Configuring JMS Resources for Clustering and High Availability - Oracle WebLogic Server 12c Advanced Administration - page 102

Introduction
The Java Message Service (JMS) is a standard Java API that enables an enterprise
application to communicate asynchronously with other applications by sending and receiving
messages. The Oracle WebLogic Server 12 c messaging subsystem is fully compatible with the
JMS 1.1 specification.
The JMS API defines two models of communication: point-to-point and publisher/subscriber.
Point-to-point communication uses a JMS queue and publisher/subscriber communication
uses a JMS topic. Although similar in configuration, JMS queues and JMS topics are
destinations that work in very different ways.
In the point-to-point model, a sender first publishes and enqueues a message to the queue.
The message is then dequeued and processed by the single consumer that is listening to
this queue. The enqueue and dequeue processes are independent, loosely coupled, and
asynchronous. The message can be held by the queue until a consumer starts listening for
incoming messages. In the point-to-point model, the message is delivered to only one recipient.
In the publisher/subscriber model, a publisher sends a message to a topic and this message
is consumed by every subscriber of the topic. In the publisher/subscriber model, the message
can be delivered to multiple recipients.
A hypothetical scenario with an JMSApp enterprise application deployed in PROD_Cluster
will be used as an example in this chapter. The application requires performance and high
availability and uses a JMS queue under the JNDI name jms.appqueue , and a connection
factory with the JNDI name jms.appcf . A clustered JMS offers a more reliable solution than
a JMS in a single Managed Server. The platform can be scaled when needed and the load is
distributed across multiple Managed Servers.
The following recipes contain the steps needed by a WebLogic Administrator to properly
configure the JMSApp application to use the WebLogic JMS subsystem with clustering and
high availability. A specific JMS module will be created to isolate the configuration, which
includes the JMS servers and the JMS queue destination.
Creating the file stores
Oracle WebLogic Server 12 c makes use of its own storage solution, known as the Persistent
Store. The persistent store can be used by the JMS subsystem to persist the JMS messages of
a JMS destination. It can also be used by the transaction log (TLOG) for keeping information
of committed transactions on course or to store WLDF diagnostic information, among
other functionalities.
The persistent store can be file-based or JDBC-based. All WebLogic Server instances include a
default file-based persistent store. The default persistent store is located at $DOMAIN_HOME/
servers/<instance_name>/data/store/default .