Configuring the Task Scheduler

In Spring Integration, the ApplicationContext plays the central role of a message bus, and you need to consider only a couple of configuration options. First, you may want to control the central TaskScheduler instance. You can do so by providing a single bean named taskScheduler. This is also defined as a constant, as follows:

IntegrationContextUtils.TASK_SCHEDULER_BEAN_NAME

By default, Spring Integration relies on an instance of ThreadPoolTaskScheduler, as described in the Task Execution and Scheduling section of the Spring Framework reference manual. That default TaskScheduler starts up automatically with a pool of ten threads, but see Global Properties. If you provide your own TaskScheduler instance instead, you can set the 'autoStartup' property to false or provide your own pool size value.

When polling consumers provide an explicit task executor reference in their configuration, the invocation of the handler methods happens within that executor’s thread pool and not the main scheduler pool. However, when no task executor is provided for an endpoint’s poller, it is invoked by one of the main scheduler’s threads.

Do not run long-running tasks on poller threads. Use a task executor instead. If you have a lot of polling endpoints, you can cause thread starvation, unless you increase the pool size. Also, polling consumers have a default receiveTimeout of one second. Since the poller thread blocks for this time, we recommend that you use a task executor when many such endpoints exist, again to avoid starvation. Alternatively, you can reduce the receiveTimeout.

An endpoint is a Polling Consumer if its input channel is one of the queue-based (that is, pollable) channels. Event-driven consumers are those having input channels that have dispatchers instead of queues (in other words, they are subscribable). Such endpoints have no poller configuration, since their handlers are invoked directly.

When running in a JEE container, you may need to use Spring’s TimerManagerTaskScheduler, as described here, instead of the default taskScheduler. To do so, define a bean with the appropriate JNDI name for your environment, as the following example shows:

<bean id="taskScheduler" class="org.springframework.scheduling.concurrent.DefaultManagedTaskScheduler">
    <property name="jndiName" value="tm/MyTimerManager" />
    <property name="resourceRef" value="true" />
</bean>

When a custom TaskScheduler is configured in the application context (like the above mentioned DefaultManagedTaskScheduler), it is recommended to supply it with a MessagePublishingErrorHandler (integrationMessagePublishingErrorHandler bean) to be able to handle exceptions as ErrorMessage`s sent to the error channel, as is done with the default `TaskScheduler bean provided by the framework.

See also Error Handling for more information.