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adjusted example of long-poller for a timeout aware source (queue channel)

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This commit is contained in:
Mark Fisher
2009-07-04 00:35:57 +00:00
parent 2377c9eb5f
commit a108461b47
1 changed files with 13 additions and 13 deletions
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26
spring-integration-reference/src/endpoint.xml
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@@ -252,19 +252,19 @@ consumer.setTransactionManager(txManager);</programlisting>
<para>
As mentioned in the background section for Polling Consumers above, you can also configure a Polling Consumer
in such a way as to emulate event-driven behavior. With a long receive-timeout and a short interval-trigger,
you can ensure a very timely reaction to arriving messages even on a polled message source.
</para>
<para>
A good use case that demonstrates how this approach could be applied is event-driven files via Spring
Integration's <code>inbound-channel-adapter</code> in the <code>file</code> namespace where a file dropped
into a directory would essentially become an event. That file will be picked up nearly instantaneously and
sent through the process.
<programlisting language="xml"><![CDATA[ <file:inbound-channel-adapter id="filesIn"
directory="file:${input.directory.property}">
<si:poller receive-timeout="30000">
<si:interval-trigger interval="10"/>
</si:poller>
</file:inbound-channel-adapter>]]></programlisting>
you can ensure a very timely reaction to arriving messages even on a polled message source. Note that this
will only apply to sources that have a blocking wait call with a timeout. For example, the File poller does
not block, each receive() call returns immediately and either contains new files or not. Therefore, even if
a poller contains a long receive-timeout, that value would never be usable in such a scenario. On the other
hand when using Spring Integration's own queue-based channels, the timeout value does have a chance to
participate. The following example demonstrates how a Polling Consumer will receive Messages nearly
instantaneously.
<programlisting language="xml"><![CDATA[ <service-activator input-channel="someQueueChannel"
output-channel="output">
<poller receive-timeout="30000">
<interval-trigger interval="10"/>
</poller>
</service-activator>]]></programlisting>
Using this approach does not carry much overhead since internally it is nothing more then a timed-wait thread
which does not require nearly as much CPU resource usage as a thrashing, infinite while loop for example.
</para>