DBMS_SAGA

10 DBMS_SAGA_ADM

The DBMS_SAGA_ADM package provides a collection of saga administration functions and procedures to define and manage saga participants, coordinators and brokers.

This chapter contains the following topics:

DBMS_SAGA_ADM Overview

The SYS.DBMS_SAGA_ADM package provides the saga administration APIs to manage sagas.

The saga administration APIs implemented using the DBMS_SAGA_ADM package enables the administrators to define and manage saga participants, coordinators and brokers. The package APIs are described here for your reference.

DBMS_SAGA_ADM Security Model

A participant must invoke the procedures in DBMS_SAGA_ADM package from inside its schema and PDB. Invocation of APIs in the DBMS_SAGA_ADM package requires the SAGA_ADM_ROLE role.

Summary of DBMS_SAGA_ADM Subprograms

This table lists and briefly describes the DBMS_SAGA_ADM package subprograms.

Table 10-1 DBMS_SAGA_ADM Package Subprograms

Subprogram	Description
ADD_COORDINATOR Procedure	Adds a saga coordinator to the saga framework
DROP_COORDINATOR Procedure	Drops the given coordinator from the saga framework.
ADD_PARTICIPANT Procedure	Adds a participant to the local PDB and the broker
DROP_PARTICIPANT Procedure	Drops the given participant on the local PDB and the broker if there are no pending sagas and pending saga messages for the participant.
ADD_BROKER Procedure	Adds a broker to the saga framework and creates a JMS topic for the broker.
DROP_BROKER Procedure	Drops a broker and the associated JMS topic.
REGISTER_SAGA_CALLBACK Procedure	Allows users to create or modify a callback package if created using `add_participant` procedure.

ADD_BROKER Procedure

This procedure adds a broker to the saga framework.

As a part of adding a broker, a JMS topic is created for the broker. Both incoming and outgoing message propagation channels from participants to the broker use the broker's JMS topic.

Syntax

add_broker(
 broker_name                  IN varchar2,
 broker_schema                IN varchar2 default sys_context('userenv', 'CURRENT_USER'),
 storage_clause               IN varchar2 default NULL,
 queue_partitions             IN number DEFAULT 1,
 version                      IN number default 1
 );

Parameters

Table 10-2 ADD_BROKER Procedure Parameters

Parameter	Description
`broker_name`	A unique broker name.
`broker_schema`	The schema for the microservice participant being added. If no value is provided, `CURRENT_USER` is used.
`storage_clause`	The storage parameter is included in the `CREATE_TRANSACTIONAL_EVENT_QUEUE` statement when the inbound and outbound JMS topics are created. The `storage_clause` argument can take any text that you can use in a standard `DBMS_AQADM.CREATE_TRANSACTIONAL_EVENT_QUEUE` `storage_clause` argument.
`queue_partitions`	The number of partitions for the Saga entity IN/OUT queues. This allows for higher parallelism and throughput for the Saga entity. `DEFAULT` is 1.
`version`	Saga version

DROP_BROKER Procedure

This procedure drops a broker and the associated JMS topic.

A broker can only be dropped if there are no registered participants and pending messages for the broker.

Syntax

drop_broker(broker_name      IN varchar2)

Parameters

Table 10-3 DROP_BROKER Procedure Parameters

Parameter	Description
`broker_name`	The broker name to be dropped.

ADD_COORDINATOR Procedure

This procedure adds a Saga coordinator to the Saga framework. A Saga coordinator acts as a transaction manager for Sagas. The Saga coordinator maintains the state of a Saga across various participants.

Syntax

add_coordinator(
 coordinator_name       IN varchar2,
 coordinator_schema     IN varchar2 DEFAULT sys_context(‘USERENV’, ‘CURRENT_USER’),
 storage_clause         IN varchar2 DEFAULT NULL,
 dblink_to_broker       IN varchar2 DEFAULT NULL,
 mailbox_schema         IN varchar2,
 broker_name            IN varchar2,
 dblink_to_coordinator  IN varchar2 DEFAULT NULL,
 queue_partitions       IN number DEFAULT 1,
 listener_count         IN number DEFAULT -1,
 version                IN number default 1);

Parameters

Table 10-4 ADD_COORDINATOR Procedure Parameters

Parameter	Description
`coordinator_name`	A unique name for the Saga coordinator.
`coordinator_schema`	The schema for the Saga coordinator being added. The parameter uses `CURRENT_USER` if no value is specified.
`storage_clause`	The storage parameter is included in the `CREATE_TRANSACTIONAL_EVENT_QUEUE` statement when the inbound and outbound JMS topics are created. The `storage_clause` argument can take any text that you can use in a standard `DBMS_AQADM.CREATE_TRANSACTIONAL_EVENT_QUEUE` `storage_clause` argument.
`dblink_to_broker`	Pre-created database link to connect from the coordinator PDB to the broker PDB.
`mailbox_schema`	The schema for the mailbox owner at the broker.
`broker_name`	The name of the broker.
`dblink_to_coordinator`	Pre-created database link to connect from the broker PDB to the coordinator PDB.
`queue_partitions`	The number of partitions for the Saga entity IN/OUT queues. This allows for higher parallelism and throughput for the Saga entity. `DEFAULT` is 1. Note: The number of queue partitions should be equal to the partition count specified while performing the `add_broker()` operation.
`listener_count`	The number of concurrent Saga listener processes consuming inbound messages for the Saga coordinator. `listener_count` can have one of the following values: `DBMS_SAGA_ADM.AQ_NTFN`, which is also the `DEFAULT`. In this case, the Saga coordinator processes messages using the AQ notification mechanism. `DBMS_SAGA_ADM.AUTO_NTFN`- In this case, the Saga coordinator processes messages using job queue processes that dequeue from the coordinator queue. The job automatically adds and removes jobs depending on the queue depth. If any positive number (N) is specified, then N number of fixed jobs are created to process the messages for the Saga coordinator.
`version`	Saga version

DROP_COORDINATOR Procedure

This procedure drops the given coordinator and disables message propagation between the coordinator and the broker. A coordinator can only be dropped if there are no participants associated with the coordinator.

Syntax

drop_coordinator(coordinator_name  IN varchar2)

Parameters

Table 10-5 DROP_COORDINATOR Procedure Parameters

Parameter	Description
`coordinator_name`	The name of the saga coordinator that is being dropped.

ADD_PARTICIPANT Procedure

This procedure adds a Saga participant to the database and the broker.

A participant name is unique to the broker where the participant is added. The ADD_PARTICIPANT procedure creates system-defined inbound and outbound JMS topics for the participant. A JMS topic is also created at the broker's side if the topic does not exist. Message propagation relationships are set up from:

The outbound JMS topic of the participant to the JMS topic of the broker.
The JMS topic of the broker to the inbound JMS topic of the participant.

Syntax

add_participant(
 participant_name            IN varchar2,
 participant_schema          IN varchar2 DEFAULT sys_context('USERENV', 'CURRENT_USER'),
 storage_clause              IN varchar2 DEFAULT NULL,
 coordinator_name            IN varchar2 DEFAULT NULL,
 dblink_to_broker            IN varchar2,
 mailbox_schema              IN varchar2,
 broker_name                 IN varchar2,
 callback_schema             IN varchar2 DEFAULT sys_context(‘USERENV’,’CURRENT_USER’),
 callback_package            IN varchar2,
 dblink_to_participant       IN varchar2,
 queue_partitions            IN number DEFAULT 1,
 version                     IN number DEFAULT 1
 );

Parameters

Table 10-6 ADD_PARTICIPANT Procedure Parameters

Parameter	Description
`participant_name`	A unique name for the saga participant.
`participant_schema`	The schema for the saga participant being added. The parameter uses `CURRENT_USER` if no value is specified.
`storage_clause`	The storage parameter is included in the `CREATE_TRANSACTIONAL_EVENT_QUEUE` statement when the inbound and outbound JMS topics are created. The `storage_clause` argument can take any text that you can use in a standard `DBMS_AQADM.CREATE_TRANSACTIONAL_EVENT_QUEUE` `storage_clause` argument.
`coordinator_name`	The name of the saga coordinator. If no value is provided and `create_coordinator` is `TRUE`, a system generated name is assumed.
`dblink_to_broker`	The pre-created database link to connect from the participant PDB to broker PDB.
`mailbox_schema`	The schema for the mailbox owner at the broker's side.
`broker_name`	The name of the broker. If no value is provided, the `mailbox_schema` name is assumed.
`callback_schema`	The schema of the user-defined callback package. If no value is provided, `CURRENT_USER` is used.
`callback_package`	The name of the user-defined callback package. The callback package isolates application developers from the internal details of the saga infrastructure, and enables the developers to focus on business logic.
`dblink_to_participant`	The pre-created database link to connect from broker PDB to the participant PDB.
`queue_partitions`	The number of partitions for the Saga entity IN/OUT queues. This allows for higher parallelism and throughput for the Saga entity. `DEFAULT` is 1. Note: The number of queue partitions should be equal to the partition count specified while performing the `add_broker()` operation.
`version`	Saga version

Usage Notes

The ADD_PARTICIPANT procedure needs coordinator name as an argument, hence the ADD_COORDINATOR procedure must be used before the ADD_PARTICIPANT procedure.

DROP_PARTICIPANT Procedure

This procedure drops the given participant on the local PDB and the broker.

The DROP_PARTICIPANT procedure drops the given participant on the local PDB and the broker if there are no pending sagas and pending saga messages for the participant. The DROP_PARTICIPANT procedure also disables message propagation between the participant and the broker.

Syntax

drop_participant(participant_name  IN varchar2)

Parameters

Table 10-7 DROP_PARTICIPANT Procedure Parameters

Parameter	Description
`participant_name`	The name of the participant microservice that is being dropped.

REGISTER_SAGA_CALLBACK Procedure

This procedure enables users to create or modify a callback package if the package is created using ADD_PARTICIPANT procedure.

If the callback package was not added before, the REGISTER_SAGA_CALLBACK procedure sets up the required subscribers and the notification callback. While doing an add participant the user has the option of specifying the callback package. If they want to defer specifying the callback package or if they want to change the callback package they can use the REGISTER_SAGA_CALLBACK procedure. If the callback already exists for a participant, then it is simply replaced. The REGISTER_SAGA_CALLBACK procedure is useful in cases where the user is not sure about whether to implement PL/SQL or Java, and wants to decide about it later, or the user wants to switch implementations (for example, from a Java client to a PL/SQL based client).

Syntax

register_saga_callback(participant_name IN varchar2,
 callback_schema        IN varchar2 default sys_context(‘USERENV’,’CURRENT_USER'),
 callback_package       IN varchar2);

Parameters

Table 10-8 REGISTER_SAGA_CALLBACK Procedure Parameters

Parameter	Description
`participant_name`	The name of the participant already created.
`callback_schema`	The schema for the user-defined callback package. If no value is provided, `CURRENT_USER` is used.
`callback_package`	The name of the user-defined callback package. The callback package isolates application developers from the internal details of the saga infrastructure, and enables them to focus on business logic.