Programming WebLogic JTA

Troubleshooting Transactions

This section describes troubleshooting tools and tasks for use in determining why transactions fail and deciding what actions to take to correct the problem.

This section discusses the following topics:

Overview

WebLogic Server includes the ability to monitor currently running transactions and ensure that adequate information is captured in the case of heuristic completion. It also provides the ability to monitor performance of database queries, transactional requests, and bean methods.

Troubleshooting Tools

WebLogic Server provides the following aids to transaction troubleshooting:

Exceptions

WebLogic JTA supports all standard JTA exceptions. For more information about standard JTA exceptions, see the Javadoc for the javax.transaction and javax.transaction.xa package APIs.

In addition to the standard JTA exceptions, WebLogic Server provides the class weblogic.transaction.RollbackException. This class extends javax.transaction.RollbackException and preserves the original reason for a rollback. Before rolling a transaction back, or before setting it to rollbackonly, an application can supply a reason for the rollback. All rollbacks triggered inside the transaction service set the reason (for example, timeouts, XA errors, unchecked exceptions in beforeCompletion, or inability to contact the transaction manager). Once set, the reason cannot be overwritten.

Transaction Identifier

The Transaction Service assigns a transaction identifier (Xid) to each transaction. This ID can be used to isolate information about a specific transaction in a log file. You can retrieve the transaction identifier using the getXID method in the weblogic.transaction.Transaction interface. For detailed information on methods for getting the transaction identifier, see the weblogic.transaction.Transaction Javadoc.

Transaction Name and Properties

WebLogic JTA provides extensions to javax.transaction.Transaction that support transaction naming and user-defined properties. These extensions are included in the weblogic.transaction.Transaction interface.

The transaction name indicates a type of transaction (for example, funds transfer or ticket purchase) and should not be confused with the transaction ID, which identifies a unique transaction on a server. The transaction name makes it easier to identify a transaction type in the context of an exception or a log file.

User-defined properties are key/value pairs, where the key is a string identifying the property and the value is the current value assigned to the property. Transaction property values must be objects that implement the Serializable interface. You manage properties in your application using the set and get methods defined in the weblogic.transaction.Transaction interface. Once set, properties stay with a transaction during its entire lifetime and are passed between machines as the transaction travels through the system. Properties are saved in the transaction log, and are restored during crash recovery processing. If a transaction property is set more than once, the latest value is retained.

For detailed information on methods for setting and getting the transaction name and transaction properties, see the weblogic.transaction.Transaction Javadoc.

Transaction Status

The Java Transaction API provides transaction status codes using the javax.transaction.Status class. Use the getStatusAsString method in weblogic.transaction.Transaction to return the status of the transaction as a string. The string contains the major state as specified in javax.transaction.Status with an additional minor state (such as logging or pre-preparing).

Transaction Statistics

Transaction statistics are provided for all transactions handled by the transaction manager on a server. These statistics include the number of total transactions, transactions with a specific outcome (such as committed, rolled back, or heuristic completion), rolled back transactions by reason, and the total time that transactions were active. For detailed information on transaction statistics, see the Administration Console Online Help.

Transaction Monitoring

The Administration Console allows you to monitor transactions. Monitoring tasks are performed at the server level. Transaction statistics are displayed for a specific server.

Debugging JTA Resources

Once you have narrowed the problem down to a specific application, you can activate WebLogic Server’s debugging features to track down the specific problem within the application.

Enabling Debugging

You can enable debugging by setting the appropriate ServerDebug configuration attribute to "true." Optionally, you can also set the server StdoutSeverity to "Debug".

You can modify the configuration attribute in any of the following ways.

Enable Debugging Using the Command Line

Set the appropriate properties on the command line. For example,

-Dweblogic.debug.DebugJDBCJTA=true 
-Dweblogic.log.StdoutSeverity="Debug"

This method is static and can only be used at server startup.

Enable Debugging Using the WebLogic Server Administration Console

Use the WebLogic Server Administration Console to set the debugging values:

Enable Debugging Using the WebLogic Scripting Tool

Use the WebLogic Scripting Tool (WLST) to set the debugging values. For example, the following command runs a program for setting debugging values called debug.py:

java weblogic.WLST debug.py

The debug.py program contains the following code:

user='user1'
password='password'
url='t3://localhost:7001'
connect(user, password, url)
edit()
cd('Servers/myserver/ServerDebug/myserver')
startEdit()
set('DebugJDBCJTA','true')
save()
activate()

Note that you can also use WLST from Java. The following example shows a Java file used to set debugging values:

import weblogic.management.scripting.utils.WLSTInterpreter;
import java.io.*;
import weblogic.jndi.Environment;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class test {
	 public static void main(String args[]) {
	try {
		WLSTInterpreter interpreter = null;
		String user="user1";
		String pass="pw12ab";
		String url ="t3://localhost:7001";
		Environment env = new Environment();
		env.setProviderUrl(url);
		env.setSecurityPrincipal(user);
		env.setSecurityCredentials(pass);
		Context ctx = env.getInitialContext();

		interpreter = new WLSTInterpreter();
		interpreter.exec
			("connect('"+user+"','"+pass+"','"+url+"')");
		interpreter.exec("edit()");
		interpreter.exec("startEdit()");
		interpreter.exec
			("cd('Servers/myserver/ServerDebug/myserver')");
		interpreter.exec("set('DebugJDBCJTA','true')");
		interpreter.exec("save()");
		interpreter.exec("activate()");

	} catch (Exception e) {
	System.out.println("Exception "+e);
	}
	}
}

Using the WLST is a dynamic method and can be used to enable debugging while the server is running.

Changes to the config.xml File

Changes in debugging characteristics, through console, or WLST, or command line are persisted in the config.xml file. See Figure 13-1:

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.
.

<server>
<name>myserver</name>
<server-debug>
<debug-scope>
<name>weblogic.transaction</name>
<enabled>true</enabled>
</debug-scope>
<debug-jdbcjta>true</debug-jdbcjta>
</server-debug>
</server> 

.
.
.

This sample config.xml fragment shows a transaction debug scope (set of debug attributes) and a single JTA attribute.

JTA Debugging Scopes

It is possible to see the tree view of the DebugScope definitions using java weblogic.diagnostics.debug.DebugScopeViewer.

You can enable the following registered debugging scopes for JTA: