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INT-3788: Fix Poller Doc (Memory Leak)

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JIRA: https://jira.spring.io/browse/INT-3788
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Gary Russell
2015-07-30 11:11:04 -04:00
committed by Artem Bilan
parent 448f9a52d2
commit 3c9b0e4e82
1 changed files with 12 additions and 5 deletions
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17
src/reference/asciidoc/endpoint.adoc
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@@ -519,25 +519,32 @@ However, there are certain things you must understand when configuring a Poller
The problem is that there are two configurations in place.
The _Poller_ and the _TaskExecutor_, and they both have to be in tune with each other otherwise you might end up creating an artificial memory leak.
Let's look at the following configuration provided by one of the users on the Spring Integration forum (http://forum.springsource.org/showthread.php?t=94519):
Let's look at the following configuration provided by one of the users on the
http://forum.spring.io/forum/spring-projects/integration/87155-spring-integration-poller-configuration[Spring Integration Forum]:
[source,xml]
----
<int:channel id="publishChannel">
<int:queue />
</int:channel>
<int:service-activator input-channel="publishChannel" ref="myService">
<int:poller receive-timeout="5000" task-executor="taskExecutor" fixed-rate="50"/>
<int:poller receive-timeout="5000" task-executor="taskExecutor" fixed-rate="50" />
</int:service-activator>
<task:executor id="taskExecutor" pool-size="20" queue-capacity="20"/>
<task:executor id="taskExecutor" pool-size="20" />
----
The above configuration demonstrates one of those out of tune configurations.
By default, the task executor has an unbounded task queue.
The poller keeps scheduling new tasks even though all the threads are blocked waiting for either a new message to arrive, or the timeout to expire.
Given that there are 20 threads executing tasks with a 5 second timeout, they will be executed at a rate of 4 per second (5000/20 = 250ms).
But, new tasks are being scheduled at a rate of 20 per second, so the internal queue in the task executor will grow at a rate of 16 per second (while the process is idle), so we essentially have a memory leak.
One of the ways to handle this is to set the `queue-capacity` attribute of the Task Executor to 0.
One of the ways to handle this is to set the `queue-capacity` attribute of the Task Executor; and even 0 is a reasonable
value.
You can also manage it by specifying what to do with messages that can not be queued by setting the `rejection-policy` attribute of the Task Executor (e.g., DISCARD).
In other words there are certain details you must understand with regard to configuring the TaskExecutor.
In other words, there are certain details you must understand with regard to configuring the TaskExecutor.
Please refer to - _Section 25 - Task Execution and Scheduling_ of the Spring reference manual for more detail on the subject.
[[endpoint-inner]]