Thread Pools - Sun Microsystems GlassFish Enterprise Server 2.1 Administration Manual

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Thread Pools

The Java Virtual Machine (JVM) can support many threads of execution at once. To help
performance, the Enterprise Server maintains one or more thread pools. It is possible to assign
specific thread pools to connector modules and to the ORB.
One thread pool can serve multiple connector modules and enterprise beans. Request threads
handle user requests for application components. When the server receives a request, it assigns
the request to a free thread from the thread pool. The thread executes the client's requests and
returns results. For example, if the request needs to use a system resource that is currently busy,
the thread waits until that resource is free before allowing the request to use that resource.
Specify the minimum and maximum number of threads that are reserved for requests from
applications. The thread pool is dynamically adjusted between these two values. The minimum
thread pool size that is specified signals the server to allocate at least that many threads in
reserve for application requests. That number is increased up to the maximum thread pool size
that is specified.
Increasing the number of threads available to a process allows the process to respond to more
application requests simultaneously.
Avoid thread starvation, where one resource adapter or application occupies all threads in the
Enterprise Server, by dividing the Enterprise Server threads into different thread-pools.
This chapter contains the following topics:
"Working with Thread Pools" on page 164
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