Sun Java System Message Queue 3.7 UR1 Developer's Guide for Java Clients

Managing Client Threads

Using client threads effectively requires that you balance performance, throughput, and resource needs. To do this, you need to understand JMS restrictions on thread usage, what threads Message Queue allocates for itself, and the architecture of your applications. This section addresses these issues and offers some guidelines for managing client threads.

JMS Threading Restrictions

The Java Messaging Specification mandates that a session not be operated on by more than one thread at a time. This leads to the following restrictions:

The system does not enforce the requirement that a session be single threaded. If your client application violates this requirement, you will get a JMSIllegalState exception or unexpected results.

Thread Allocation for Connections

When the Message Queue client runtime creates a connection, it creates two threads: one for consuming messages from the socket, and one to manage the flow of messages for the connection. In addition, the client runtime creates a thread for each client session. Thus, at a minimum, for a connection using one session, three threads are created. For a connection using three sessions, five threads are created, and so on.

Managing threads in a JMS application often involves trade-offs between performance and throughput. Weigh the following considerations when dealing with threading issues.