local storage enabled.

To start a Coherence*Web-enabled WebLogic Server instance, omit this system property. Local storage will be disabled by default.

For more information about working with WebLogic Server through the command line, see "weblogic.Server Command-Line Reference" in Oracle Fusion Middleware Command Reference for Oracle WebLogic Server.

2.3.5 Configure Coherence*Web Storage Mode

You can enable Coherence*Web session storage by specifying coherence-web as the value of the persistent-store-type attribute in the weblogic.xml session configuration. This configuration provides application server-level cluster node scoping for web applications deployed on WebLogic Server. No shared libraries need to be deployed or depended upon.

Coherence*Web is initialized only when a web application that requires session persistence is started in the WebLogic Server instance.

Example 2-1 illustrates a sample weblogic.xml file where coherence-web is the value of the persistent-store-type attribute.

Example 2-1 Coherence Web Storage Mode in weblogic.xml

<weblogic-web-app>
...
<session-descriptor>
<persistent-store-type>coherence-web</persistent-store-type>
</session-descriptor>
...
</weblogic-web-app>

2.3.6 Deploying Applications to WebLogic Server

If you are using the default session cache configuration file with your web application, then you can package and deploy it like any other Java EE application. However, if you are using a custom session cache configuration file, then you must package and deploy the application in a GAR file.

GAR files deploy like any other Java EE application, except that you create a Coherence tier and nodes belonging to the tier. You can configure and deploy a standalone GAR or an embedded GAR.

For information about configuring and deploying standalone GAR files and embedded GAR files, see "Deploying Coherence Applications to WebLogic Server" in Administering Oracle Coherence and "Creating Coherence Applications for WebLogic Server" in Developing Oracle Coherence Applications for Oracle WebLogic Server.

2.4 Coherence MBean Attributes for Coherence*Web

WebLogic Server defines a cluster MBean (weblogic.management.configuration.ClusterMBean) which represents a cluster in the domain. The cluster MBean defines a number of attributes, operations, and MBeans related to the management of the cluster. Among the MBeans defined by the cluster MBean are the CoherenceMemberConfigMBean and the CoherenceTierMBean MBeans.

The CoherenceMemberConfigMBean and the CoherenceTierMBean MBeans each define an isCoherenceWebLocalStorageEnabled attribute that indicates whether a cluster or member is acting as a storage tier for Coherence*Web. This attribute is defined in Table 2-5.

Table 2-5 Coherence MBean Attribute for Coherence*Web

Attribute

Description

isCoherenceWebLocalStorageEnabled

If this attribute is set to true in CoherenceTierMBean, it indicates that a cluster is acting as a storage tier for Coherence*Web. Coherence*Web cache services will start with storage enabled when the server starts. When deploying a Coherence*Web-enabled application, there must be a running WebLogic cluster in the domain which has this attribute enabled.

If this attribute is set to true in CoherenceMemberConfigMBean, it indicates that this node is acting as a storage node for Coherence*Web. Coherence*Web cache services will start with storage enabled when the server starts. When deploying a Coherence*Web-enabled application, there must be a running WebLogic cluster in the domain which has this attribute enabled.

Default: false

2.4.1 Enabling the Coherence Session Cache in Weblogic Server Administration Console

The Coherence Web Local Storage Enabled and Coherence Web Federated Storage Enabled checkboxes in the WebLogic Server Administration Console can be used to indicate whether the cluster is acting as a storage tier for Coherence*Web. When selecting the federated storage option, the default federation topology which is configured is used. For details about configuring federation, see Configuring Cache Federation. For details about using Coherence*Web with federation, see Federated Session Caches.

1. Select Environment, then Clusters in the Domain Structure Window.

2. Select a defined cluster in the Clusters table.

3. Select Configuration tab then the Coherence tab in the Settings for cluster page.

Figure 2-1 illustrates the checkboxes in the WebLogic Server Administration Console.

Figure 2-1 Coherence Web Local Storage Enabled Checkbox

2.5 Using a Custom Session Cache Configuration File

The coherence-web.jar file contains a default-session-cache-config.xml cache configuration file which should be sufficient for most applications. However, if you are working with technologies such as Coherence*Extend or Push Replication, or if you have WebLogic Server nodes that are to act as storage-enabled cache servers with a custom session cache configuration, then you must provide a custom session cache configuration file. Custom session cache configuration files must be packaged in a GAR file for deployment.

To use a custom session cache configuration file on WebLogic Server and package it in a GAR file, follow these steps for web applications and for the WebLogic Server nodes acting as cache servers:

For web applications using Coherence*Web:

1. If you are using a custom session cache configuration file (which should be named session-cache-config.xml), then package it in your web application:

- For a WAR file, place the session cache configuration file in the WEB-INF/classes folder

- For an EAR file, package the session cache configuration file in a JAR file and place it in the shared library (the APP-INF/lib folder) in an EAR file

Note that you can customize the session cache configuration file name, but then you must provide the new file name as the value of the coherence-cache-configuration-path context parameter in the web.xml file.

2. If you do not want the WebLogic Server cluster members running the Coherence*Web application to act as a cache server, then ensure that the Coherence Web Local Storage Enabled checkbox in the WebLogic Server Administration Console "Settings for cluster" page is not selected for the cluster members. This will cause the custom session cache configuration file to be read.

For WebLogic Server nodes acting as cache servers:

1. If you are using a custom session cache configuration file, then construct a GAR file containing the file and a coherence-application.xml file. The GAR file has the following structure:

my.gar
session-cache-config.xml
META-INF
coherence-application.xml
MANIFEST.MF

For more information on the packaging requirements for a GAR file, see "Packaging Coherence Applications for WebLogic Server" in Administering Oracle Coherence and "Creating Coherence Applications for Oracle WebLogic Server" in Developing Oracle Coherence Applications for Oracle WebLogic Server.

a. Create the custom session cache configuration file and name it session-cache-config.xml.
If you are deploying a GAR file, set the local-storage parameter in the custom session-cache-config.xml file to true, to configure all caches to start with storage enabled, for example:

<local-storage>true</local-storage>

Note:

The local-storage parameter specifies whether a cluster node contributes storage to the cluster. In WebLogic Server, the local-storage parameter does not enable storage in Coherence*Web for WebLogic Server members that have a GAR file deployed to them.

b. Create a coherence-application.xml file. In the file, use the cache-configuration-ref parameter to reference your custom session-cache-config.xml file, for example:

<?xml version="1.0"?>
<coherence-application>
xmlns="http://xmlns.oracle.com/weblogic/coherence-application">
<cache-configuration-ref>session-cache-config.xml</cache-configuration-ref>
</coherence-application>

2. Deploy the GAR file to the WebLogic Server cluster that is to act as the storage-enabled Coherence cluster members.
Note that storage must be enabled in either of the following ways:

- Enable storage in the session-cache-config.xml file (see Step 1a).

- Enable storage in the server itself either by selecting the Coherence Web Local Storage Enabled checkbox in the WebLogic Server Administration Console or by setting the JVM argument coherence.session.localstorage to true.

For information on deploying GAR files, see "Deploying Coherence Applications To a WebLogic Server Domain" in Administering Oracle Coherence. and "Deploying Coherence Applications in WebLogic Server" in Developing Oracle Coherence Applications for Oracle WebLogic Server.

2.6 Scoping the Session Cookie Path

WebLogic Server and Coherence*Web handle session scoping and the session lifecycle in different ways. This can impact your decision to implement a single sign-on (SSO) strategy for your applications.

By default, WebLogic Server uses the same session ID in every Web application for a given client, and sets the session cookie path to a forward slash (/). This is a requirement of the WebLogic Server default thin SSO implementation, which is enabled by default. By generating a session cookie with a path of "/", clients always return the same session ID in every request to the server. In WebLogic Server, a single session ID can be mapped to multiple session objects. Each Web application will have a different session object instance even though the session ID is identical (unless session sharing is enabled).

In contrast, Coherence*Web maps a session ID to a single session instance. This means that the behavior of having multiple session instances mapped to the same ID is not replicated by default if an application uses Coherence*Web. Because the session cookie is mapped to "/" by default, a single Coherence*Web session is shared across all Web applications. The default configuration in Coherence*Web is that all session attributes are scoped to a Web application. For most purposes, this single session approach is transparent. The major difference of having a single session across all Web applications is the impact of session invalidation. If Coherence*Web is enabled and you invalidate a session in one Web application, then you invalidate that session in all Web applications that use that session instance. If your Web applications do not use thin SSO, then you can avoid this issue by scoping the session cookie to the Web application path.

Therefore, you have the following options regarding SSO:

- Enable "WebLogic Server session compatibly mode". This configuration is set with the coherence-session-weblogic-compatibility-mode parameter and mirrors all of the native WebLogic Server session persistence types: memory (single-server, non-replicated), file system persistence, JDBC persistence, cookie-based session persistence, and in-memory replication (across a cluster). By default, this mode is enabled. See "Using Sessions and Session Persistence" in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server for more information.

- Enable thin SSO functionality. Clients will use a single session across all Web applications. This means that the session life cycle will be inconsistent with all other session persistence types.

- Disable the thin SSO functionality by scoping the session cookie path to the Web application context path. This will allow the session life cycle to be consistent with all other session persistence types.

One advantage of enabling thin SSO with Coherence*Web is that it will work across all Web applications that are using the same Coherence cluster for Coherence*Web. The Coherence cluster is completely independent from the WebLogic Server cluster. The thin SSO functionality can even span multiple domains by enabling cross-domain trust in the WebLogic Server security layer.

2.7 Updating the Session ID

When a user successfully authenticates a protected resource, the session ID is changed for security purposes.

In previous releases of WebLogic Server, a new session would be created, all of the session attributes from the old session would be copied into the new session, and then the old session would be invalidated. This would trigger the session listeners (if any were registered), so session lifecycle and session attribute listeners would be executed.

The current release of WebLogic Server implements the HttpServletRequest.changeSessionId method from the Java Servlet 3.1 Specification. The implementation of the changeSessionId method allows the actual session ID to be updated. This means that no session lifecycle events will be triggered and no listeners will be executed. Most users should not notice any changes in the behavior of their applications.

For more information on the HttpServletRequest.changeSessionId method, see the Java Servlet 3.1 Specification and Javadoc available from this URL:

http://jcp.org/en/jsr/detail?id=340

2.8 Sharing Coherence*Web Sessions with Other Application Servers

If you are running Coherence*Web on WebLogic Server and on other application servers within a single cluster, then the session cookies created by WebLogic Server will not be decoded correctly by Coherence*Web on the other servers. This is because WebLogic Server adds a session affinity suffix to the cookie which is not part of the session ID stored in Coherence*Web. The other application servers must remove the WebLogic session affinity suffix from the session cookie value for Coherence*Web to be able to retrieve the session from the Coherence cache.

To strip the WebLogic session affinity suffix from the session cookie, add the coherence-session-affinity-token context parameter to the web.xml file used in the other application servers. Set the parameter value to an exclamation point (!), as illustrated in Example 2-2. The session affinity suffix will be removed from the session cookie when it is processed by the other application server.

Example 2-2 Removing Session Affinity Suffix

...
<context-param>
<param-name>coherence-session-affinity-token</param-name>
<param-value>!</param-value>
</context-param>
...

See Coherence*Web Context Parameters for more information on the coherence-session-affinity-token context parameter.

3 Using Coherence*Web on Other Application Servers

This chapter describes how to configure and deploy Coherence*Web, the session state persistence and management module, for use with a variety of application servers. The functionality that allows Coherence*Web to be used with these application servers is provided by running the automated Coherence*Web WebInstaller.

Note:

Consult "Supported Web Containers" to see if you must perform any application server-specific integration steps.

This chapter provides instructions on how to use the Coherence*Web WebInstaller to integrate Coherence*Web with Java EE applications on a variety of different application servers.

This chapter contains the following sections:

- Integrating Coherence*Web Using the WebInstaller

- Coherence*Web WebInstaller Ant Task

- Testing HTTP Session Management

- How the Coherence*Web WebInstaller Instruments a Java EE Application

- Integrating Coherence*Web with Applications Using Java EE Security

- Preventing Cross-Site Scripting Attacks

3.1 Integrating Coherence*Web Using the WebInstaller

Coherence*Web can be enabled for Java EE applications on several different Web containers. To do this, you must run the ready-to-deploy application through the automated Coherence*Web WebInstaller before deploying it. This utility prepares the application for deployment. It performs the integration process in two discrete steps: an inspection step and an integration step. For more information about what the WebInstaller utility does during these steps, see "How the Coherence*Web WebInstaller Instruments a Java EE Application".

WebInstaller can be run either from the Java command line or from Ant tasks. The following sections describe the Java command-line method. For an Ant task-based environment, see "Coherence*Web WebInstaller Ant Task".

3.1.1 General Instructions for Integrating Coherence*Web Session Management Module

Complete the following steps to integrate Coherence*Web with a Java EE application on any of the Web containers listed under "Supported Web Containers".

If you are integrating Coherence*Web with a Java EE application on an Apache Tomcat Server, see also "Enabling Sticky Sessions for Apache Tomcat Servers" for additional instructions.

If you are integrating Coherence*Web with a Java EE application on an IBM WebSphere Server, see also "Integrating with IBM WebSphere Liberty" for additional instructions.

To integrate Coherence*Web for the Java EE application you are deploying:

1. Ensure that the application directory and the EAR file or WAR file are not being used or accessed by another process.

2. Change the current directory to the Coherence library directory (%COHERENCE_HOME%\lib on Windows and $COHERENCE_HOME/lib on UNIX).

3. Ensure that the paths are configured so that Java commands will run.

4. Complete the application inspection step by running the following command. Specify the full path to your application and the name of your server found in Table 1-1 (replacing the <app-path> and <server-type> with them in the following command line):

java -jar webInstaller.jar <app-path> -inspect -server:<server-type>

The system will create (or update, if it already exists) the coherence-web.xml configuration descriptor file for your Java EE application in the directory where the application is located. This configuration descriptor file contains the default Coherence*Web settings for your application as recommended by the utility.

5. If necessary, review and modify the Coherence*Web settings based on your requirements.

You can modify the Coherence*Web settings by editing the coherence-web.xml descriptor file. Coherence*Web Context Parameters, describes the Coherence*Web settings that can be modified. Use the param-name and param-value subelements of the context-param parameter to enable the features you want. Table 3-1 describes some examples of different settings.

Table 3-1 Example Context Parameter Settings for Coherence*Web

Parameter

Name

Description

coherence-servletcontext-clustered

true

Clusters all ServletContext (global) attributes so that servers in a cluster share the same values for those attributes, and also receive the events specified by the Servlet Specification when those attributes change.

Note:

This property is not applicable for IBM WebSphere Liberty.

coherence-enable-sessioncontext

true

Allows an application to enumerate all of the sessions that exist within the application, or to obtain any one of those sessions to examine or manipulate.

coherence-session-id-length

32

Enables you to increase the length of the HttpSession ID, which is generated using a SecureRandom algorithm; the length can be any value, although in practice it should be small enough to fit into a cookie or a URL (depending on how session IDs are maintained.) Increasing the length can decrease the chance of a session being purposely hijacked.

coherence-session-urlencode-enabled

true

By default, the HttpSession ID is managed in a cookie. If the application supports URL encoding, this option enables it.

6. Complete the Coherence*Web application integration step by running the following command, replacing <app-path> with the full path to your application:

java -jar webInstaller.jar <app-path> -install

The WebInstaller requires a valid coherence-web.xml configuration descriptor file to reside in the same directory as the application. The command creates a default-session-cache-config.xml file in the WEB-INF\classes directory of the application archive file. This file contains the session and cache configuration information.

7. Deploy the updated application and verify that everything functions as expected, using the lightweight load balancer provided with the Coherence distribution. Remember that the lightweight load balancer is not a production-ready utility, in contrast to the load balancer provided by WebLogic Server.

The application can be deployed and run in any of the deployment topologies supported by Coherence: in-process, out-of-process, or out-of-process with Coherence*Extend. See the following sections for information on deploying and running your applications under these topologies. For more information on the topologies themselves, see "Deployment Topologies".

3.1.1.1 Deploying and Running Applications In Process

Coherence*Web can be run in-process with the application server. This is where session data is stored with the application server. See "In-Process Topology" for more information on this topology.

For the application server:

1. Start the application server in storage-enabled mode. Add the system property coherence.session.localstorage=true to the Java options of your application server startup script.

2. Deploy the coherence.jar and coherence-web.jar files as shared libraries.

3. Deploy and run your application.

3.1.1.2 Deploying and Running Applications Out-of-Process

In the out-of-process deployment topology, a stand-alone cache server stores the session data and the application server is configured as a cache client. See "Out-of-Process Topology" for more information on this topology.

The cache server and the application server must use the same cache and session configuration. This configuration is generated in the default-session-cache-config.xml file by the Coherence*Web WebInstaller. The WebInstaller generates the file in the WEB-INF\classes directory of the instrumented application.

For the cache server:

1. Add the coherence.cacheconfig system property to the cache server startup script to locate the file configuration file. You must also include the system property coherence.session.localstorage=true to enable storage for the cache server.

2. Add the coherence.jar and coherence-web.jar files to the classpath in the cache server startup script.
Following is a sample startup script:

java -server -Xms512m -Xmx512m
-cp <Coherence installation dir>/lib/coherence.jar:<Coherence installation dir>/lib/coherence-web.jar -Dcoherence.management.remote=true -Dcoherence.cacheconfig=default-session-cache-config.xml
-Dcoherence.session.localstorage=true com.tangosol.net.DefaultCacheServer

For the application server (cache client):

1. Deploy the coherence.jar and coherence-web.jar files as shared libraries.

2. The default-session-cache-config.xml file should already be present in the WEB-INF\classes directory of the instrumented application.

By default, the file should specify that local storage is disabled (if you are not sure, you can either inspect the file to confirm that the local-storage element is set to false or add the system property coherence.session.localstorage=false to the startup script).

3. Deploy the application to the server.

3.1.1.3 Migrating to Out-of-Process Topology

If you have been running and testing your application with Coherence*Web in-process, you can easily migrate to the out-of-process topology. Simply set up your cache server and application server as described in "Deploying and Running Applications Out-of-Process".

3.1.1.4 Deploying and Running Applications Out-of-Process with Coherence*Extend

The out-of-process with Coherence*Extend topology is similar to the out-of-process topology except that the communication between the application server tier and the cache server tier is over Coherence*Extend (TCP/IP). Coherence*Extend consists of two components: an extend client (or proxy) running outside the cluster and an extend proxy service running in the cluster hosted by one or more cache servers. See "Out-of-Process with Coherence*Extend Topology" for more information on this topology.

In these deployments, there are three types of participants:

- Cache servers (storage servers), which are used to store the actual session data in memory.

- Web (application) servers, which are the Extend clients in this topology. They are not members of the cluster; instead, they connect to a proxy node in the cluster that will issue requests to the cluster on their behalf.

- Proxy servers, which are storage-disabled members (nodes) of the cluster that accept and manage TCP/IP connections from Extend clients. Requests that arrive from clients will be sent into the cluster, and responses will be sent back through the TCP/IP connections.

For the cache server:

Follow the instructions for configuring the cache server in "Deploying and Running Applications Out-of-Process". Also, edit the cache server's copy of the default-session-cache-config.xml file to add the system properties coherence.session.proxy=false and coherence.session.localstorage=true.

See "Configure the Cache for Proxy and Storage JVMs" for more information and an example of a default-session-cache-config.xml file with these context parameters.

For the Web tier (application) server:

Follow the instructions for configuring the application server in "Deploying and Running Applications Out-of-Process". Also, complete these steps:

1. Ensure that Coherence*Web is configured to use the Optimistic Locking mode. Optimistic locking is the default locking mechanism for Coherence*Web (see"Optimistic Locking").

2. Edit the application server's copy of the default-session-cache-config.xml file to add the proxy JVM host names, IP addresses and ports. To do this, add a <remote-addresses> section to the file. In most cases, you should include the host name and IP address, and port of all proxy JVMs for load balancing and failover.

See "Configure the Cache for Web Tier JVMs" for more information and an example of a default-session-cache-config.xml file with a <remote-addresses> section.

For the proxy server:

With a few changes, the proxy server can use the same cache and session configuration as the application server and the cache server. Edit the default-session-cache-config.xml file to add these system properties:

- coherence.session.localstorage=false to disable local storage.

- coherence.session.proxy=true to indicate that a proxy service is being used.

- coherence.session.proxy.localhost to indicate the host name or IP address of the NIC to which the proxy will bind.

- coherence.session.proxy.localport to indicate a unique port number to which the proxy will bind.

See "Configure the Cache for Proxy and Storage JVMs" for more information and an example of a default-session-cache-config.xml file with these context parameters.

3.1.2 Enabling Sticky Sessions for Apache Tomcat Servers

If you want to employ sticky sessions for the Apache Tomcat Server, you must configure the jvmRoute attribute in the server's server.xml file. You can find more information on this attribute at this URL:

http://tomcat.apache.org/connectors-doc/reference/workers.html

3.1.3 Integrating with IBM WebSphere Liberty

HTTP session affinity may need to be explicitly configured when integrating with WebSphere Liberty. Coherence*Web needs to be passed the Clone ID of the Liberty server as well as the affinity separator. If the Clone ID is defined by the user, as explained in the liberty documentation at https://www.ibm.com/support/knowledgecenter/SSEQTP_8.5.5/com.ibm.websphere.wlp.doc/ae/twlp_admin_session_persistence.html, and if the affinity separator is the colon character (:) character, then no additional configuration is required. If that is not the case, then the following system properties can be used during server startup:

- coherence.web.liberty.suffix.separator – The affinity suffix separator. The default value is :.

- coherence.web.liberty.suffix – The clone id of the server. The default value is the value configured for the cloneId system property in the bootstrap.properties file as explained in the WebSphere Liberty documentation cited above.

3.2 Coherence*Web WebInstaller Ant Task

The Coherence*Web WebInstaller Ant task enables you to run the utility from within your existing Ant build files.

This section contains the following information:

- Using the Coherence*Web WebInstaller Ant Task

- Configuring the WebInstaller Ant Task

- WebInstaller Ant Task Examples

3.2.1 Using the Coherence*Web WebInstaller Ant Task

To use the Coherence*Web WebInstaller Ant task, add the task import statement illustrated below in to your Ant build file. In this example, ${coherence.home} refers to the root directory of your Coherence installation.

<taskdef name="cwi" classname="com.tangosol.coherence.misc.CoherenceWebAntTask">
<classpath>
<pathelement location="${coherence.home}/lib/webInstaller.jar"/>
</classpath>
</taskdef>

The following procedure describes the basic process of integrating Coherence*Web with a Java EE application from an Ant build:

1. Build your Java EE application as you ordinarily would.

2. Run the Coherence*Web Ant task with the operations attribute set to inspect.

3. Make any necessary changes to the generated Coherence*Web XML descriptor file.

4. Run the Coherence*Web Ant task with the operations attribute set to install.

Performing Iterative Development

If you are performing iterative development on your application, such as modifying JavaServer Pages (JSPs), Servlets, static resources, and so on, use the following integration process:

1. Run the Coherence*Web Ant task with the operations attribute set to uninstall, the failonerror attribute set to false, and the descriptor attribute set to the location of the previously generated Coherence*Web XML descriptor file (from Step 2 of "Using the Coherence*Web WebInstaller Ant Task").

2. Build your Java EE application as you ordinarily would.

3. Run the Coherence*Web Ant task with the operations attribute set to inspect, and the install and descriptor attributes set to the location of the previously generated Coherence*Web XML descriptor file (from Step 2 of "Using the Coherence*Web WebInstaller Ant Task").

Changing the Coherence*Web Configuration Settings of a Java EE Application

If you must change the Coherence*Web configuration settings of a Java EE application that is using Coherence*Web, follow these steps:

1. Run the Coherence*Web Ant task with the operations attribute set to uninstall and the descriptor attribute set to the location of the Coherence*Web XML descriptor file for the Java EE application.

2. Change the necessary configuration parameters in the Coherence*Web XML descriptor file.

3. Run the Coherence*Web Ant task with the operations attribute set to install and the descriptor attribute set to the location of the modified Coherence*Web XML descriptor file (from Step 2 of "Using the Coherence*Web WebInstaller Ant Task").

3.2.2 Configuring the WebInstaller Ant Task

Table 3-2 describes the attributes that can be used with the Coherence*Web WebInstaller Ant task.

Table 3-2 Coherence*Web WebInstaller Ant Task Attributes

Attribute

Description

Required?

app

Path to the target Java EE application. This can be a path to a WAR file, an EAR file, an expanded WAR directory, or an expanded EAR directory.

Yes, if the operations attribute is set to any value other than version.

backup

Path to a directory that holds a backup of the original target Java EE application. This attribute defaults to the directory that contains the Java EE application.

No

descriptor

Path to the Coherence*Web XML descriptor file. This attribute defaults to the coherence-web.xml file in the directory that contains the target Java EE application.

No

failonerror

Stops the Ant build if the Coherence*Web WebInstaller exits with a status other than 0. The default is true.

No

nowarn

Suppresses warning messages. This attribute can be either true or false. The default is false.

No

operations

A comma- or space-separated list of operations to perform; each operation must be one of inspect, install, uninstall, or version.

Yes

server

The alias of the target Java EE application server.

No

touch

Touches JSPs and TLDs that are modified by the Coherence*Web WebInstaller. This attribute can be either true, false, or M/d/y h:mm a' The default is false.

No

verbose

Displays verbose output. This attribute can be either true or false. The default is false.

No

3.2.3 WebInstaller Ant Task Examples

The following list provides sample commands for the WebInstaller Ant task.

- Inspect the myWebApp.war Web application and generate a Coherence*Web XML descriptor file called my-coherence-web.xml in the current working directory:

<cwi app="myWebApp.war" operations="inspect" descriptor="my-coherence-web.xml"/>

- Integrate Coherence*Web into the myWebApp.war Web application using the Coherence*Web XML descriptor file called my-coherence-web.xml found in the current working directory:

<cwi app="myWebApp.war" operations="install" descriptor="my-coherence-web.xml"/>

- Remove Coherence*Web from the myWebApp.war Web application:

<cwi app="myWebApp.war" operations="uninstall">

- Integrate Coherence*Web into the myWebApp.war Web application located in the /dev/myWebApp/build directory using the Coherence*Web XML descriptor file called my-coherence-web.xml found in the /dev/myWebApp/src directory, and place a backup of the original Web application in the /dev/myWebApp/work directory:

<cwi app="/dev/myWebApp/build/myWebApp.war" operations="install" descriptor="/dev/myWebApp/src/my-coherence-web.xml" backup="/dev/myWebApp/work"/>

- Integrate Coherence*Web into the myWebApp.war Web application located in the /dev/myWebApp/build directory using the Coherence*Web XML descriptor file called coherence-web.xml found in the /dev/myWebApp/build directory. If the Web application has not already been inspected (that is, /dev/myWebApp/build/coherence-web.xml does not exists); inspect the Web application before integrating Coherence*Web:

<cwi app="/dev/myWebApp/build/myWebApp.war" operations="inspect,install"/>

- Reintegrate Coherence*Web into the myWebApp.war Web application located in the /dev/myWebApp/build directory, using the Coherence*Web XML descriptor file called my-coherence-web.xml found in the /dev/myWebApp/src directory:

<cwi app="/dev/myWebApp/build/myWebApp.war" operations="uninstall,install" descriptor="/dev/myWebApp/src/my-coherence-web.xml"/>

3.3 Testing HTTP Session Management

Coherence comes with a lightweight software load balancer; it is intended only for testing purposes. The load balancer is very easy to use and is very useful when testing functionality such as session management. Follow these steps to test HTTP session management with the lightweight load balancer:

1. Start multiple application server processes on one or more server machines, each running your application on a unique IP address and port combination.

2. Open a command (or shell) window.

3. Change the current directory to the Coherence library directory (%COHERENCE_HOME%\lib on Windows and $COHERENCE_HOME/lib on UNIX).

4. Ensure that paths are configured so that Java commands will run.

5. Start the software load balancer with the following command lines (each of these command lines makes the application available on the default HTTP port 80).

For example, to test load balancing locally on one machine with two application server instances on ports 7001 and 7002:

java -jar coherence-loadbalancer.jar localhost:80 localhost:7001 localhost:7002

To run the load balancer locally on a machine named server1 that load balances to port 7001 on server1, server2, and server3:

java -jar coherence-loadbalancer.jar server1:80 server1:7001 server2:7001 server3:7001

Assuming that you use the preceding command line, an application that previously was accessed with the URL http://server1:7001/my.jsp would now be accessed with the URL http://server1:80/my.jsp or just http://server1/my.jsp.

Note:

Ensure that your application uses only relative redirections or the address of the load balancer.

Table 3-3 describes the command-line options for the load balancer:

Table 3-3 Load Balancer Command-Line Options

Option

Description

backlog

Sets the TCP/ IP accept backlog option to the specified value, for example: -backlog=64.

random

Specifies the use of a random load-balancing algorithm (default).

roundrobin

Specifies the use of a round-robin load-balancing algorithm.

threads

Uses the specified number of request or response thread pairs (so the total number of additional daemon threads will be two times the specified value), for example: -threads=64.

3.4 How the Coherence*Web WebInstaller Instruments a Java EE Application

During the inspection step, the Coherence*Web WebInstaller performs the following tasks:

1. Generates a template coherence-web.xml configuration file that contains basic information about the application and target Web container along with a set of default Coherence*Web configuration context parameters appropriate for the target Web container. See Coherence*Web Context Parameters for descriptions of all possible parameters.
The WebInstaller sets the servlet container to start in storage-disabled mode (that is, it sets coherence.session.localstorage to false).

If an existing coherence-web.xml configuration file exists (for example, from a previous run of the Coherence*Web WebInstaller), the context parameters in the existing file are merged with those in the generated template.

2. Enumerates the JSP from each Web application in the target Java EE application and adds information about each JSP to the coherence-web.xml configuration file.

3. Enumerates the TLDs from each Web application in the target Java EE application and adds information about each TLD to the coherence-web.xml configuration file.

During the integration step, the Coherence*Web WebInstaller performs the following tasks:

1. Creates a backup of the original Java EE application so that it can be restored during the uninstallation step.

2. Adds the Coherence*Web configuration context parameters generated in Step 1 of the inspection step to the web.xml descriptor file of each Web application contained in the target Java EE application.

3. Unregisters any application-specific ServletContextListener, ServletContextAttributeListener, ServletRequestListener, ServletRequestAttributeListener, HttpSessionListener, and HttpSessionAttributeListener classes (including those registered by TLDs) from each Web application.

4. Registers a Coherence*Web ServletContextListener class in each web.xml descriptor file. At run time, the Coherence*Web ServletContextListener class propagates each ServletContextEvent event to each application-specific ServletContextListener listener.

5. Registers a Coherence*Web ServletContextAttributeListener listener in each web.xml descriptor file. At run time, the Coherence*Web ServletContextAttributeListener propagates each ServletContextAttributeEvent event to each application-specific ServletContextAttributeListener listener.

6. Wraps each application-specific Servlet declared in each web.xml descriptor file with a Coherence*Web SessionServlet. At run time, each Coherence*Web SessionServlet delegates to the wrapped Servlet.

7. Adds the following directive to each JSP enumerated in Step 2 of the inspection step:

<%@ page extends="com.tangosol.coherence.servlet.api22.JspServlet" %>

During the uninstallation step, the Coherence*Web WebInstaller replaces the instrumented Java EE application with the backup of the original version created in Step (1) of the integration process.

3.5 Integrating Coherence*Web with Applications Using Java EE Security

To integrate Coherence*Web with an application that uses Java EE security, follow these additional steps:

1. Enable Coherence*Web session cookies.

See the coherence-session-cookies-enabled configuration element in Table A-1 for additional details.

2. Change the Coherence*Web session cookie name to a name that is different from the one used by the target Web container.

By default, most containers use JSESSIONID for the session cookie name, so a good choice for the Coherence*Web session cookie name is CSESSIONID. See the coherence-session-cookie-name configuration element in Table A-1 for additional details.

3. Enable session replication for the target Web container.

If session replication is not enabled, or the container does not support a form of session replication, then you will be forced to re-authenticate to the Web application during failover. See your Web container's documentation for instructions on enabling session replication.

This configuration causes two sessions to be associated with a given authenticated user:

- A Coherence*Web session that contains all session data created by the Web application

- A session created by the Web container during authentication that stores only information necessary to identify the user

3.6 Preventing Cross-Site Scripting Attacks

Use the coherence-session-cookie-httponly context parameter to append the HttpOnly attribute to the session cookie. The HttpOnly attribute is used to help prevent attacks such as cross-site scripting, since it does not allow the cookie to be accessed by a client-side script such as JavaScript. Note that not all browsers support this functionality. This context parameter is available for instrumented applications only.

4 Coherence*Web Session Management Features

This chapter describes the features of Coherence*Web, including session models, session scoping, session locking, deployment topologies, and logging. You can configure Coherence*Web in many ways to meet the demands of your environment. Consequently, you might have to change some default configuration options. This chapter provides an in-depth look at the features that Coherence*Web supports so that you can make the appropriate configuration and deployment decisions.

- Session Models, which describes how Coherence*Web stores session state

- Session and Session Attribute Scoping, which allows fine-grained control over how both session data and session attributes are scoped (or shared) across application boundaries

- Cluster Node Isolation, which determines the number of Coherence nodes that are created within an application server JVM and where the Coherence library is deployed in the application's classpath

- Session Locking Modes, which determines how applications will obtain concurrent access to HTTP sessions

- Deployment Topologies, which determines how the session data is stored and managed between the cache servers and application servers

- Accessing Sessions with Lazy Acquisition, which describes how to save processing time and power by directing Coherence*Web to acquire sessions only when the servlet or filter attempts to access it

- Overriding the Distribution of HTTP Sessions and Attributes, which describes how you can control whether a session or its attributes remain local (stored on the originating server's heap and accessible only by that server) or distributed (stored within the Coherence grid, and thus, accessible to other server JVMs)

- Detecting Changed Attribute Values, which describes how Coherence*Web tracks attributes retrieved from the session that may have changed during the course of processing a request

- Saving Non-Serializable Attributes Locally, which describes how Coherence*Web can handle session attributes that are not serializable.

- Securing Coherence*Web Deployments, which describes how to prevent unauthorized Coherence TCMP cluster members from accessing HTTP session cache servers by enabling Secure Socket Layer (SSL).

- Customizing the Name of the Session Cache Configuration File, which describes how you can choose a custom name for your session cache configuration file.

- Configuring Logging for Coherence*Web, which describes the types of logging which are supported for Coherence*Web.

- Getting Concurrent Access to the Same Session Instance, which describes how you can use a cache delegator to ensure that the local cache should be used for storing and retrieving the session instance before attempting to use the distributed cache.

- Federated Session Caches, which describes how you can replicate sessions caches across Coherence cluster participants.

4.1 Session Models

A session model describes how Coherence*Web stores the session state in Coherence. Session data is managed by an HttpSessionModel object while the session collection in a Web application is managed by an HttpSessionCollection object. You must configure only the collection type in the web.xml file—the model is implicitly derived from the collection type. Coherence*Web includes these different session model implementations:

- Monolithic Model, which stores all session state as a single entity, serializing and deserializing all attributes as a single operation

- Traditional Model, which stores all session state as a single entity but serializes and deserializes attributes individually

- Split Model, which extends the Traditional Model, but separates the larger session attributes into independent physical entities

These sections provide additional information on session models:

- Session Model Recommendations, provides recommendations on which session model to choose for your applications

- Configuring a Session Model, describes how to change the session model by using a system property or a context parameter

- Sharing Data in a Clustered Environment, describes how data is shared between and within JVMs

- Scalability and Performance. describes the impact of session models on scalability and performance

Note:

In general, Web applications that are part of the same Coherence cluster must use the same session model type. Inconsistent configurations could result in deserialization errors.

Figure 4-1 illustrates the three session models.

Figure 4-1 Traditional, Monolithic, and Split Session Models

4.1.1 Monolithic Model

The Monolithic model is represented by the MonolithicHttpSessionModel and MonolithicHttpSessionCollection objects. These are similar to the Traditional model, except that they solve the shared object issue by serializing and deserializing all attributes into a single object stream. As a result, the Monolithic model often does not perform as well as the Traditional model.

Figure 4-2 illustrates the relationship between the logical representation of data and its physical representation in the session storage cache. In its logical representation session data consists of metadata, and various attributes. In its physical representation in the session storage cache, the metadata and attributes are serialized into a single stream. A session ID is associated with the metadata and attributes.

Figure 4-2 Monolithic Session Model

4.1.2 Traditional Model

The Traditional model is represented by the TraditionalHttpSessionModel and TraditionalHttpSessionCollection objects. The TraditionalHttpSessionCollection object stores an HTTP session object in a single cache, but serializes each attribute independently.

This model is suggested for applications with relatively small HTTP session objects (10 KB or less) that do not have issues with object sharing between session attributes. Object sharing between session attributes occurs when multiple attributes of a session have references to the same exact object, meaning that separate serialization and deserialization of those attributes cause multiple instances of that shared object to exist when the HTTP session is later deserialized.

Figure 4-3 illustrates the relationship between the logical representation of data and its physical representation in the session storage cache. In its logical representation session data consists of metadata, and various attributes. In its physical representation in the session storage cache, the metadata and attributes are converted to binaries, and a session ID is associated with them. Note that the attributes are serialized individually instead of as a single binary BLOB (such as in the Monolithic case).

Figure 4-3 Traditional Session Model

4.1.3 Split Model

The Split model is represented by the SplitHttpSessionModel and SplitHttpSessionCollection objects. SplitHttpSessionCollection is the default used by Coherence*Web.

These models store the core HTTP session metadata and all of the small session attributes in the same manner as the Traditional model, thus ensuring high performance by keeping that block of binary session data small. All large attributes are split into separate cache entries to be managed individually, thus supporting very large HTTP session objects without unduly increasing the amount of data that must be accessed and updated within the cluster for each request. In other words, only the large attributes that are modified within a particular request incur any network overhead for their updates, and (because it uses near caching) the Split model generally does not incur any network overhead for accessing either the core HTTP session data or any of the session attributes.

Figure 4-4 illustrates the relationship between the logical representation of data and its physical representation in the session storage cache. In this model, large objects are stored as separate cache entries with their own session ID.

Figure 4-4 Split Session Model

4.1.4 Session Model Recommendations

The following are recommendations on which session model to choose for your applications:

- The Split model is the recommended session model for most applications.

- The Traditional model might be more optimal for applications that are known to have small HTTP session objects.

- The Monolithic model is designed to solve a specific class of problems related to multiple session attributes that have references to the same shared object, and that must maintain that object as a shared object.

Note:

See Coherence*Web Context Parameters for descriptions of the parameters used to configure session models.

4.1.5 Configuring a Session Model

By default, Coherence*Web uses the split session model, where large attributes are split into separate cache entries to be managed individually. You can change the session model used by Coherence*Web by configuring the -Dcoherence.sessioncollection.class system property or by setting the equivalent coherence-sessioncollection-class context parameter in the Web application's web.xml file. As the value of the context parameter (or system property), use the fully-qualified class name of the HttpSessionCollection implementation.

- com.tangosol.coherence.servlet.SplitHttpSessionCollection (default) configures the Split model.

- com.tangosol.coherence.servlet.MonolithicHttpSessionCollection configures the Monolithic model.

- com.tangosol.coherence.servlet.TraditionalHttpSessionCollection configures the Traditional model.

Example 4-1 illustrates a web.xml entry to configure the Monolithic model.

Example 4-1 Configuring the Session Model

...
<context-param>
<param-name>coherence-sessioncollection-class</param-name>
<param-value>com.tangosol.coherence.servlet.MonolithicHttpSessionCollection</param-value>
</context-param>
...

4.1.6 Sharing Data in a Clustered Environment

Clustering can boost scalability and availability for applications. Clustering solutions such as Coherence*Web solve many problems for developers, but successful developers must be aware of the limitations of the underlying technology, and how to manage those limitations. Understanding what the platform provides, and what users require, gives developers the ability to eliminate the gap between the two.

Session attributes must be serializable if they are to be processed across multiple JVMs, which is a requirement for clustering. It is possible to make some fields of a session attribute non-clustered by declaring those fields as transient. While this eliminates the requirement for all fields of the session attributes to be serializable, it also means that these attributes are not fully replicated to the backup server(s). Developers who follow this approach should be very careful to ensure that their applications are capable of operating in a consistent manner even if these attribute fields are lost. In most cases, this approach ends up being more difficult than simply converting all session attributes to serializable objects. However, it can be a useful pattern when very large amounts of user-specific data are cached in a session.

The Java EE Servlet specification (versions 2.2, 2.3, and 2.4) states that the servlet context should not be shared across the cluster. Non-clustered applications that rely on the servlet context as a singleton data structure have porting issues when moving to a clustered environment.

A more subtle issue that arises in clustered environments is the issue of object sharing. In a non-clustered application, if two session attributes reference a common object, changes to the shared object are visible as part of both session attributes. However, this is not the case in most clustered applications. To avoid unnecessary use of compute resources, most session management implementations serialize and deserialize session attributes individually on demand. Coherence*Web (Traditional and Split session models) normally operates in this manner. If two session attributes that reference a common object are separately deserialized, the shared common object is instantiated twice. For applications that depend on shared object behavior and cannot be readily corrected, Coherence*Web provides the option of a Monolithic session model, which serializes and deserializes the entire session object as a single operation. This provides compatibility for applications that were not originally designed with clustering in mind.

Many projects require sharing session data between different Web applications. The challenge that arises is that each Web application typically has its own class loader. Consequently, objects cannot readily be shared between separate Web applications. There are two general methods used as a work around, each with its own set of trade-offs.

- Place common classes in the Java CLASSPATH, allowing multiple applications to share instances of those classes at the expense of a slightly more complicated configuration.

- Use Coherence*Web to share session data across class loader boundaries. Each Web application is treated as a separate cluster member, even if they run within the same JVM. This approach provides looser coupling between Web applications (assuming serialized classes share a common serial Version UID), but suffers from a performance impact because objects must be serialized-deserialized for transfer between cluster members.

4.1.7 Scalability and Performance

Moving to a clustered environment makes session size a critical consideration. Memory usage is a factor regardless of whether an application is clustered or not, but clustered applications must also consider the increased CPU and network load that larger sessions introduce. While non-clustered applications using in-memory sessions are not required to serialize-deserialize session state, clustered applications must do this every time session state is updated. Serializing session state and then transmitting it over the network becomes a critical factor in application performance. For this reason and others, a server should generally limit session size to no more than a few kilobytes.

While the Traditional and Monolithic session models for Coherence*Web have the same limiting factor, the Split session model was explicitly designed to efficiently support large HTTP sessions. Using a single clustered cache entry to contain all of the small session attributes means that network traffic is minimized when accessing and updating the session or any of its smaller attributes. Independently deserializing each attribute means that CPU usage is minimized. By splitting out larger session attributes into separate clustered cache entries, Coherence*Web ensures that the application only pays the cost for those attributes when they are actually accessed or updated. Additionally, because Coherence*Web leverages the data management features of Coherence, all of the underlying features are available for managing session attributes, such as near caching, NIO buffer caching, and disk-based overflow.

Figure 4-5 illustrates performance as a function of session size. Each session consists of ten 10-character Strings and from zero to four 10,000-character Strings. Each HTTP request reads a single small attribute and a single large attribute (for cases where there are any in the session), and 50 percent of requests update those attributes. Tests were performed on a two-server cluster. Note the similar performance between the Traditional and Monolithic models; serializing-deserializing Strings consumes minimal CPU resources, so there is little performance gain from deserializing only the attributes that are actually used. The performance gain of the Split model increases to over 37:1 by the time session size reaches one megabyte (100 large Strings). In a clustered environment, it is particularly true that application requests that access only essential data have the opportunity to scale and perform better; this is part of the reason that sessions should be kept to a reasonable size.

Figure 4-5 Performance as a Function of Session Size

Another optimization is the use of transient data members in session attribute classes. Because Java serialization routines ignore transient fields, they provide a very convenient means of controlling whether session attributes are clustered or isolated to a single cluster member. These are useful in situations where data can be "lazy loaded" from other data sources (and therefore recalculated during a server failover process), and also in scenarios where absolute reliability is not critical. If an application can withstand the loss of a portion of its session state with zero (or acceptably minimal) impact on the user, then the performance benefit may be worth considering. In a similar vein, it is not uncommon for high-scale applications to treat session loss as a session timeout, requiring the user to log back in to the application (which has the implicit benefit of properly setting user expectations regarding the state of their application session).

Sticky load balancing plays a critical role because session state is not globally visible across the cluster. For high-scale clusters, user requests normally enter the application tier through a set of stateless load balancers, which redistribute (more or less randomly) these requests across a set of sticky load balancers, such as Microsoft IIS or Apache HTTP Server. These sticky load balancers are responsible for the more computationally intense act of parsing the HTTP headers to determine which server instance is processing the request (based on the server ID specified by the session cookie). If requests are misrouted for any reason, session integrity is lost. For example, some load balancers may not parse HTTP headers for requests with large amounts of POST data (for example, more than 64KB), so these requests are not routed to the appropriate server instance. Other causes of routing failure include corrupted or malformed server IDs in the session cookie. Most of these issues can be handled with proper selection of a load balancer and designing tolerance into the application whenever possible (for example, ensuring that all large POST requests avoid accessing or modifying session state).

Sticky load balancing aids the performance of Coherence*Web but is not required. Because Coherence*Web is built on the Coherence data management platform, all session data is globally visible across the cluster. A typical Coherence*Web deployment places session data in a near cache topology, which uses a partitioned cache to manage huge amounts of data in a scalable and fault-tolerant manner, combined with local caches in each application server JVM to provide instant access to commonly used session state. While a sticky load balancer is not required when Coherence*Web is used, there are two key benefits to using one. Due to the use of near cache technology, read access to session attributes is instant if user requests are consistently routed to the same server, as using the local cache avoids the cost of deserialization and network transfer of session attributes. Additionally, sticky load balancing allows Coherence to manage concurrency locally, transferring session locks only when a user request is rebalanced to another server.

4.2 Session and Session Attribute Scoping

Coherence*Web allows fine-grained control over how both session data and session attributes are scoped (or shared) across application boundaries.

4.2.1 Session Scoping

Coherence*Web allows session data to be shared by different Web applications deployed in the same or different Web containers. To do so, you must correctly configure the session cookie context parameters and make the classes of objects stored in session attributes available to each Web application.

If you are using cookies to store session IDs (that is, you are not using URL rewriting), you must set the session cookie path to a common context path for all Web applications that share session data. For example, to share session data between two Web applications registered under the context paths /web/HRPortal and /web/InWeb, you should set the coherence-session-cookie-path parameter to /web. On the other hand, if the two Web applications are registered under the context paths /HRPortal and /InWeb, you should set the coherence-session-cookie-path parameter to a slash (/).

If the Web applications that you would like to share session data are deployed on different Web containers running on different machines (that are not behind a common load balancer), you must also configure the session cookie domain to a domain shared by the machines. For example, to share session data between two Web applications running on server1.mydomain.com and server2.mydomain.com, you must set the coherence-session-cookie-domain context parameter to .mydomain.com.

To correctly serialize or deserialize objects stored in shared sessions, the classes of all objects stored in session attributes must be available to Web applications that share session data.

Note:

For advanced use cases where EAR cluster node-scoping or application server JVM cluster scoping is employed and you do not want session data shared across individual Web applications, see "Preventing Web Applications from Sharing Session Data".

4.2.1.1 Preventing Web Applications from Sharing Session Data

Sometimes you might want to explicitly prevent HTTP session data from being shared by different Java EE applications that participate in the same Coherence cluster. For example, assume you have two applications, HRPortal and InWeb, that share cached data in their Enterprise JavaBeans (EJB) tiers but use different session data. In this case, it is desirable for both applications to be part of the same Coherence cluster, but undesirable for both applications to use the same clustered service for session data. One way to do this is to use the ApplicationScopeController interface to define the scope of an application's attributes. "Session Attribute Scoping" describes this technique. Another way is to specify a unique session cache service name for each application.

Follow these steps to specify a unique session cache service name for each application:

1. Locate the <service-name/> elements in each default-session-cache-config.xml file found in your application.

2. Set the elements to a unique value for each application.

This forces each application to use a separate clustered service for session data.

3. Include the modified default-session-cache-config.xml file with the application.

Example 4-2 illustrates a sample default-session-cache-config.xml file for an HRPortal application. To prevent the HRPortal application from sharing session data with the InWeb application, rename the <service-name> element for the replicated scheme to ReplicationSessionsMiscHRP. Rename the <service-name> element for the distributed schemes to DistributedSessionsHRP.

Example 4-2 Configuration to Prevent Applications from Sharing Session Data

<replicated-scheme>
<scheme-name>default-replicated</scheme-name>
<service-name>ReplicatedSessionsMisc</service-name> // rename this to ReplicatedSessionsMiscHRP
<backing-map-scheme>
<class-scheme>
<scheme-ref>default-backing-map</scheme-ref>
</class-scheme>
</backing-map-scheme>
</replicated-scheme>

<distributed-scheme>
<scheme-name>session-distributed</scheme-name>
<service-name>DistributedSessions</service-name> // rename this to DistributedSessionsHRP
<lease-granularity>member</lease-granularity>
<backing-map-scheme>
<class-scheme>
<scheme-ref>default-backing-map</scheme-ref>
</class-scheme>
</backing-map-scheme>
</distributed-scheme>

<distributed-scheme>
<scheme-name>session-certificate</scheme-name>
<service-name>DistributedSessions</service-name> // rename this to DistributedSessionsHRP
<lease-granularity>member</lease-granularity>
<backing-map-scheme>
<local-scheme>
<scheme-ref>session-certificate-autoexpiring</scheme-ref>
</local-scheme>
</backing-map-scheme>
</distributed-scheme>

4.2.1.2 Working with Multiple Cache Configurations

If you are working with two or more applications running under Coherence*Web, then they could have multiple different cache configurations. In this case, the cache configuration on the cache server must contain the union of these cache configurations regardless of whether you run in storage-enabled or storage-disabled mode. This will allow the applications to be supported in the same cache cluster.

4.2.1.3 Keeping Session Cookies Separate

If you are using cookies to store session IDs, you must ensure that session cookies created by one application are not propagated to another application. To do this, you must set each application's session cookie domain and path in their web.xml file. To prevent cookies from being propagated, ensure that no two applications share the same context path.

For example, assume you have two Web applications registered under the context paths /web/HRPortal and /web/InWeb. To prevent the Web applications from sharing session data through cookies, set the cookie path to /web/HRPortal in one application, and set the cookie path to /web/InWeb in the other application.

If your applications are deployed on different Web containers running on separate machines, then you can configure the cookie domain to ensure that they are not in the same domain.

For example, assume you have two Web applications running on server1.mydomain.com and server2.mydomain.com. To prevent session cookies from being shared between them, set the cookie domain in one application to server1.mydomain.com, and set the cookie domain in the other application to server2.mydomain.com.

4.2.2 Session Attribute Scoping

In the case where sessions are shared across Web applications there are many instances where the application might scope individual session attributes so that they are either globally visible (that is, all Web applications can see and modify these attributes) or scoped to an individual Web application (that is, not visible to any instance of another application).

Coherence*Web provides the ability to control this behavior by using the AttributeScopeController interface. This optional interface can selectively scope attributes in cases when a session might be shared across multiple applications. This allows different applications to potentially use the same attribute names for the application-scope state without accidentally reading, updating, or removing other applications' attributes. In addition to having application-scoped information in the session, this interface allows the session to contain global (unscoped) information that can be read, updated, and removed by any of the applications that shares the session.

Two implementations of the AttributeScopeController interface are available: ApplicationScopeController and GlobalScopeController. The GlobalScopeController implementation does not scope attributes, while ApplicationScopeController scopes all attributes to the application by prefixing the name of the application to all attribute names.

Use the coherence-application-name context parameter to specify the name of the application (and the Web module in which the application appears). The ApplicationScopeController interface will use the name of the application to scope the attributes. If you do not configure this parameter, then Coherence*Web uses the name of the class loader instead. For more information, see the description of coherence-application-name in Table 2-1.

Note:

After a configured AttributeScopeController implementation is created, it is initialized with the name of the Web application, which it can use to qualify attribute names. Use the coherence-application-name context parameter to configure the name of your Web application.

4.2.2.1 Sharing Session Information Between Multiple Applications

Coherence*Web allows multiple applications to share the same session object. To do this, the session attributes must be visible to all applications. You must also specify which URLs served by WebLogic Server will be able to receive cookies.

To allow the applications to share and modify the session attributes, reference the GlobalScopeController (com.tangosol.coherence.servlet.AbstractHttpSessionCollection$GlobalScopeController) interface as the value of the coherence-scopecontroller-class context parameter in the web.xml file. GlobalScopeController is an implementation of the com.tangosol.coherence.servlet.HttpSessionCollection$AttributeScopeController interface that allows individual session attributes to be globally visible.

Example 4-3 illustrates the GlobalScopeController interface specified in the web.xml file.

Example 4-3 GlobalScopeController Specified in the web.xml File

<?xml version="1.0" encoding="UTF-8"?>  <web-app>    ...
<context-param>
<param-name>coherence-scopecontroller-class</param-name>
<param-value>com.tangosol.coherence.servlet. AbstractHttpSessionCollection$GlobalScopeController</param-value>
</context-param>
...
</web-app>

4.3 Cluster Node Isolation

There are several different ways in which you can deploy Coherence*Web. One of the things to consider when deciding on a deployment option is cluster node isolation. Cluster node isolation considers:

- The number of Coherence nodes that are created within an application server JVM

- Where the Coherence library is deployed

Applications can be application server-scoped, EAR-scoped, or WAR-scoped. This section describes these considerations. For detailed information about the XML configuration for each of these options, see "Configure Coherence*Web Storage Mode".

4.3.1 Application Server-Scoped Cluster Nodes

With this configuration, all deployed applications in a container using Coherence*Web become part of one Coherence node. This configuration produces the smallest number of Coherence nodes in the cluster (one for each Web container JVM) and, because the Coherence library (coherence.jar) is deployed in the container's class path, only one copy of the Coherence classes is loaded into the JVM. This minimizes the use of resources. On the other hand, because all applications are using the same cluster node, all applications are affected if one application malfunctions.

Figure 4-6 illustrates an application server-scoped cluster with two cluster nodes (application server instances). Because Coherence*Web has been deployed to each instance's class path, each instance can be considered to be a Coherence node. Each node contains two EAR files; each EAR file contains two WAR files. All of the application running in each instance share the same Coherence library and classes.

Figure 4-6 Application Server-Scoped Cluster

For WebLogic Server, all Coherence*Web-enabled applications have application server scope by default. "Configure Coherence*Web Storage Mode" describes the XML configuration requirements for application server-scoped cluster nodes for WebLogic Server.

Note:

For platforms other than WebLogic Server, the use of application server-scoped cluster configurations should be used with care. Do not use it in environments where application interaction is unknown or unpredictable.

An example of such an environment might be a deployment where multiple application teams are deploying applications written independently, without carefully coordinating and enforcing their conventions and naming standards. With this configuration, all applications are part of the same cluster—the likelihood of collisions between namespaces for caches, services, and other configuration settings is quite high and could lead to unexpected results.

For these reasons, the recommended best practice is to use EAR-scoped and WAR-scoped cluster node configurations on platforms other than WebLogic Server. If you are in doubt regarding which deployment topology to choose, or if this note applies to your deployment, then do not choose the application server-scoped cluster node configuration.

4.3.2 EAR-Scoped Cluster Nodes

With this configuration, all deployed applications within each EAR file become part of one Coherence node. This configuration produces one Coherence node for each deployed EAR file that uses Coherence*Web. Because the Coherence library (coherence.jar) is deployed in the application's classpath, only one copy of the Coherence classes is loaded for each EAR file. Since all Web applications in the EAR file use the same cluster node, all Web applications in the EAR file are affected if one of the Web applications malfunctions.

Figure 4-7 illustrates four EAR-scoped cluster nodes. Since Coherence*Web has been deployed to each EAR file, each EAR file becomes a cluster node. All applications running inside each EAR file have access to the same Coherence libraries and classes.

Figure 4-7 EAR-Scoped Cluster

EAR-scoped cluster nodes reduce the deployment effort because no changes to the application server class path are required. This option is also ideal if you plan to deploy only one EAR file to an application server.

Note:

Applications running on the WebLogic Server platform should not use EAR-scoped cluster nodes.

4.3.3 WAR-Scoped Cluster Nodes

With this configuration, each deployed Web application becomes its own Coherence node. This configuration produces the largest number of Coherence nodes in the cluster (one for each deployed WAR file that uses Coherence*Web) and because the Coherence library (coherence.jar) is deployed in the Web application's class path, there will be as many copies of the Coherence classes loaded as there are deployed WAR files. This results in the largest resource utilization of the three options. However, because each deployed Web application is its own cluster node, Web applications are completely isolated from other potentially malfunctioning Web applications.

WAR -coped cluster nodes reduce the deployment effort because no changes to the application server class path are required. This option is also ideal if you plan to deploy only one WAR file to an application server.

Figure 4-8 illustrates two different configurations of WAR files in application servers. Because each WAR file contains a copy of Coherence*Web (and Coherence), it can be considered a cluster node.

Figure 4-8 WAR-Scoped Clusters

Note:

Applications running on the WebLogic Server platform should not use WAR-scoped cluster nodes.

4.4 Session Locking Modes

Oracle Coherence provides the following configuration options for concurrent access to HTTP sessions.

- Optimistic Locking, which allows concurrent access to a session by multiple threads in a single member or multiple members, while prohibiting concurrent modification.

- Last-Write-Wins Locking, which is a variation of Optimistic Locking. This allows concurrent access to a session by multiple threads in a single member or multiple members. In this case, the last write is saved. This is the default locking mode.

- Member Locking, which allows concurrent access and modification of a session by multiple threads in the same member, while prohibiting concurrent access by threads in different members.

- Application Locking, which allows concurrent access and modification of a session by multiple threads in the same Web application instance, while prohibiting concurrent access by threads in different Web application instances.

- Thread Locking, which prohibits concurrent access and modification of a session by multiple threads in a single member.

Note:

Generally, Web applications that are part of the same cluster must use the same locking mode and sticky session optimizations setting. Inconsistent configurations could result in deadlock.

You can specify the session locking mode used by your Web applications by setting the coherence-session-locking-mode context parameter. Table 4-1 lists the context parameter values and the corresponding session locking modes they specify. For more information about the coherence-session-locking-mode context parameter, see the following sections and Coherence*Web Context Parameters.

Table 4-1 Summary of coherence-session-locking-mode Context Parameter Values

Locking Mode

coherence-session-locking-mode Values

Optimistic Locking

optimistic

Last-Write-Wins Locking

none

Member Locking

member

Application Locking

app

Thread Locking

thread

4.4.1 Optimistic Locking

Optimistic Locking mode allows multiple Web container threads in one or more members to access the same session concurrently. This setting does not use explicit locking; rather an optimistic approach is used to detect and prevent concurrent updates upon completion of an HTTP request that modifies the session. The exception ConcurrentModificationException is thrown when the session is flushed to the cache, which is after the Servlet request has finished processing. To view the exception, set the weblogic.debug.DebugHttpSessions system property to true in the container's startup script (for example: -Dweblogic.debug.DebugHttpSessions=true).

The Optimistic Locking mode can be configured by setting the coherence-session-locking-mode parameter to optimistic.

4.4.2 Last-Write-Wins Locking

Coherence*Web is configured with Last-Write Wins Locking by default. Last-Write-Wins Locking mode is a variation on the Optimistic Locking mode. It allows multiple Web container threads in one or more members to access the same session concurrently. This setting does not use explicit locking; it does not prevent concurrent updates upon completion of an HTTP request that modifies the session. Instead, the last write, that is, the last modification made, is allowed to modify the session.

The Last-Write-Wins Locking mode can be configured by setting the coherence-session-locking-mode parameter to none. This value will allow concurrent modification to sessions with the last update being applied.

4.4.3 Member Locking

The Member Locking mode allows multiple Web container threads in the same cluster node to access and modify the same session concurrently, but prohibits concurrent access by threads in different members. This is accomplished by acquiring a member-level lock for an HTTP session when the session is acquired. The lock is released on completion of the of the HTTP request. For more information about member-level locks, see <lease-granularity> in the "distributed-scheme" section of Developing Applications with Oracle Coherence Oracle.

The Member Locking mode can be configured by setting the coherence-session-locking-mode parameter to member.

4.4.4 Application Locking

The Application Locking mode restricts session access (and modification) to threads in a single Web application instance at a time. This is accomplished by acquiring both a member-level and application-level lock for an HTTP session when the session is acquired, and releasing both locks upon completion of the HTTP request. For more information about member-level locks, see <lease-granularity> in the "distributed-scheme" section of Developing Applications with Oracle Coherence.

The Application Locking mode can be configured by setting the coherence-session-locking-mode parameter to app.

4.4.5 Thread Locking

Thread Locking mode restricts session access (and modification) to a single thread in a single member at a time. This is accomplished by acquiring both a member level, application-level, and thread-level lock for an HTTP session when the session is acquired, and releasing all three locks upon completion of the request. For more information about member-level locks, see <lease-granularity> in the "distributed-scheme" section of the Developing Applications with Oracle Coherence.

The Thread Locking mode can be configured by setting the coherence-session-locking-mode parameter to thread.

4.4.6 Troubleshooting Locking in HTTP Sessions

Enabling Member, Application, or Thread Locking for HTTP session access indicates that Coherence*Web will acquire a clusterwide lock for every HTTP request that requires access to a session. By default, threads that attempt to access a locked session (locked by a thread in a different member) block access until the lock can be acquired. If you want to enable a timeout for lock acquisition, configure it with the coherence-session-get-lock-timeout context parameter, for example:

...
<context-param>
<param-name>coherence-session-get-lock-timeout</param-name>
<param-value>30</param-value>
</context-param>
...

Many Web applications do not have such a strict concurrency requirement. For these applications, using the Optimistic Locking mode has the following advantages:

- The overhead of obtaining and releasing clusterwide locks for every HTTP request is eliminated.

- Requests can be load-balanced away from failing or unresponsive members to active members without requiring the unresponsive member to release the clusterwide lock on the session.

Coherence*Web provides a diagnostic invocation service that is executed when a member cannot acquire the cluster lock for a session. You can control if this service is enabled by setting the coherence-session-log-threads-holding-lock context parameter. If this context parameter is set to true (default), then the invocation service will cause the member that has ownership of the session to log the stack trace of the threads that are currently holding the lock.

Note that the coherence-session-log-threads-holding-lock context parameter is available only when the coherence-sticky-sessions context parameter is set to true. This requirement exists because Coherence Web will acquire a cluster-wide lock for every session access request unless sticky session optimization is enabled. By enabling sticky session optimization, frequent lock-holding, and the subsequent production of numerous log files, can be avoided.

Like all Coherence*Web messages, the Coherence logging-config operational configuration element controls how the message is logged. For more information on how to configure logging in Coherence, see the description of logging-config, in "Operation Configuration Elements" in Developing Applications with Oracle Coherence.

4.4.7 Enabling Sticky Session Optimizations

If Member, Application, or Thread Locking is a requirement for a Web application that resides behind a sticky load balancer, Coherence*Web provides an optimization for obtaining the clusterwide lock required for HTTP session access. By definition, a sticky load balancer attempts to route each request for a given session to the same application server JVM that it previously routed requests to for that same session. This should be the same application server JVM that created the session. The sticky session optimization takes advantage of this behavior by retaining the clusterwide lock for a session until the session expires or until it is asked to release it. If, for whatever reason, the sticky load balancer sends a request for the same session to another application server JVM, that JVM will ask the JVM that owns the lock on the session to release the lock as soon as possible. For more information, see the SessionOwnership entry in Table C-2.

Sticky session optimization can be enabled by setting the coherence-sticky-sessions context parameter to true. This setting requires that Member, Application, or Thread Locking is enabled.

4.5 Deployment Topologies

Coherence*Web supports most of the same deployment topologies that Coherence does including in-process, out-of-process (that is, client/server deployment), and bridging clients and servers over Coherence*Extend. The major supported deployment topologies are described in the following sections.

- In-Process Topology, also known as local storage enabled, is where session data is stored in-process with the application server

- Out-of-Process Topology, also known as local storage disabled, is where the application servers are configured as cache clients and dedicated JVMs run as cache servers, physically storing and managing the clustered data.

- Out-of-Process with Coherence*Extend Topology, means communication between the application server tier and the cache server tier are over Coherence*Extend (TCP/IP).

4.5.1 In-Process Topology

The in-process topology is not recommended for production use and is supported mainly for development and testing. By storing the session data in-process with the application server, this topology is very easy to get up and running quickly for smoke tests, developing and testing. In this topology, local storage is enabled (that is, coherence.distributed.localstorage=true).

Figure 4-9 illustrates the in-process topology. All of the application servers communicate with the same session data cache.

Figure 4-9 In-Process Deployment Topology

4.5.2 Out-of-Process Topology

For the out-of-process deployment topology, the application servers (that is, application server tier) are configured as cache clients (that is, coherence.distributed.localstorage=false) and there are dedicated JVMs running as cache servers, physically storing and managing the clustered data.

This approach has these benefits:

- Session data storage is offloaded from the application server tier to the cache server tier. This reduces heap usage, garbage collection times, and so on.

- The application and cache server tiers can be scaled independently. If more application processing power is needed, just start more application servers. If more session storage capacity is needed, just start more cache servers.

The Out-of-Process topology is the default recommendation of Oracle Coherence due to its flexibility. Figure 4-10 illustrates the out-of-process topology. Each of the servers in the application tier maintain their own near cache. These near caches communicate with the session data cache which runs in a separate cache server tier.

Figure 4-10 Out-of-Process Deployment Topology

4.5.2.1 Migrating from In-Process to Out-of-Process Topology

You can easily migrate your application from an in-process to an out of process topology. To do this, you must run a cache server in addition to the application server. Start the cache server in storage-enabled mode and ensure that it references the same session and cache configuration file (default-session-cache-config.xml) that the application server uses. Start the application server in storage-disabled mode. See "Migrating to Out-of-Process Topology" for detailed information.

4.5.3 Out-of-Process with Coherence*Extend Topology

Coherence*Extend consists of two components: an extend client (or proxy) running outside the cluster and an extend proxy service running in the cluster hosted by one or more cache servers. The out-of-process with Coherence*Extend topology is similar to the out-of-process topology except that the communication between the application server tier and the cache server tier is over Coherence*Extend (TCP/IP). For information about configuring this scenario, see "Configuring Coherence*Web with Coherence*Extend". For information about Coherence*Extend, see Developing Remote Clients for Oracle Coherence.

This approach has the same benefits as the out-of-process topology and the ability to divide the deployment of application servers and cache servers into segments. This is ideal in an environment where application servers are on a network that does not support UDP. The cache servers can be set up in a separate dedicated network, with the application servers connecting to the cluster by using TCP.

Figure 4-11 illustrates the out-of-process with Coherence*Extend topology. Near caches in the servers in the application server tier use an extend proxy to communicate with the session data cache in the cache server tier.

Figure 4-11 Out-of-Process with Coherence*Extend Deployment Topology

4.5.4 Configuring Coherence*Web with Coherence*Extend

One of the deployment options for Coherence*Web is to use Coherence*Extend to connect Web container JVMs to the cluster by using TCP/IP. This configuration should be considered if any of the following situations applies:

- The Web tier JVMs are in a DMZ while the Coherence cluster is behind a firewall.

- The Web tier is in an environment that does not support UDP.

- Web tier JVMs experience long or frequent garbage collection (GC) pauses.

- Web tier JVMs are restarted frequently.

In these deployments, there are three types of participants:

- Web tier JVMs, which are the Extend clients in this topology. They are not members of the cluster; instead, they connect to a proxy node in the cluster that will issue requests to the cluster on their behalf.

- Proxy JVMs, which are storage-disabled members (nodes) of the cluster that accept and manage TCP/IP connections from Extend clients. Requests that arrive from clients will be sent into the cluster, and responses will be sent back through the TCP/IP connections.

- Storage JVMs, which are used to store the actual session data in memory.

To Configure Coherence*Web to Use Coherence*Extend

1. Configure Coherence*Web to use the Optimistic Locking mode (see "Optimistic Locking").

2. Configure a cache configuration file for the proxy and storage JVMs (see "Configure the Cache for Proxy and Storage JVMs").

3. Modify the Web tier cache configuration file to point to one or more of the proxy JVMs (see "Configure the Cache for Web Tier JVMs").

4.5.4.1 Configure the Cache for Proxy and Storage JVMs

The session cache configuration file (WEB-INF/classes/default-session-cache-config.xml) is an example Coherence*Web session cache configuration file that uses Coherence*Extend. Use this file for the proxy and server JVMs. It contains system property overrides that allow the same file to be used for both proxy and storage JVMs.

When used by a proxy JVM, the system properties described in Table 4-2 should be specified.

Note:

If you are writing applications for the WebLogic Server platform and you are using a customized session cache configuration file, then the file must be packaged in a GAR file for deployment. For more information, see "Using a Custom Session Cache Configuration File".

For more information on the packaging requirements for a GAR file, see also "Packaging Coherence Applications for WebLogic Server" in Administering Oracle Coherence and "Creating Coherence Applications for Oracle WebLogic Server" in Developing Oracle Coherence Applications for Oracle WebLogic Server.

Table 4-2 System Property Values for Proxy JVMs

System Property Name

Value

coherence.session.localstorage

false

coherence.session.proxy

true

coherence.session.proxy.localhost

The host name or IP address of the NIC to which the proxy will bind.

coherence.session.proxy.localport

A unique port number to which the proxy will bind.

When used by a cache server, specify the system properties described in Table 4-3.

Table 4-3 System Property Values for Storage JVMs

System Property Name

Value

coherence.session.localstorage

true

coherence.session.proxy

false

4.5.4.2 Configure the Cache for Web Tier JVMs

Coherence*Extend clients must also include a session cache configuration file. The file can be based on the default-session-cache-config.xml file that is found in the coherence-web.jar file.

To Install the Session Cache Configuration File for the Web Tier:

1. Extract the default-session-cache-config.xml file from the coherence-web.jar file.

2. Add proxy JVM host names and IP addresses and ports within the <remote-addresses> element. In most cases, you should include the host name and IP address, and port of all proxy JVMs for load balancing and failover. For example:

<remote-cache-scheme>
<scheme-name>session-remote</scheme-name>
<initiator-config>
<serializer>
<instance>
<class-name>com.tangosol.io.DefaultSerializer</class-name>
</instance>
</serializer>
<tcp-initiator>
<remote-addresses>
<socket-address>
<address>localhost</address>
<port>9099</port>
</socket-address>
</remote-addresses>
</tcp-initiator>
</initiator-config>
</remote-cache-scheme>

Note:

The <remote-addresses> element contains the proxy server(s) to which the Web container connects. By default, the Web container will pick an address at random (if there is more than one address in the configuration). If the connection between the Web container and the proxy is broken, the container connects to another proxy in the list.

3. Rename the file to default-session-cache-config-web-tier.xml.

4. Place the file in the WEB-INF/classes directory of your Web application. If you used the WebInstaller to integrate Coherence*Web, replace the existing file that was added by the WebInstaller.

4.6 Accessing Sessions with Lazy Acquisition

By default, Web applications instrumented with the WebInstaller will always acquire a session whenever a servlet or filter is called. The session is acquired regardless of whether the servlet or filter actually needs a session. This can be expensive in terms of time and processing power if you run many servlets or filters that do not require a session.

To avoid this behavior, enable lazy acquisition by setting the coherence-session-lazy-access context parameter to true in the web.xml file. The session will be acquired only when the servlet or filter attempts to access it.

4.7 Overriding the Distribution of HTTP Sessions and Attributes

The Coherence*Web Session Distribution Controller, described by the HttpSessionCollection.SessionDistributionController interface, enables you to override the default distribution of HTTP sessions and attributes in a Web application. You override the default distribution by setting the coherence-distributioncontroller-class context parameter (see "Registering a Session Distribution Controller Implementation"). The value of the context parameter indicates an implementation of the SessionDistributionController interface.

An implementation of the SessionDistributionController interface can identify sessions or attributes in any of the following ways:

- Distributed, where a distributed session or attribute is stored within the Coherence data grid, and thus, accessible to other server JVMs. All sessions (and their attributes) are managed in a distributed manner. This is the default behavior and is provided by the com.tangosol.coherence.servlet.AbstractHttpSessionCollection$DistributedController implementation of the SessionDistributionController interface.

- Local, where a local session or attribute is stored on the originating server's heap, and thus, only accessible by that server. The com.tangosol.coherence.servlet.AbstractHttpSessionCollection$LocalController class provides this behavior. This option is not recommended for production purposes, but it can be useful for testing the difference in scalable performance between local-only and fully distributed implementations.

- Hybrid, which is similar to distributed in that all sessions and serializable attributes are managed in a distributed manner. However, unlike distributed, session attributes that do not implement the Serializable interface will be kept local. The com.tangosol.coherence.servlet.AbstractHttpSessionCollection$HybridController class provides this behavior.

At any point during the life of a session, the session or attributes for that session can change from local or distributed. However, when a session or attribute is distributed it cannot change back to local.

You can use the Session Distribution Controller in any of the following ways:

- You can allow new sessions to remain local until you add an attribute (for example, when you add the first item to an online shopping cart); the idea is that a session must be fault-tolerant only when it contains valuable data.

- Some Web frameworks use session attributes to store the UI rendering state. Often, this data cannot be distributed because it is not serializable. Using the Session Distribution Controller, these attributes can be kept local while allowing the rest of the session attributes to be distributed.

- The Session Distribution Controller can assist in the conversion from nondistributed to distributed systems, especially when the cost of distributing all sessions and all attributes is a consideration.

4.7.1 Implementing a Session Distribution Controller

Example 4-4 illustrates a sample implementation of the HttpSessionCollection.SessionDistributionController interface. In the sample, sessions are tested to see if they have a shopping cart attached (only these sessions will be distributed). Next, the session is tested whether it contains a certain attribute. If the attribute is found, then it is not distributed.

Example 4-4 Sample Session Distribution Controller Implementation

import com.tangosol.coherence.servlet.HttpSessionCollection;
import com.tangosol.coherence.servlet.HttpSessionModel;

/**
* Sample implementation of SessionDistributionController
*/
public class CustomSessionDistributionController
implements HttpSessionCollection.SessionDistributionController
{
public void init(HttpSessionCollection collection)
{
}

/**
* Only distribute sessions that have a shopping cart.
*
* @param model Coherence representation of the HTTP session
*
* @return true if the session should be distributed
*/
public boolean isSessionDistributed(HttpSessionModel model)
{
return model.getAttribute("shopping-cart") != null;
}

/**
* If a session is "distributed", then distribute all attributes with the
* exception of the "ui-rendering" attribute.
*
* @param model Coherence representation of the HTTP session
* @param sName name of the attribute to check
*
* @return true if the attribute should be distributed
*/
public boolean isSessionAttributeDistributed(HttpSessionModel model,
String sName)
{
return !"ui-rendering".equals(sName);
}
}

4.7.2 Registering a Session Distribution Controller Implementation

After you have written your SessionDistributionController implementation, you can register it with your application by using the coherence-distributioncontroller-class context parameter. See Coherence*Web Context Parameters for more information about this parameter.

4.8 Detecting Changed Attribute Values

By default, Coherence*Web tracks if attributes retrieved from the session have changed during the course of processing a request. This is done by caching the initial serialized binary form of the attribute when it is retrieved from the session. At the end of processing a request, Coherence*Web will compare the current binary value of the attribute with the "old" version of the binary. If the values do not match, then the current value is written to the cache.If you know that your application does not mutate session attributes without doing a corresponding set, then you should set the coherence-enable-suspect-attributes context parameter to false. This will improve memory use and near-cache optimization.

4.9 Saving Non-Serializable Attributes Locally

By default, Coherence*Web attempts to serialize all session attributes. If you are working with any session attributes that are not serializable, you can store them locally by setting the coherence-preserve-attributes parameter to true. This parameter requires you to use a load balancer to retrieve non-serializable attributes for a session.

Note that if the client (application server) fails, then the attributes will be lost. Your application must be able to recover from this.

See Coherence*Web Context Parameters for more information about the coherence-preserve-attributes parameter.

4.10 Securing Coherence*Web Deployments

To prevent unauthorized Coherence TCMP cluster members from accessing HTTP session cache servers, Coherence provides a Secure Socket Layer (SSL) implementation. This implementation can be used to secure TCMP communication between cluster nodes and TCP communication between Coherence*Extend clients and proxies. Coherence allows you to use the Transport Layer Security (TLS) 1.0 protocol which is the next version of the SSL 3.0 protocol; however, the term SSL is used since it is the more widely recognized term.

This section provides only an overview of using SSL in a Coherence environment. For more information and sample configurations, see "Using SSL to Secure Communication" in Securing Oracle Coherence.

Using SSL to Secure TCMP Communications

A Coherence cluster can be configured to use SSL with TCMP. Coherence allows you to use both one-way and two-way authentication. Two-Way authentication is typically used more often than one-way authentication, which has fewer use cases in a cluster environment. In addition, it is important to realize that TCMP is a peer-to-peer protocol that generally runs in trusted environments where many cluster nodes are expected to remain connected with each other. The implications of SSL on administration and performance should be carefully considered.

In this configuration, you can use the pre-defined, out-of-the-box SSL socket provider that allows for two-way communication SSL connections based on peer trust, or you can define your own SSL socket provider.

Using SSL to Secure Extend Client Communication

Communication between extend clients and extend proxies can be secured using SSL. SSL requires configuration on both the client side as well as the cluster side. On the cluster side, you configure SSL in the cluster-side cache configuration file by defining a SSL socket provider for a proxy service. You can define the SSL socket provider either for all proxy services or for individual proxy services.

On the client side, you configure SSL in the client-side cache configuration file by defining a SSL socket provider for a remote cache scheme and, if required, for a remote invocation scheme. Like the cluster side, you can define the SSL socket provider either for all remote services or for individual remote services.

4.11 Customizing the Name of the Session Cache Configuration File

By default, Coherence*Web uses the information in the default-session-cache-config.xml file to configure the session caches in Coherence*Web. You can direct Coherence*Web to use a different file by specifying the coherence-cache-configuration-path context parameter in the web.xml file, for example:

...
<context-param>
<param-name>coherence-cache-configuration-path</param-name>
<param-value>my-default-session-cache-config-name.xml</param-value>
</context-param>
...

4.12 Configuring Logging for Coherence*Web

Coherence*Web uses the logging framework provided by Coherence. Coherence has its own logging framework and also supports the use of log4j, slf4j, and Java logging to provide a common logging environment for an application. Logging in Coherence occurs on a dedicated and low-priority thread to reduce the impact of logging on the critical portions of the system. Logging is pre-configured and the default settings should be changed as required. For more information, see "Configuring Logging" in Developing Applications with Oracle Coherence.

The Coherence*Web logging level can also be set using the context parameter/system property coherence-session-logger-level. This is an alternative way to set the logging level for Coherence*Web (as opposed to using JDK logging). See Coherence*Web Context Parameters for more information on this parameter.

WARNING:

Applications that use the JDK logging framework can configure Coherence to use JDK logging as well. Note, however, that setting the log level to FINEST can expose session IDs in the log file.

4.13 Getting Concurrent Access to the Same Session Instance

A cache delegator class is a class that is responsible for manipulating (getting, putting, or deleting) any data in the distributed cache. Use the <coherence-cache-delegator-class> context parameter in the web.xml file to specify the name of the class responsible for the data manipulation.

One of the possible values for the context parameter is the com.tangosol.coherence.servlet.LocalSessionCacheDelegator class. This class indicates that the local cache should be used for storing and retrieving the session instance before attempting to use the distributed cache. This delegator is useful for applications that require concurrent access to the same session instance.

Note:

This feature must be enabled when working with PeopleSoft applications.

To enable the LocalSessionCacheDelegator cache delegator, the following items must be configured in web.xml:

- The coherence-cache-delegator-class context parameter with the value set to com.tangosol.coherence.servlet.LocalSessionCacheDelegator.

- The coherence-preserve-attributes context parameter set to true to allow nonserializable objects to be stored in the session object.

- The coherence-distributioncontroller-class context parameter with the value set to com.tangosol.coherence.servlet.AbstractHttpSessionCollection$HybridController. This value forces all sessions and serializable attributes to be managed in a distributed manner. All session attributes that do not implement the Serializable interface will be kept local. Note that the use of this context parameter also requires coherence-sticky-sessions optimization to be enabled.

Example 4-5 illustrates a sample configuration for the cache delegator in the web.xml file.

Example 4-5 Configuring Cache Delegator in the web.xml File

...
<context-param>
<param-name>coherence-cache-delegator-class</param-name>
<param-value>com.tangosol.coherence.servlet.LocalSessionCacheDelegator
</param-value>
</context-param>
<context-param>
<param-name>coherence-preserve-attributes</param-name>
<param-value>true</param-value>
</context-param>
<context-param>
<param-name>coherence-distributioncontroller-class</param-name>
<param-value>com.tangosol.coherence.servlet.AbstractHttpSessionCollection$HybridController</param-value>
</context-param>
...

4.14 Federated Session Caches

The Coherence federated caching feature replicates cache data asynchronously across multiple geographically dispersed clusters. Coherence*Web can take advantage of federated caching to provide redundancy, off-site backup, and multiple points of access for application users that are in different geographical locations. For details about Federated caching, see Administering Oracle Coherence.

To use federated caching for HTTP session caches:

1. Define federation cluster participants and a federation topology. For detailed instructions, see Configuring Cache Federation.

2. Enable federated caching for HTTP session management. For detailed instructions, see Enabling the Coherence Session Cache in WebLogic Server Administration Console.

3. Configure Coherence*Web to use a federated cache scheme. A default session cache configuration file is included in the coherence-web.jar library and is called default-federated-session-cache-config.xml session cache configuration file. To use the default federated session cache configuration file, use the coherence-session-cache-federated context parameter with the value set to true.

4. (Optional) The default federated topology that is configured is automatically used if no topology is configured, to explicitly specify a topology, update or override the default-federated-session-cache-config.xml session cache configuration file and associate the default federated caching scheme (session-distributed) with a federation topology. For detailed instructions, see Administering Oracle Coherence. For example:

<federated-scheme>
<scheme-name>session-distributed</scheme-name>
<service-name>FederatedDistributedSessions</service-name>
<thread-count system-property="coherence.session.threads">4
</thread-count>
<lease-granularity>member</lease-granularity>
<local-storage system-property="coherence.session.localstorage">
false</local-storage>
<partition-count>257</partition-count>
<backup-count>1</backup-count>
<request-timeout>30s</request-timeout>
<backing-map-scheme>
<ramjournal-scheme>
<high-units system-property="coherence.session.highunits"/>
<unit-calculator>BINARY</unit-calculator>
</ramjournal-scheme>
</backing-map-scheme>
<autostart>true</autostart>
<topologies>
<topology>
<name>MyTopology</name>
<cache-name>fed-remote</cache-name>
</topology>
</topologies>
</federated-scheme>

5 Monitoring Applications

This chapter describes how to use the provided JMX MBeans to monitor the health and performance of Coherence*Web on your system.It also describes how to run the Reporter—a JMX-based reporting utility that provides several preconfigured reports that help administrators and developers manage capacity and troubleshoot problems.

This chapter contains the following sections:

- Managing and Monitoring Applications with JMX

- Running Performance Reports

Note:

To enable Coherence*Web JMX Management and Monitoring, this section assumes that you have first set up the Coherence Clustered JMX Framework. To set up this framework, see the configuration and installation instructions in "Using JMX to Manage Coherence" in Managing Oracle Coherence.

5.1 Managing and Monitoring Applications with JMX

The management attributes and operations for Web applications that use Coherence*Web for HTTP session management are visible through the HttpSessionManagerMBean MBean (com.tangosol.coherence.servlet.management.HttpSessionManagerMBean).

During startup, each Coherence*Web Web application registers a single instance of the HttpSessionManager class. You can use a monitoring tool, such as JConsole, to view the values of the MBean attributes. The MBean is unregistered when the Web application shuts down.

Table 5-1 describes the object name that the MBean uses for registration.

Table 5-1 Object Name for HttpSessionManagerMBean

Managed Bean

Object Name

HttpSessionManager

type=HttpSessionManager, nodeId=cluster node id, appId=web application id

Table 5-2 describes the information that HttpSessionManager provides. All of the names represent attributes, except resetStatistics, which is an operation.

Several of the MBean attributes use the following prefixes:

- LocalSession, which indicates a session that is not distributed to all members of the cluster. The session remains local to the originating server until a later point in the life of the session.

- LocalAttribute, which indicates a session attribute that is not distributed to all members of the cluster.

- Overflow, a cache which stores the large session attributes when the Split Session model is used.

Table 5-2 Information Returned by the HttpSessionManager

Attribute Name

Data Type

Description

AverageReapDuration

long

The average reap duration (the time it takes to complete a reap cycle) in milliseconds, since the statistic was reset. See "Getting Session Reaper Performance Statistics".

CollectionClassName

String

The fully qualified class name of the HttpSessionCollection implementation in use. The HttpSessionCollection interface is an abstract model for a collection of HttpSessionModel objects. The interface is not at all affected by how the sessions communicate between the clients and the servers.

FactoryClassName

String

The fully-qualified class name of the Factory implementation being used. The SessionHelper.Factory class is used by the SessionHelper class to obtain objects that implement various important parts of the servlet specification. The Factory implementation can be placed in front of the application instead of the application server's own objects. This changes the apparent implementation of the application server itself (for example, adding clustering.)

LastReapDuration

long

The amount of time, in milliseconds, it took for the last reap cycle to finish. See "Getting Session Reaper Performance Statistics".

LocalAttributeCacheName

String

The name of the local cache that stores non-distributed session attributes. If the attribute displays null then local session attribute storage is disabled.

LocalAttributeCount

Integer

The number of non-distributed session attributes stored in the local session attribute cache. If the attribute displays -1, then local session attribute storage is disabled.

LocalSessionCacheName

String

The name of the local cache that stores nondistributed sessions. If the attribute displays a null value, then local session storage is disabled.

LocalSessionCount

Integer

The number of nondistributed sessions stored in the local session cache. If the attribute displays a -1 value, then local session storage is disabled.

MaxReapedSessions

long

The maximum number of sessions reaped in a reap cycle since the statistic was reset. See "Getting Session Reaper Performance Statistics".

NextReapCycle

java.lang.Date

The time, expressed as a java.lang.Date data type, for the next reap cycle. See "Getting Session Reaper Performance Statistics".

OverflowAverageSize

Integer

The average size (in bytes) of the session attributes stored in the overflow clustered cache since the last time statistics were reset. If the attribute displays -1, then a SplitHttpSessionCollection model is not in use.

OverflowCacheName

String

The name of the clustered cache that stores the large attributes that exceed a certain size and thus are determined to be more efficiently managed as separate cache entries and not as part of the serialized session object itself. A null value is displayed if a SplitHttpSessionCollection model is not in use.

OverflowMaxSize

Integer

The maximum size (in bytes) of a session attribute stored in the overflow clustered cache since the last time statistics were reset. The attribute displays a -1 value if a SplitHttpSessionCollection model is not in use.

OverflowThreshold

Integer

The minimum length (in bytes) that the serialized form of an attribute value must be stored in the separate overflow cache that is reserved for large attributes. The attribute displays a -1 value if a SplitHttpSessionCollection model is not in use.

OverflowUpdates

Integer

The number of updates to session attributes stored in the overflow clustered cache since the last time statistics were reset. The attribute displays a -1 value if a SplitHttpSessionCollection model is not in use.

ReapedSessions

long

The number of sessions reaped during the last cycle. See "Getting Session Reaper Performance Statistics".

ReapedSessionsTotal

long

The number of expired sessions that have been reaped since the statistic was reset. See "Getting Session Reaper Performance Statistics".

ServletContextCacheName

String

The name of the clustered cache that stores javax.servlet.ServletContext attributes. The attribute displays null if ServletContext is not clustered.

ServletContextName

String

The name of the Web application ServletContext.

SessionAverageLifetime

Integer

The average lifetime (in seconds) of session objects invalidated (either due to expiration or to an explicit invalidation) since the last time statistics were reset.

SessionAverageSize

Integer

The average size (in bytes) of session objects placed in the session storage clustered cache since the last time statistics were reset.

SessionCacheName

String

The name of the clustered cache that stores serialized session objects.

SessionIdLength

Integer

The length (in characters) of generated session IDs.

SessionMaxSize

Integer

The maximum size (in bytes) of a session object placed in the session storage clustered cache since the last time statistics were reset.

SessionMinSize

Integer

The minimum size (in bytes) of a session object placed in the session storage clustered cache since the last time statistics were reset.

SessionStickyCount

Integer

The number of session objects that belong to this instance of the Web application. The attribute displays -1 if sticky session optimizations are disabled.

SessionTimeout

Integer

The session expiration time (in seconds). The attribute displays -1 if sessions never expire.

SessionUpdates

Integer

The number of updates of session object stored in the session storage clustered cache since the last time statistics were reset.

resetStatistics (operation)

void

Reset the session management statistics.

Figure 5-1 illustrates the attributes of the HttpSessionManager MBean displayed in the JConsole monitoring tool.

Figure 5-1 HttpSessionManager Displayed in the JConsole Monitoring Tool

5.1.1 Managing and Monitoring Applications on WebLogic Server

For WebLogic Server, management attributes and operations for Web applications that use Coherence*Web for HTTP session management are visible through the WebLogicHttpSessionManagerMBean MBean (com.tangosol.coherence.servlet.management.WebLogicHttpSessionManagerMBean).

Table 5-3 describes the object name that the MBean uses for registration.

Table 5-3 Object Name for WebLogicHttpSessionManagerMBean

Managed Bean

Object Name

WebLogicHttpSessionManager

type=WebLogicHttpSessionManager, nodeId=cluster node id, appId=web application id

The WebLogicHttpSessionManager class extends the HttpSessionManager class. In addition to the information described in Table 5-2, the WebLogicHttpSessionManager class also returns the information listed in Table 5-4. Enterprise Manager uses this information to correlate the Coherence*Web instances to the server.

Table 5-4 Information Returned by the WebLogicHttpSessionManager MBean

Attribute Name

Data Type

Description

ApplicationId

String

The WebLogic Web application ID.

ApplicationName

String

The name of this Web application.

ApplicationVersion

String

The version of this Web application.

DomainName

String

The WebLogic domain name on which the application is deployed.

IsEar

Boolean

Displays true if this Web application is a module of an EAR file.

IsListenAddressEnabled

Boolean

Displays true if a HTTP port is available on this server.

IsSSLListenPortEnabled

Boolean

Displays true if a HTTPS port is available on this server.

ListenAddress

String

The address on which the server is listening.

ListenPort

Integer

The port on which this server listens for HTTP requests.

ServerName

String

The WebLogic Server name on which the application is deployed.

SSLListenPort

Integer

The port on which this server is listening for HTTPS requests.

5.2 Running Performance Reports

Note:

You can find a detailed discussion of the Reporter, including configuring the Reporter, running preconfigured reports, and creating custom reports, in the chapters under "Using JMX Reporting" in Managing Oracle Coherence.

Coherence includes a JMX-based reporting utility known as the Reporter. The Reporter provides several preconfigured reports that help administrators and developers manage capacity and troubleshoot problems. These reports are specially tuned for Coherence*Web:

- Web Session Storage Report, which records statistics about the activity between the cluster and the cache where the cluster's session objects and data are stored.

- Web Session Overflow Report, which records statistics about the activity between the cluster and the cache where session objects and data are allowed to overflow from the Web session storage cache.

- Web Report, which records information about Coherence*Web activity for the cluster.

- WebLogic Web Report, which is intended for WebLogic Server environments. This report provides the same information as Web Report, but includes the name of the WebLogic Server and the WebLogic Server domain.

- Web Service Report, which records information about the service running the Coherence*Web application.

The Coherence*Web reports should be run as part of a batch report. They are defined in both the report-web-group.xml and the comprehensive report-all.xml batch reports. You can also include them in a custom batch report. The Coherence*Web reports are not defined in the default report group batch file, report-group.xml.

The Reporter runs the report-group.xml batch report by default. Use the coherence.management.report.configuration system property to run report-web-group.xml, report-all.xml, or a custom batch report instead. Example 5-1 illustrates a command line where the property is used to change the report group batch file that is run to report-web-group.xml.

The report-web-group.xml, report-all.xml, and report-group.xml report group batch files, can be found in the reports folder in the coherence.jar file.

Example 5-1 Specifying a Report Group on the Command Line

java -Dcom.sun.management.jmxremote
-Dcoherence.management=all
-Dcoherence.management.remote=true
-Dcoherence.management.report.autostart=false
-Dcoherence.management.report.distributed=false
-Dcoherence.management.report.configuration=reports/report-web-group.xml
-jar coherence.jar

5.2.1 Web Session Storage Report

The Web Session Storage report records statistics on the activity between the cluster and the cache where session objects and data are stored. The statistics include information about the number of put, get, and prune operations performed on the session storage cache, and the amount of time spent on these operations.

The report is a tab-delimited file that is prefixed with the date in YYYYMMDDHH format and appended with -session-storage.txt. For example 2010013113-session-storage.txt would be created on January 31, 2010 1:00 pm. Table 5-5 describes the contents of the Web Session Storage report.

Table 5-5 Contents of the Web Session Storage Report

Column Title

Data Type

Description

Batch Counter

long

A sequential counter to help integrate information between related files. This value resets when the reporter restarts and is not consistent across nodes. However, it is helpful when trying to integrate files.

Cache Name

String

Always session-storage. It is used to maintain consistency with the Cache Utilization report.

Evictions

long

The total number of sessions that have been evicted for the cache across the cluster since the last time the report was created.

Report Time

Date

The system time when the report was created.

Tier

String

The value can be either front or back. Describes whether the cache resides in the front tier (local cache) or back tier (remote cache).

TotalFailures

long

The total number of session storage write failures for the cache across the cluster since the last time the report was created.

TotalGets

long

The total number of session get operations across the cluster since the last time the report was created.

TotalGetsMillis

long

The total number of milliseconds spent for each get() invocation (GetsMillis) to get the sessions across the cluster since the last time the report was created.

TotalHits

long

The total number of session hits across the cluster since the last time the report was created.

TotalHitsMillis

long

The total number of milliseconds spent for each get() invocation that is a hit (HitsMillis) for the session storage across the cluster since the last time the report was created.

TotalMisses

long

The total number of sessions get operations that returned misses for the cache across the cluster since the last time the report was created.

TotalMissesMillis

long

The total number of milliseconds spent for each get() invocation that is a miss (MissesMillis) for the session storage across the cluster since the last time the report was created.

TotalPrunes

long

The total number of times the session storage cache has been pruned across the cluster since the last time the report was created.

TotalPrunesMillis

long

The total number of milliseconds spent for the prune operation (PrunesMillis) to prune the session storage cache across the cluster since the last time the report was created.

TotalPuts

long

The total number of session updates (put operations) across the cluster since the last time the report was created.

TotalPutsMillis

long

The total number of milliseconds spent for each put() invocation (PutsMillis) to update sessions across the cluster since the last time the report was created.

TotalQueue

long

The sum of the queue links for the session storage cache across the cluster.

TotalWrites

long

The total number of sessions written to an external cache storage for the cache across the cluster since the last time the report was created.

TotalWritesMillis

long

The total number of milliseconds spent for each write operation (WritesMillis) to update an external cache storage across the cluster since the last time the report was created.

5.2.2 Web Session Overflow Report

The Web Session Overflow report records statistics on the activity between the cluster and the cache where the overflow of session objects and data is stored. The statistics include information about the number of put, get, and prune operations performed on the session overflow cache, and the amount of time spent on these operations.

The report is a tab-delimited file that is prefixed with the date in YYYYMMDDHH format and appended with -cache-session-overflow.txt. For example 2010013113-cache-session-storage.txt would be created on January 31, 2010 1:00 pm. Table 5-6 describes the contents of the Web Session Overflow report.

Table 5-6 Contents of the Web Session Overflow Report

Column Title

Data Type

Description

Batch Counter

long

A sequential counter to help integrate information between related files. This value does reset when the Reporter restarts and is not consistent across nodes. However, it is helpful when trying to integrate files.

Cache Name

String

Always session-overflow. It is used to maintain consistency with the Cache Utilization report.

Evictions

long

The total number of session overflows that have been evicted for the cache across the cluster since the last time the report was created.

Report Time

Date

The system time when the report executed.

Tier

String

The value can be either front or back. Describes whether the cache resides in the front-tier (local cache) or back tier (remote cache).

TotalFailures

long

The total number of session overflows storage write failures for the cache across the cluster since the last time the report was created.

TotalGets

long

The total number of session overflows get operations across the cluster since the last time the report was created.

TotalGetsMillis

long

The total number of milliseconds spent for each get() invocation (GetsMillis) to get the session overflows across the cluster since the last time the report was created.

TotalHits

long

The total number of session overflow hits across the cluster since the last time the report was created.

TotalHitsMillis

long

The total number of milliseconds spent for each get() invocation that is a hit (HitsMillis) for the session overflow across the cluster since the last time the report was created.

TotalMisses

long

The total number of session overflow get operations that returned misses for the cache across the cluster since the last time the report was created.

TotalMissesMillis

long

The total number of milliseconds spent for each get() invocation that is a miss (MissesMillis) for the session overflow across the cluster since the last time the report was created.

TotalPrunes

long

The total number of times the session overflow cache has been pruned across the cluster since the last time the report was created.

TotalPrunesMillis

long

The total number of milliseconds spent for the prune operations (PrunesMillis) to prune the session overflow cache across the cluster since the last time the report was created.

TotalPuts

long

The total number of session overflows (put operations) across the cluster since the last time the report was created.

TotalPutsMillis

long

The total number of milliseconds spent per put() invocation (PutsMillis) to update session overflows across the cluster since the last time the report was created.

TotalQueue

long

The sum of the queue link size for the session overflow cache across the cluster.

TotalWrites

long

The total number of session overflows written to an external cache storage for the cache across the cluster since the last time the report was created.

TotalWritesMillis

long

The total number of milliseconds spent for each write operation (WritesMillis) to update an external session overflow storage across the cluster since the last time the report was created.

5.2.3 Web Report

The Web Report (report-web.xml) provides information about Coherence*Web activity for the cluster. The report is a tab-delimited file that is prefixed with the date and hour in YYYYMMDDHH format and appended with -web.txt. For example 2009013102-web.txt would be created on January 1, 2009 at 2:00 am. Table 5-7 describes the contents of the Web Report.

Table 5-7 Contents of the Web Report

Column

Data Type

Description

Application

String

The application name.

Batch Counter

long

A sequential counter to help integrate information between related files. This value does reset when the Reporter restarts and is not consistent across nodes. However, it is helpful when trying to integrate files.

Current Overflow Updates

long

The number of overflow updates since the last time the report was created.

Current Session Updates

long

The number of session updates since the last time the report was created.

LocalAttributeCount

long

The attribute count on the node.

LocalSessionCount

long

The session count on the node.

Node Id

integer

The node identifier.

OverflowAvgSize

float

The average size for attribute overflows.

OverflowMaxSize

long

The maximum size for an attribute overflow.

OverflowUpdates

long

The total number of attribute overflow updates since the last time statistics were reset.

Report Time

Date

The system time when the report was created.

SessionAverageLifetime

float

The average number of seconds a session is active.

SessionAverageSize

float

The average size for a session.

SessionMaxSize

long

The maximum size for a session.

SessionMinSize

long

The minimum size for a session.

SessionStickyCount

long

The number of sticky sessions on the node.

SessionUpdateCount

long

The number of session updates since the last time statistics were reset.

5.2.4 WebLogic Web Report

The Weblogic Web Report (report-web-weblogic.xml) provides information on Coherence*Web activity when it is being used in WebLogic Server environments. This report provides the same information as provided by the Web Report (see "Web Report", above), with additional columns for the WebLogic Server name and domain name. The report is a tab-delimited file that is prefixed with the date and hour in YYYYMMDDHH format and appended with -web-weblogic.txt. For example 2009013102-web-weblogic.txt would be created on January 1, 2009 at 2:00 am.

Table 5-8 Contents of the WebLogic Web Report

Column

Data Type

Description

Application

String

The application name.

Batch Counter

long

A sequential counter to help integrate information between related files. This value does reset when the Reporter restarts and is not consistent across nodes. However, it is helpful when trying to integrate files.

Current Overflow Updates

long

The number of overflow updates since the last time the report was created.

Current Session Updates

long

The number of session updates since the last time the report was created.

DomainName

String

The name of the WebLogic Server domain in which Coherence*Web is running.

LocalAttributeCount

long

The attribute count on the node.

LocalSessionCount

long

The session count on the node.

Node Id

integer

The node identifier.

OverflowAvgSize

float

The average size for attribute overflows.

OverflowMaxSize

long

The maximum size for an attribute overflow.

OverflowUpdates

long

The total number of attribute overflow updates since the last time statistics were reset.

Report Time

Date

The system time when the report was created.

ServerName

String

The name of the WebLogic Server on which Coherence*Web is running.

SessionAverageLifetime

float

The average number of seconds a session is active.

SessionAverageSize

float

The average size for a session.

SessionMaxSize

long

The maximum size for a session.

SessionMinSize

long

The minimum size for a session.

SessionStickyCount

long

The number of sticky sessions on the node.

SessionUpdateCount

long

The number of session updates since the last time statistics were reset.

5.2.5 Web Service Report

The Web Service report provides information about the service running the Coherence*Web application. The report records the requests processed, request failures, and request backlog, tasks processed, task failures, and task backlog. Request Count and Task Count are useful to determine performance and throughput of the service. RequestPendingCount and Task Backlog are useful in determining capacity issues or blocked processes. Task Hung Count, Task Timeout Count, Thread Abandoned Count, Request Timeout Count are the number of unsuccessful executions that have occurred in the system.

The report is a tab-delimited file that is prefixed with the date and hour in YYYYMMDDHH format and appended with -web-session-service.txt. For example 2009013102-web-session-service.txt would be created on January 1, 2009 at 2:00 am. Table 5-9 describes the contents of the Web Service Report.

Table 5-9 Contents of the Web Service Report

Column Title

Data Type

Description

Batch Counter

Long

A sequential counter to help integrate information between related files. This value does reset when the Reporter restarts and is not consistent across nodes. However, it is helpful when trying to integrate files.

Node Id

String

The numeric node identifier.

Refresh Time

Date

The system time when the service information was updated from a remote node.

Request Count

Long

The number of requests by the Coherence*Web application since the last report was created.

RequestPendingCount

Long

The number of pending requests by the Coherence*Web application at the time of the report.

RequestPendingDuration

Long

The duration for the pending requests of the Coherence*Web application at the time of the report.

Request Timeout Count

Long

The number of request timeouts by the Coherence*Web application since the last report was created.

Report Time

Date

The system time when the report executed.

Service

String

A static value (DistributedSessions) used as the service name if merging the information with the service file.

Task Backlog

Long

The task backlog of the Coherence*Web application at the time of the report was created.

Task Count

Long

The number of tasks executed by the Coherence*Web application since the last report was created.

Task Hung Count

Long

The number of tasks that were hung by the Coherence*Web application since the last report was created.

Task Timeout Count

Long

The number of task timeouts by the Coherence*Web application since the last report was created.

Thread Abandoned Count

Long

The number of threads abandoned by the Coherence*Web application since the last report was created.

6 Cleaning Up Expired HTTP Sessions

This chapter describes how to configure and use the Session Reaper. The Session Reaper is responsible for destroying any session that is no longer used, which is determined by when that session has timed out.

This chapter contains the following sections:

- Understanding the Session Reaper

- Tuning the Session Reaper

- Getting Session Reaper Performance Statistics

- Understanding Session Invalidation Exceptions for the Session Reaper

As part of Coherence*Web Session Management Module, HTTP sessions that have expired are eventually cleaned up by the Session Reaper. The Session Reaper provides a service similar to the JVM Garbage Collection (GC) capability: the Session Reaper is responsible for destroying any session that is no longer used, which is determined by when that session has timed out.

Each HTTP session contains two pieces of information that determine when it has timed out. The first is the LastAccessedTime property of the session, which is the time stamp of the most recent activity involving the session. The second is the MaxInactiveInterval property of the session, which specifies how long the session is kept active without any activity; a typical value for this property is 30 minutes. The MaxInactiveInterval property defaults to the value configured for Coherence*Web, but it can be modified on a session-by-session basis.

Each time that an HTTP request is received by the server, if there is an HTTP session associated with that request, then the LastAccessedTime property of the session is automatically updated to the current time. As long as requests continue to arrive related to that session, it is kept active, but when a period of inactivity occurs longer than that specified by the MaxInactiveInterval property, then the session expires. Session expiration is passive—occurring only due to the passing of time. The Coherence*Web Session Reaper scans for sessions that have expired, and when it finds expired sessions it destroys them.

6.1 Understanding the Session Reaper

The Session Reaper configuration addresses three basic questions:

- On which servers will the Reaper run?

- How frequently will the Reaper run?

- When the Reaper runs, on which servers will it look for expired sessions?

Understanding Where the Session Reaper Runs

Every application server running Coherence*Web runs the Session Reaper. That means that if Coherence is configured to provide a separate cache tier (made up of cache servers), then the Session Reaper does not run on those cache servers.

By default, the Session Reaper runs concurrently on all of the application servers, so that all of the servers share the workload of identifying and cleaning up expired sessions. The coherence-reaperdaemon-cluster-coordinated context parameter causes the cluster to coordinate reaping so that only one server at a time performs the actual reaping; the use of this option is not suggested, and it cannot be used with the Coherence*Web over Coherence*Extend topology.

The coherence-reaperdaemon-cluster-coordinated context parameter should not be used if sticky optimization (coherence-sticky-sessions) is also enabled. Because only one server at a time performs the reaping, sessions owned by other nodes cannot be reaped. This means that it will take longer for sessions to be reaped as more nodes are added to the cluster. Also, the reaping ownership does not circulate over the nodes in the cluster in a controlled way; one node can be the reaping node for a long time before it is taken over by another node. During this time, only its own sessions are reaped.

Understanding How Frequently the Session Reaper Runs

The Session Reaper is configured to scan the entire set of sessions over a certain period, called a reaping cycle, which defaults to five minutes. This length of the reaping cycle is specified by the coherence-reaperdaemon-cycle-seconds context parameter. This setting indicates to the Session Reaper how aggressively it must work. If the cycle length is configured too short, the Session Reaper uses additional resources without providing additional benefit. If the cycle length is configured too long, then expired sessions will use heap space in the Coherence caches unnecessarily. In most situations, it is far preferable to reduce resource usage than to ensure that sessions are cleaned up quickly after they expire. Consequently, the default cycle of five minutes is a good balance between promptness of cleanup and minimal resource usage.

During the reaping cycle, the Session Reaper scans for expired sessions. In most cases, the Session Reaper takes responsibility for scanning all of the HTTP sessions across the entire cluster, but there is an optimization available for the single tier topology. In the single tier topology, when all of the sessions are being managed by storage-enabled Coherence cluster members that are also running the application server, the session storage is colocated with the application server. Consequently, it is possible for the Session Reaper on each application server to scan only the sessions that are stored locally. This behavior can be enabled by setting the coherence-reaperdaemon-assume-locality configuration option to true.

Regardless of whether the Session Reaper scans only colocated sessions or all sessions, it does so in a very efficient manner by using these advanced capabilities of the Coherence data grid:

- The Session Reaper delegates the search for expired sessions to the data grid using a custom ValueExtractor implementation. This ValueExtractor takes advantage of the BinaryEntry interface so that it can determine if the session has expired without even deserializing the session. As a result, the selection of expired sessions can be delegated to the data grid just like any other parallel query, and can be executed by storage-enabled Coherence members in a very efficient manner.

- The Session Reaper uses the com.tangosol.net.partition.PartitionedIterator class to automatically query on a member-by-member basis, and in a random order that avoids harmonics in large-scale clusters.

Each storage-enabled member can very efficiently scan for any expired sessions, and it has to scan only one time per application server per reaper cycle. The result is a default Session Reaper configuration that works well for application server clusters with one or multiple servers.

Understanding How the Session Reaper Runs

Coherence*Web uses a work manager to retrieve threads to execute the parallel reaping. WebLogic Server defines a default work manager, wm/CoherenceWorkManager, which it will attempt to use. If no work manager is defined with that name, it will use the default work manager implemented in Coherence.

To ensure that the Session Reaper does not impact the smooth operation of the application server, it breaks up its work into chunks and schedules that work in a manner that spreads the work across the entire reaping cycle. Because the Session Reaper has to know how much work it must schedule, it maintains statistics on the amount of work that it performed in previous cycles, and uses statistical weighting to ensure that statistics from recent reaping cycles count more heavily. There are several reasons why the Session Reaper breaks up the work in this manner:

- If the Session Reaper consumed a large number of CPU cycles simultaneously, it could cause the application to be less responsive to users. By doing a small portion of the work at a time, the application remains responsive.

- One of the key performance enablers for Coherence*Web is the near-caching feature of Coherence; because the sessions that are expired are accessed through that same near cache to clean them, expiring too many sessions too quickly could cause the cache to evict sessions that are being used on that application server, leading to performance loss.

The Session Reaper performs its job efficiently, even with the default configuration by:

- Delegating as much work as possible to the data grid

- Delegating work to only one member at a time

- Enabling the data grid to find expired sessions without deserializing them

- Restricting the usage of CPU cycles

- Avoiding cache-thrashing of the near caches that Coherence*Web relies on for performance

Understanding How the Session Reaper Removes Sessions

The Session Reaper can invalidate sessions either in parallel or serially. By default, it invalidates sessions in parallel. This ensures that sessions are invalidated in a timely manner. However, if the application server JVM has a high system load due to a large number of concurrent threads, then you have the option of invalidating serially. To configure the reaper to invalidate sessions serially, set the coherence-reaperdaemon-parallel context parameter to false.

The Session Reaper deletes sessions that have timed-out. The default behavior is to remove the session after fetching it from the local JVM and calling the invalidate method on the HTTP session. However, the session reaper can also be configured to delete sessions remotely using a Coherence entry processor. In this case, the invalidate method of the HTTP session and the session listeners are not invoked. Deleting sessions remotely is much faster than the default mechanism but should only be used in applications that do not use session listeners. To configure the reaper to delete sessions remotely, set the coherence-session-reaping-mechanism context parameter to RemoteDelete.

6.2 Tuning the Session Reaper

The following are suggestions for tuning the default Session Reaper configuration:

- If the application is deployed with the in-process topology, then set the coherence-reaperdaemon-assume-locality configuration option to true.

- Because all of the application servers are responsible for scanning for expired sessions, it is reasonable to increase the coherence-reaperdaemon-cycle-seconds configuration option if the cluster is larger than 10 application servers. The larger the number of application servers, the longer the cycle can be; for example, with 200 servers, it would be reasonable to set the length of the reaper cycle as high as 30 minutes (that is, setting the coherence-reaperdaemon-cycle-seconds configuration option to 1800).

- If the application does not use session listeners, then set the coherence-session-reaping-mechanism context parameter to RemoteDelete.

6.3 Getting Session Reaper Performance Statistics

The HttpSessionManagerMBeanWeb provides several attributes that serve as performance statistics for the Session Reaper. These statistics, described in the following list, include the average time duration for a reap cycle, the number of sessions reaped, and the time until the next reap cycle:

- AverageReapDuration, which is the average reap duration (the time it takes to complete a reap cycle), in milliseconds, since the statistic was reset

- LastReapDuration, which is the time in milliseconds it took for the last reap cycle to finish

- MaxReapedSessions, which is the maximum number of sessions reaped in a reap cycle since the statistic was reset

- NextReapCycle, which is the time (as a java.lang.Date data type) for the next reap cycle

- ReapedSessions, which is the number of sessions reaped during the last cycle

- ReapedSessionsTotal, which is the number of expired sessions that have been reaped since the statistic was reset

These attributes are also described in Table 5-2 in the section "Managing and Monitoring Applications with JMX".

You can access these attributes in a monitoring tool such as JConsole. However, you must set up the Coherence Clustered JMX Framework before you can access them. The configuration and installation instructions for the framework is provided in "Using JMX to Manage Coherence" in Managing Oracle Coherence.

6.4 Understanding Session Invalidation Exceptions for the Session Reaper

Each Coherence*Web instance has a Session Reaper that will periodically iterate through all of the sessions in the session cache and check for expired sessions. If multiple Web applications are using Coherence*Web, then a reaper from one Web application can invalidate sessions used in a different application. Session listeners registered with the Web application that is reaping expired sessions will be executed.

Session attribute listeners will attempt to retrieve the session attribute values during invalidation. If the session attributes are dependent on classes that exist only in the original Web application, then a class not found exception will be thrown and logged in the Session Reaper. These exceptions will not cause any disruption in the Web application or the application server.

Coherence*Web provides a context parameter, coherence-session-log-invalidation-exceptions, to control whether these exceptions are logged. The default value, true, allows the exceptions to be logged. If you want to suppress the logging of these exceptions, set this context parameter to false.

7 Working with JSF and MyFaces Applications

This chapter describes how to configure Coherence*Web for JavaServer Faces (JSF) and MyFaces applications. JSF is a framework that enables you to build user interfaces for Web applications. MyFaces, from the Apache Software Foundation, provides JSF components that extend the JSF specification. MyFaces components are completely compatible with the JSF 1.1 Reference Implementation or any other compatible implementation.

This chapter contains the following sections:

- Configuring for all JSF and MyFaces Web Applications:

- Configuring for Instrumented Applications that use MyFaces

- Configuring for Instrumented Applications that use Mojarra

7.1 Configuring for all JSF and MyFaces Web Applications:

JSF and MyFaces attempts to cache the state of the view in the session object. This state data should be serializable by default, but there could be situations where this would not be the case. For example:

- If Coherence*Web reports IllegalStateException due to a non-serializable class, and all the attributes placed in the session by your Web-application are serializable, then you must configure JSF/MyFaces to store the state of the view in a hidden field on the rendered page.

- If the Web application puts non-serializable objects in the session object, you must set the coherence-preserve-attributes context parameter to true.

The JSF parameter javax.faces.STATE_SAVING_METHOD identifies where the state of the view is stored between requests. By default, the state is saved in the servlet session. Set the STATE_SAVING_METHOD parameter to client in the context-param stanza of the web.xml file, so that JSF stores the state of the entire view in a hidden field on the rendered page. If you do not, then JSF may attempt to cache that state, which is not serializable, in the session object.

Example 7-1 illustrates setting the STATE_SAVING_METHOD parameter in the web.xml file.

Example 7-1 Setting STATE_SAVING_METHOD in the web.xml File

...
<context-param>
<param-name>javax.faces.STATE_SAVING_METHOD</param-name>
<param-value>client</param-value>
</context-param>
...

7.2 Configuring for Instrumented Applications that use MyFaces

If you are deploying the MyFaces application with the Coherence*Web WebInstaller (that is, an instrumented application), then you might have to complete an additional step based on the version of MyFaces.

- If you are using Coherence*Web WebInstaller to deploy a Web-application built with a pre-1.1.n version of MyFaces, then nothing more needs to be done.

- If you are using Coherence*Web WebInstaller to deploy a Web-application built with a 1.2.x version of MyFaces, then add the context parameter org.apache.myfaces.DELEGATE_FACES_SERVLET to the web.xml file. This parameter allows you to specify a custom servlet instead of the default javax.faces.webapp.FacesServlet.
Example 7-2 illustrates setting the DELEGATE_FACES_SERVLET context parameter in the web.xml file.

Example 7-2 Setting DELEGATE_FACES_SERVLET in the web.xml File

...
<context-param>
<param-name>org.apache.myfaces.DELEGATE_FACES_SERVLET</param-name>
<param-value>com.tangosol.coherence.servlet.api23.ServletWrapper</param-value>
</context-param>
...

7.3 Configuring for Instrumented Applications that use Mojarra

If you are using Coherence*Web WebInstaller to deploy a Web application based on the JSF Reference Implementation (Mojarra), then you must declare the FacesServlet class in the servlet stanza of the web.xml file.

Example 7-3 Declaring the Faces Servlet in the web.xml File

...
<servlet>
<servlet-name>Faces Servlet (for loading config)</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
</servlet>
...

A Coherence*Web Context Parameters

This appendix describes the Coherence*Web context parameters. Coherence*Web configuration parametersconfiguration parametersThe parameters can be configured in the web.xml file or they can also be entered on the command line as system properties. The system properties have the same name as the context parameters, but the dash (-) is replaced with a period (.).

For example, the context parameter coherence-enable-sessioncontext can be declared on the command line by:

-Dcoherence.enable.sessioncontext=true

If both a system property and the equivalent context parameter are configured, the value from the system property is honored.

Table A-1 describes the context parameters for Coherence*Web.

Table A-1 Context Parameters for Coherence*Web

Parameter Name

Description

coherence-application-name

Coherence*Web uses the value of this parameter to determine the name of the application that uses the ApplicationScopeController interface to scope attributes. The value for this parameter should be provided in the following format:

application name + ! + Web module name

The application name is the name of the application that uses the ApplicationScopeController interface and Web module name is the name of the Web module in which it appears.

For example, if you have an EAR file named test.ear and a Web-module named app1 defined in the EAR file, then the default value for the coherence-application-name parameter would be test!app1.

If this parameter is not configured, then Coherence*Web uses the name of the class loader instead. Also, if the parameter is not configured and the ApplicationScopeController interface is configured, then a warning is logged saying that the application name was not configured. See "Session Attribute Scoping" for more information.

coherence-attribute-overflow-threshold

For the Split Model, described in "Session Models", this value specifies the minimum length (in bytes) that the serialized form of an attribute value must be for it to be stored in the separate overflow cache that is reserved for large attributes.

If unspecified, this parameter defaults to 1024.

coherence-cache-configuration-path

Specifies the name of the file that Coherence*Web should use to obtain session cache information, instead of using the default default-session-cache-config.xml file. See "Customizing the Name of the Session Cache Configuration File".

coherence-cache-delegator-class

Specifies a cache delegator class that is responsible for manipulating (getting, putting, or deleting) data in the distributed cache. Valid value is:

- com.tangosol.coherence.servlet.LocalSessionCacheDelegator—This class indicates that the local cache should be used for storing and retrieving the session instance before attempting to use the distributed cache. See "Getting Concurrent Access to the Same Session Instance" for more information.

coherence-cluster-owned

If true, Coherence*Web automatically shuts down the Coherence node when the Web application shuts down. You must use the WAR-scoped cluster node deployment model in this case. See "WAR-Scoped Cluster Nodes" for more information.

If false, the Web application is responsible for shutting down the Coherence node (see com.tangosol.net.CacheFactory.shutdown()in the Javadoc). You must carefully consider a cluster node-scoping deployment model in this case and the circumstances under which the application shuts down the Coherence node and the side effects of doing so. See "Cluster Node Isolation" for more information on cluster node scoping.

Note: When using the WebInstaller, a value of true instructs the WebInstaller to place the Coherence library in the WEB-INF/lib directory of each Web application found in your Java EE application.

If unspecified, this parameter defaults to false.

coherence-configuration-consistency

If true, Coherence*Web runs a configuration check at startup to determine whether all nodes in the Web tier have the same Coherence*Web configuration. If the configuration of a particular node is not consistent, then it will fail to start (which, in turn, prevents the application from starting).

If false, (there is no checking) and the configurations are not consistent, then the cluster members might exhibit inconsistent behavior in managing the session data.

If unspecified, this parameter defaults to false.

coherence-contextless-session-retain-millis

Specifies the number of milliseconds that a server holds a lock on a session while accessing it without the session being implied by the current request context. A session is implied by the current request context if and only if the current thread is processing a servlet request, and the request is associated with that session. All other access to a session object is out of context. For example, if a reference to an arbitrary session is obtained from a SessionContext object (if that option is enabled), or if the application has code that holds on to session object references to manage sessions directly. Because session access requires session ownership, out of context access to the session object automatically obtains ownership on behalf of the caller; that ownership will be retained for the number of milliseconds specified by this option so that repeated calls to the session do not individually obtain and release ownership, which is potentially an expensive operation. The valid range is 10 to 10000 (from 1/100th of a second up to 10 seconds).

If unspecified, this parameter defaults to 200.

coherence-distributioncontroller-class

This value specifies a class name of the com.tangosol.coherence.servlet.HttpSessionCollection$SessionDistributionController interface implementation.

Valid values include:

- com.tangosol.coherence.servlet.AbstractHttpSessionCollection$DistributedController an implementation of the SessionDistributionController interface that forces all sessions (and thus their attributes) to be managed in a distributed manner. This is the default behavior, but by having an implementation that forces this, the raw overhead of using a HttpSessionController can be measured.

- com.tangosol.coherence.servlet.AbstractHttpSessionCollection$HybridController an implementation of the SessionDistributionController interface that forces all sessions and serializable attributes to be managed in a distributed manner. All session attributes that do not implement the Serializable interface will be kept local.

- com.tangosol.coherence.servlet.AbstractHttpSessionCollection$LocalController an implementation of the SessionDistributionController interface that forces all sessions (and thus their attributes) to be managed locally. This might not be useful for production purposes, but it can be useful for testing the difference in scalable performance between local-only and fully-distributed implementations.

coherence-enable-sessioncontext

When set to true, this parameter allows the application to iterate sessions from the session context, thus disobeying the deprecation in the servlet specification.

If unspecified, this parameter defaults to false.

coherence-eventlisteners

This is the comma-delimited list of names of application classes that want to receive events from the Web container. This list comes from the application listeners declared in the listener elements of the web.xml file.

coherence-enable-suspect-attributes

If set to true, Coherence*Web attempts to detect whether the value of any session-related attributes have changed. Attributes that can be changed (determined with a simple check) and that can be accessed by a get method are deemed to be suspect. Changeable objects might have been changed by application code and must be re-serialized back into the cache. See "Detecting Changed Attribute Values" for more information.

If unspecified, this parameter defaults to true.

coherence-factory-class

This is the fully qualified name of the class that implements the SessionHelper.Factory factory class.

This parameter defaults to com.tangosol.coherence.servlet.apinn.DefaultFactory where nn is 22, 23, 24, or 25 for Servlet 2.2, 2.3, 2.4, or 2.5 containers respectively.

coherence-local-session-cachename

This name overrides the name of the local cache that stores nondistributed sessions when the coherence-distributioncontroller-class parameter is specified.

If unspecified, this parameter defaults to local-session-storage. Session Cache Configuration File describes this parameter.

coherence-local-attribute-cachename

This name overrides the name of the local cache that stores non-distributed sessions when either the coherence-sessiondistributioncontroller-class parameter is specified or the coherence-preserve-attributes parameter is true.

If unspecified, this parameter defaults to local-attribute-storage. Session Cache Configuration File describes this parameter.

coherence-preserve-attributes

This value, if set to true, specifies that non-serializable attributes should be preserved as local ones. This parameter requires a load balancer to be present to retrieve non-serializable attributes for a session.

These attributes will be lost if the client (application server) fails. The application would need to be able to recover from this.

If unspecified, this parameter defaults to false.

coherence-reaperdaemon-assume-locality

This setting allows the Session Reaper to assume that the sessions that are stored on this node (for example, by a distributed cache service) are the only sessions that this node must check for expiration. This value must be set to false if the session storage cache is being managed by nodes that are not running a reaper, for example if cache servers are being used to manage the session storage cache.

If cache servers are being used, select the Split Model and run the session overflow storage in a separate distributed cache service that is managed entirely by the cache servers. Leave the session storage cache itself in a distributed cache service that is managed entirely by the application server JVMs so they can take advantage of this assume locality feature. See Cleaning Up Expired HTTP Sessions for more information about the Session Reaper.

If unspecified, this parameter defaults to true.

coherence-reaperdaemon-cluster-coordinated

If true, the Session Reaper coordinates reaping in the cluster such that only one server will perform reaping within a given reaping cycle, and it will be responsible for checking all of the sessions that are being managed in the cluster. See Cleaning Up Expired HTTP Sessions for more information about the Session Reaper.

This option should not be used if sticky optimization (coherence-sticky-sessions) is also enabled. See "Understanding the Session Reaper" for more information.

If unspecified, this parameter defaults to false.

coherence-reaperdaemon-cycle-seconds

This is the number of seconds that the daemon rests between reaping. For production clusters with long session timeout intervals, this can safely be set higher. For testing, particularly with short session timeout intervals, it can be set much lower. Setting it too low can cause more network traffic and use more processing cycles, and has benefit only if the application requires the sessions to be invalidated quickly when they have expired. See Cleaning Up Expired HTTP Sessions for more information about the Session Reaper.

If unspecified, this parameter defaults to 300.

coherence-reaperdaemon-parallel

If set to true, the Session Reaper will invalidate expired sessions in parallel. When set to false, expired sessions will be invalidated serially. See "Understanding the Session Reaper".

The default is true.

coherence-reaperdaemon-priority

This is the priority for the Session Reaper daemon. For more information, see Cleaning Up Expired HTTP Sessions and the source for the java.lang.Thread class.

If unspecified, this parameter defaults to 5.

coherence-session-reaping-mechanism

This property indicates the mechanism that is used by the session reaper to delete timed-out sessions. Valid values are Default and RemoteDelete. For more information, see Cleaning Up Expired HTTP Sessions.

The default is Default

coherence-scopecontroller-class

This value specifies a class name of the optional com.tangosol.coherence.servlet.HttpSessionCollection$AttributeScopeController interface implementation. See "Session Attribute Scoping" for more information.

Valid values include:

- com.tangosol.coherence.servlet.AbstractHttpSessionCollection$ApplicationScopeController

- com.tangosol.coherence.servlet.AbstractHttpSessionCollection$GlobalScopeController

The default value for Coherence*Web is com.tangosol.coherence.servlet.AbstractHttpSessionCollection$ApplicationScopeController

For Coherence*Web WebInstaller, there is no declared default value.

coherence-servletcontext-clustered

This value is either true or false to indicate whether the attributes of the ServletContext will be clustered. If true, then all serializable ServletContext attribute values will be shared among all cluster nodes.

If unspecified, this parameter defaults to false, primarily because the servlet specification indicates that the ServletContext attributes are local to a JVM and should not be clustered.

coherence-servletcontext-cachename

This specifies the name of the Coherence cache to be used to hold the servlet context data if the servlet context is clustered.

If unspecified, this parameter defaults to servletcontext-storage. Session Cache Configuration File describes this parameter.

coherence-session-affinity-token

Configures the session affinity suffix token with a given value. For example, to set the session affinity suffix to abcd, add the following code to the Web application's web.xml file:

<context-param>
<param-name>coherence-session-affinity-token</param-name>
<param-value>abcd</param-value>
</context-param>

To strip the session affinity suffix from the token, enter an exclamation point (!) as the parameter value. See "Sharing Coherence*Web Sessions with Other Application Servers" for more information.

coherence-session-app-locking

This value, if set to true, will prevent two threads in different applications from processing a request for the same session at the same time. If set to true the value of the coherence-session-member-locking parameter will be ignored, because application locking implies member locking. A value of false is incompatible with thread locking.

If unspecified, this parameter defaults to false.

See also coherence-session-member-locking, coherence-session-locking, and coherence-session-thread-locking parameter descriptions in this table and "Session Locking Modes".

coherence-session-cachename

This name overrides the name of the clustered cache that stores the sessions.

If unspecified, this parameter defaults to session-storage. Session Cache Configuration File describes this parameter.

coherence-session-cache-federated

This specifies whether the session cache is federated among cluster participants. Valid values are true and false. If set to true, the default-federated-session-cache-config.xml session cache configuration file is used and results in the session cache being federated. For details, see "Federated Session Caches."

The default is false

coherence-session-cookie-domain

This specifies the domain of the session cookie as defined by Request for Comments 2109: HTTP State Management Mechanism (RFC 2109). By default, no domain is set explicitly by the session management implementation. See "Session and Session Attribute Scoping" for more information.

coherence-session-cookie-httponly

Appends the HttpOnly attribute to the session cookie. Note that not all browsers support this functionality. This context parameter can be used only with instrumented applications. See "Preventing Cross-Site Scripting Attacks" for more information.

coherence-session-cookie-name

This specifies the name of the session cookie.

If unspecified, this parameter defaults to JSESSIONID.

coherence-session-cookie-path

This specifies the path of the session cookie as defined by RFC 2109. By default, no path is set explicitly by the session management implementation. See "Session and Session Attribute Scoping" for more information.

coherence-session-cookie-max-age

This specifies the maximum age in seconds of the session cookie as defined by RFC 2109. A value of -1 indicates that the cookie will not persist on the client; a positive value gives the maximum age that the cookie will be persistent for the client. Zero is not permitted.

If unspecified, this parameter defaults to -1.

coherence-session-cookie-secure

If true, this value ensures that the session cookie will be sent only from a Web client over a Secure Socket Layer (SSL) connection. If unspecified, the default is false.

coherence-session-cookies-enabled

If unspecified, this parameter defaults to true to enable session cookies.

coherence-session-expire-seconds

This value overrides the session expiration time, and is expressed in seconds. Setting it to -1 causes sessions to never expire. See Cleaning Up Expired HTTP Sessions for more information.

If unspecified, this parameter defaults to 1800.

coherence-session-get-lock-timeout

This value configures a timeout for lock acquisition for Coherence*Web. See "Troubleshooting Locking in HTTP Sessions" for more information.

coherence-session-id-length

This is the length, in characters, of generated session IDs. The suggested absolute minimum length is 8.

If unspecified, this parameter defaults to 12.

coherence-session-lazy-access

This value enables lazy acquisition of sessions. A session will be acquired only when the servlet or filter attempts to access it. This is relevant only for instrumented Web applications. See "Accessing Sessions with Lazy Acquisition".

If unspecified, this parameter defaults to false.

coherence-session-locking

If false, concurrent modification to sessions, with the last update being saved, will be allowed. If coherence-session-app-locking, coherence-session-member-locking, or coherence-session-thread-locking are set to true, then this value is ignored (being logically true). See "Optimistic Locking" and "Last-Write-Wins Locking".

If unspecified, this parameter defaults to false.

See also coherence-session-app-locking, coherence-session-member-locking, and coherence-session-thread-locking in this table.

coherence-session-locking-mode

The value of this context parameter determines the locking mode that will govern concurrent access to HTTP sessions.

- none—This value allows concurrent access to a session by multiple threads in a single member or multiple members. In this case, the last write is saved. This is the default locking mode. See "Last-Write-Wins Locking".

- optimistic—This value allows multiple web container threads in one or more members to access the same session concurrently. See "Optimistic Locking".

- app—This value prevent two threads in different applications from processing a request for the same session at the same time. If this parameter is set to app, then the value of the coherence-session-member-locking parameter will be ignored, because application locking implies member locking. A value of false is incompatible with thread locking. See "Application Locking".

- member—This value allows multiple web container threads in the same cluster node to access and modify the same session concurrently, but prohibits concurrent access by threads in different members. See "Member Locking".

- thread—This value prevents two threads in the same JVM from processing a request for the same session at the same time. If set to true, the value of the coherence-session-member-locking parameter is ignored, because thread locking implies member locking. See "Thread Locking".

For example, to set the coherence-session-locking-mode context parameter to application locking in web.xml:

<context-param>
<param-name>coherence-session-locking-mode</param-name>
<param-value>app</param-value>
</context-param>

coherence-session-log-invalidation-exceptions

During session invalidation, many class not found exceptions might be thrown and logged in the session reaper. If this context parameter is set to false, then the exceptions will be suppressed. If set to true, then the exceptions will be logged.

If unspecified, this parameter defaults to true.

For more information on session invalidation and the cause of the class not found exceptions that might occur during operation of the session reaper, see "Understanding Session Invalidation Exceptions for the Session Reaper".

coherence-session-log-threads-holding-lock

If true, this value specifies if a diagnostic invocation service is executed when a member cannot acquire the cluster lock for a session. The invocation service will cause the member that has ownership of the session to log the stack trace of the threads that are currently holding the lock. The coherence-session-log-threads-holding-lock context parameter is available only when the coherence-sticky-sessions context parameter is set to true.

If unspecified, this parameter defaults to true.

See "Troubleshooting Locking in HTTP Sessions" for more information.

coherence-session-logger-level

An alternative way to set the logging level for Coherence*Web (as opposed to JDK logging). The valid values for this parameter are the same as for JDK logging: SEVERE, WARNING, INFO, CONFIG, FINE, FINER (default), and FINEST. See "Configuring Logging for Coherence*Web" for more information.

See also the Javadoc for java.util.logging:

http://docs.oracle.com/javase/1.4.2/docs/api/java/util/logging/Level.html

coherence-session-management-cachename

This name overrides the name of the clustered cache that stores the management and configuration information for the session management implementation. Generally, it should be configured as a replicated cache.

If unspecified, this parameter defaults to session-management. Session Cache Configuration File describes this parameter.

coherence-session-member-locking

If true, this value prevents two threads in different members from processing a request for the same session at the same time.

If unspecified, this parameter defaults to false.

See also coherence-session-thread-locking, coherence-session-locking, and coherence-session-app-locking in this table.

coherence.session.optimizeModifiedSessions

This JVM system property, if set to true, enables near cache optimizations which can improve performance with applications that use Last-Write-Wins locking.

If unspecified, this value defaults to false.

This parameter can be set only on the command line as a system property.

coherence-session-overflow-cachename

For the Split Model, this value overrides the name of the clustered cache that stores the large attributes that exceed a certain size and thus are determined to be more efficiently managed as separate cache entries and not as part of the serialized session object itself.

If unspecified, this parameter defaults to session-overflow. Session Cache Configuration File describes this parameter.

coherence-session-strict-spec

If false, then the implementation will not be required to adhere to the servlet specification. The implementation will ignore certain types of exceptions and the application will not terminate. Setting, getting, and removing attributes, or invalidating sessions will not generate any callbacks to session listeners. Any ClassNotFound exceptions will not be propagated back to the caller if an attribute cannot be deserialized because the class does not exist in the invoking application.

If true, then the implementation strictly adheres to the servlet specification. ClassNotFound exceptions must be handled by the application, and session listener events will be sent, even if retrieving the attribute value fails.

If unspecified, this parameter defaults to true.

coherence-session-thread-locking

If true, this value prevents two threads in the same JVM from processing a request for the same session at the same time. If set to true, the value of the coherence-session-member-locking parameter is ignored, because thread locking implies member locking.

If unspecified, this parameter defaults to false.

See also coherence-session-app-locking, coherence-session-locking, and coherence-session-member-locking parameter descriptions in this table and "Session Locking Modes".

coherence-session-urldecode-bycontainer

If true, this value uses the container's decoding of the URL session ID. If coherence-session-urlencode-name has been overridden, this must be set to false. Setting this to false will not work in some containers.

If unspecified, this parameter defaults to true.

coherence-session-urlencode-bycontainer

If true, this value uses the container's encoding of the URL session ID. Setting this to true could conflict with the setting for coherence-session-urlencode-name if it has been specified.

If unspecified, this parameter defaults to false.

coherence-session-urlencode-enabled

If true, this value enables URL encoding of session IDs.

If unspecified, this parameter defaults to true.

coherence-session-urlencode-name

This is the parameter name to encode the session ID into the URL. On some containers, this value cannot be overridden.

If unspecified, this parameter defaults to jsessionid.

coherence-session-weblogic-compatibility-mode

If true, a single session ID (with the cookie path set to "/") will map to a unique Coherence*Web session instance in each Web application. If false, then the standard behavior will apply: that is, a single session ID will map to a single session instance. All other session persistence mechanisms in WebLogic Server use a single session ID in each Web application to refer to different session instances.

If unspecified, this parameter defaults to true. An exception is when the application is configured to use the global scope controller. In this case, the default is false.

See "Scoping the Session Cookie Path".

coherence-sessioncollection-class

This is the fully-qualified class name of the HttpSessionCollection implementation to use. Possible values include:

- com.tangosol.coherence.servlet.MonolithicHttpSessionCollection

- com.tangosol.coherence.servlet.SplitHttpSessionCollection (default)

- com.tangosol.coherence.servlet.TraditionalHttpSessionCollection

A value must be specified for this parameter. See "Configuring a Session Model".

coherence-shutdown-delay-seconds

This value determines how long the session management implementation waits before shutting down after receiving the last indication that the application has been stopped, either from ServletContextListener events (Servlet 2.3 or later) or by the destruction of Servlet and Filter objects. This value is expressed in seconds. A value of zero indicates synchronous shutdown; any positive value indicates asynchronous shutdown.

If unspecified, this parameter defaults to 0, because some servers are not capable of asynchronous shutdown.

coherence-sticky-sessions

If true, this value specifies whether sticky session optimizations will be used. This should be enabled only if a sticky load balancer is being used. This feature requires member, application or thread locking to be enabled. See "Enabling Sticky Session Optimizations".

See also coherence-session-thread-locking, coherence-session-member-locking, and coherence-session-app-locking in this table.

If unspecified, this parameter defaults to false.

B Capacity Planning

This appendix helps you estimate the number of cache servers that an application will need. These equations will help you only to arrive at a reasonable estimate; they do not account for the effects of cache indexes, nonapplication objects that might reside on the cache server heap, failover headroom, and so on.

To find the number of cache servers that you will need, you must first calculate the application's heap requirements and the cache server's available tenured generation.

1. Calculate your application's total heap requirements.
When trying to determine the number of cache servers that you will need for your application, a good starting point is to determine your application's total heap requirements. The total heap requirement can be calculated as the number of sessions that you will run, multiplied by the average number of cached objects per session, multiplied by average number of bytes per cached object. Because you typically make one backup copy per cache entry, multiply the total by 2. Written as an equation, this becomes:

Total_Heap_Requirement = 2 * (Number_of_Sessions) * (Average_Number_of_Cached_Objects per Session) * (Average_Number_of_Bytes per Cached_Object)

The units of measure for Total_Heap_Requirement are bytes. The Average_Number_of_Bytes per Cached_Object, means the number of bytes in the serialized byte stream of primary copies only. Note that this equation does not address unserialized object size. Space requirements for backup copies are accounted for separately.

2. Calculate the available tenured generation in a cache server JVM.
The available tenured generation is a function of the maximum heap size allocation and other user-specified JVM heap-sizing parameters. Another factor in the available tenured generation is the percentage of the heap that is available for storage. Typically, 66% is used as the maximum percentage of the heap available for storage, but this figure might be too low for your system. Make it a variable:

Percent_of_Heap_Available_for_Storage = 0.66

Available_Tenured_Generation = (Maximum_Heap_Size) * (Percent_of_Heap_Available_for_Storage)

3. Calculate the number of cache servers that will be needed.
To calculate the number of cache servers that will be needed, divide the total heap requirement by the available tenured generation.

Number_of_Cache_Servers = (Total_Heap_Requirement / Available_Tenured_Generation)

C Session Cache Configuration File

This appendix describes the contents of the session cache configuration file session-cache-config.xml, parametersdefault-session-cache-config.xml. Coherence*Web uses the caches and services defined in the file to implement HTTP session management. This file is deployed in the WEB-INF/classes directory.Table C-1 describes the default cache-related values used in the default-session-cache-config.xml file.

Table C-1 Cache-Related Values Used in default-session-cache-config.xml

Value

Description

local-attribute-storage

This local cache is used to store attributes that are not distributed. This can happen under these conditions:

- A coherence-distributioncontroller-class is configured. Attributes for local sessions will be stored in this cache.

- A non-serializable attribute is set on a distributed session. If coherence-preserve-attributes is set to true, then non-serializable attributes will be placed in the cache. Table A-1 describes this parameter.

local-session-storage

This local cache is used to store session models that are considered to be local by the configured (if any) coherence-distributioncontroller-class parameter. Table A-1 describes this parameter.

servletcontext-storage

If ServletContext attribute clustering (see the coherence-servletcontext-clustered parameter in Table A-1) is enabled (it is disabled by default), this cache is used to store ServletContext attributes. This cache is replicated by default, because it is expected that there will a few read-mostly attributes.

session-management

This cache is used to store internal configuration and management information for the session management implementation. This information is updated infrequently; therefore, it is a replicated cache by default.

session-overflow

If the coherence-sessioncollection-class parameter (described in Table A-1) is set to com.tangosol.coherence.servlet.SplitHttpSessionCollection, then this cache will hold large session attributes. By default, session attributes larger than 1 K will be stored in this cache. This is configured as a distributed cache.

Table C-2 describes the services-related values used in the default-session-cache-config.xml file.

Table C-2 Services-Related Values Used in default-session-cache-config.xml

Value

Description

DistributedSessions

This distributed service is used by the following caches:

- session-storage

- session-overflow

The coherence.session.localstorage system property controls if a JVM stores and manages data for these caches. Under most circumstances, this should be set to false for Web container JVMs. See "Deployment Topologies" for more details.

ReplicatedSessionsMisc

This replicated service is used by the session-management and servletcontext-storage caches.

SessionOwnership

This invocation service is used by the sticky session optimization feature (if coherence-sticky-sessions is set to true).

Example C-1 illustrates the contents of the default-session-cache-config.xml file. The cache- and services-related values described in Table C-1 and Table C-2 appear in bold.

Example C-1 Contents of the default-session-cache-config.xml File

<?xml version="1.0"?>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<!--                                                                       -->
<!--      Cache configuration descriptor for Coherence*Web                 -->
<!--                                                                       -->
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->

<cache-config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://xmlns.oracle.com/coherence/coherence-cache-config"
xsi:schemaLocation="http://xmlns.oracle.com/coherence/coherence-cache-config coherence-cache-config.xsd">

<scope-name>oracle.coherence.web</scope-name>

<caching-scheme-mapping>
<!--
The clustered cache used to store Session management data.
-->
<cache-mapping>
<cache-name>session-management</cache-name>
<scheme-name>replicated</scheme-name>
</cache-mapping>

<!--
The clustered cache used to store ServletContext attributes.
-->
<cache-mapping>
<cache-name>servletcontext-storage</cache-name>
<scheme-name>replicated</scheme-name>
</cache-mapping>

<!--
The clustered cache used to store Session attributes.
-->
<cache-mapping>
<cache-name>session-storage</cache-name>
<scheme-name>session-distributed</scheme-name>
</cache-mapping>

<!--
The clustered cache used to store the "overflowing" (split-out due to size)
Session attributes. Only used for the "Split" model.
-->
<cache-mapping>
<cache-name>session-overflow</cache-name>
<scheme-name>session-distributed</scheme-name>
</cache-mapping>

<!--
The local cache used to store Sessions that are not yet distributed (if
there is a distribution controller).
-->
<cache-mapping>
<cache-name>local-session-storage</cache-name>
<scheme-name>unlimited-local</scheme-name>
</cache-mapping>

<!--
The local cache used to store Session attributes that are not distributed
(if there is a distribution controller or attributes are allowed to become
local when serialization fails).
-->
<cache-mapping>
<cache-name>local-attribute-storage</cache-name>
<scheme-name>unlimited-local</scheme-name>
</cache-mapping>
</caching-scheme-mapping>

<caching-schemes>
<!--
Replicated caching scheme used by the Session management and ServletContext
attribute caches.
-->
<replicated-scheme>
<scheme-name>replicated</scheme-name>
<service-name>ReplicatedSessionsMisc</service-name>
<request-timeout>30s</request-timeout>
<backing-map-scheme>
<local-scheme>
<scheme-ref>unlimited-local</scheme-ref>
</local-scheme>
</backing-map-scheme>
<autostart>true</autostart>
</replicated-scheme>

<local-scheme>
<scheme-name>session-front</scheme-name>
<eviction-policy>HYBRID</eviction-policy>
<high-units>1000</high-units>
<low-units>750</low-units>
</local-scheme>

<distributed-scheme>
<scheme-name>session-distributed</scheme-name>
<service-name>DistributedSessions</service-name>
<thread-count system-property="coherence.session.threads">4
</thread-count>
<lease-granularity>member</lease-granularity>
<local-storage system-property="coherence.session.localstorage">
false</local-storage>
<partition-count>257</partition-count>
<backup-count>1</backup-count>
<request-timeout>30s</request-timeout>
<backing-map-scheme>
<ramjournal-scheme>
<high-units system-property="coherence.session.highunits"/>
<unit-calculator>BINARY</unit-calculator>
</ramjournal-scheme>
</backing-map-scheme>
<autostart>true</autostart>
</distributed-scheme>

<!--
Local caching scheme definition used by all caches that do not require an
eviction policy.
-->
<local-scheme>
<scheme-name>unlimited-local</scheme-name>
<service-name>LocalSessionCache</service-name>
</local-scheme>

<!--
Clustered invocation service that manages sticky session ownership.
-->
<invocation-scheme>
<service-name>SessionOwnership</service-name>
<request-timeout>30s</request-timeout>
</invocation-scheme>
</caching-schemes>
</cache-config>

D Oracle Coherence*Web Extension for OVAB

This appendix describes Coherence*Web extensions for Oracle Virtual Assembly Builder, a tool for virtualizing installed Oracle components, modifying those components, and then deploying them into your own environment. Using Oracle Virtual Assembly Builder, you capture the configuration of existing software components in artifacts called software appliances. Appliances can then be grouped, and their relationships defined into artifacts called software assemblies which provide a blueprint describing a complete multi-tier application topology.

The Oracle Coherence*Web introspection extension for Coherence*Web extends the functionality of the WebLogic Server Introspector. It examines the configuration of Coherence cache clusters and servers configured as part of a WebLogic domain.

This appendix has the following sections:

- Versions Supported

- Coherence*Web Introspection Parameters

- Reference System Prerequisites

- Requirements

- Resulting Artifact Type

- Wiring

- Wiring Properties

- Coherence*Web Appliance Properties

- Supported Template Types

D.1 Versions Supported

The plug-in extension works with Oracle WebLogic Server 11gR1 version 11.1.1.4.0, which includes Coherence 3.6.

D.2 Coherence*Web Introspection Parameters

There are no additional parameters required beyond those needed by Oracle WebLogic Server. For the parameters required by WebLogic Server, see “Using the Introspection Plug-in for Oracle Virtual Assembly Builder," in Administering Server Environments for Oracle WebLogic Server.

D.3 Reference System Prerequisites

There are no additional prerequisites beyond those defined by Oracle WebLogic Server. For the prerequisites required by WebLogic Server, see “Using the Introspection Plug-in for Oracle Virtual Assembly Builder," in Administering Server Environments for Oracle WebLogic Server.

D.4 Requirements

Oracle Coherence*Web has the following requirements:

Note:

In addition to the Coherence*Web requirements described in this section, all of WebLogic Server requirements must also be satisfied. For the WebLogic Server requirements, see “Using the Introspection Plug-in for Oracle Virtual Assembly Builder," in Administering Server Environments for Oracle WebLogic Server.

D.4.1 Deployment Model Requirement

The plug-in extension requires you to use an out-of-process deployment model for Oracle Coherence*Web, in which storage-enabled cache servers are executed as separate processes rather than running within Oracle WebLogic Server. For more information on the out-of-process deployment model, see "Out-of-Process Topology".

D.4.2 Requirement to Manually Update Custom Cluster Configuration Files

The plug-in extension examines Oracle Coherence*Web configuration defined through the WebLogic Server Administration Console and WebLogic Server MBeans (including WLST). It does not examine or modify custom cluster configuration files such as tangosol-coherence-override.xml. Custom cluster configuration files are passed through to the deployed environment, but no configuration changes are made to those files to reflect the deployed environment.

After deployment, ensure that you make appropriate manual configuration changes to any custom cluster configuration files.

D.5 Resulting Artifact Type

For each Coherence cluster that is defined in an introspected WebLogic domain, the plug-in extension creates a new appliance within the atomic Oracle WebLogic Server assembly.

D.6 Wiring

No wiring can be performed for Coherence cluster appliances. Each cluster appliance has a fixed, pre-defined connection to the domain's Administration Server, which is used at rehydration time to modify the cluster's configuration.

D.7 Wiring Properties

None.

D.8 Coherence*Web Appliance Properties

Each Oracle Coherence*Web cluster appliances has the following system and user properties:

Table D-1 describes Oracle Coherence*Web cluster appliance system properties:

Table D-1 Oracle Coherence*Web Appliance System Properties

Name

Type

Req'd

Default

Description

cache-servers

String

false

none

A list of the cache servers that are part of the cluster.

targets

String

false

none

A list of WebLogic Server Managed Servers that are part of the cluster.

<cacheserver>.node-manager-type

String

false

none

For each cache server in the above list, there is a property indicating the Node Manager type.

well-known-addresses

String

false

none

A list of well-known-addresses defined for the cluster. If no well-known-address are defined for this cluster (meaning it uses multicast), then this property will not be present.

<wellknownaddress>.server

String

false

none

For each of the well-known-addresses in the above list, there is a property indicating which cache server the well known address maps to (based on matching listen address and port information).

Table D-2 describes Oracle Coherence*Web cluster appliance user properties:

Table D-2 Oracle Coherence*Web Appliance User Properties

Name

Type

Req'd

Default

Description

<cacheserver>.node-manager-port

String

false

none

For each of the cache servers in the cluster, the Node Manager port is listed and may be modified by the user.

<cacheserver>.unicast-listen-port

String

false

none

For each of the cache servers in the cluster, the unicast listen port of that server is listed and may be modified by the user.

multicast-listen-address

String

false

none

The cluster-wide multicast listen address. If one or more well-known-addresses are listed (meaning the cluster uses unicast for cluster discovery), then this multicast property will not be present.

multicast-listen-port

String

false

none

The cluster-wide multicast listen port. If one or more well-known-addresses are listed (meaning the cluster uses unicast for cluster discovery), then this multicast property will not be present.

unicast-listen-port

String

false

none

The default unicast listen port for the cluster. This value is used by any cache servers that do not have a unicast listen port defined, as well as by any WebLogic Server Managed Servers that join the cluster.

<wellknownaddress>.server

String

true

none

If any of the defined well known addresses could not be correlated with a cache server (based on matching listen address and port information), they will be listed here, and the user is responsible for specifying a cache server name to be used as the well known address. This property is mandatory, meaning it must be specified either as an appliance property or via a deployment plan.

D.9 Supported Template Types

The supported template type is Oracle Enterprise Linux (OEL).

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