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From Andrew Thorburn <>
Subject JMS - asyncConsumer & <threads>
Date Thu, 25 Sep 2014 02:07:36 GMT
Hey guys,

Just want to clarify that I understand how this works correctly:

Setting the "asyncConsumer" option to "true" on a JMS Consumer does not, in
and of itself, mean that messages are guaranteed to be processed
asynchronously, but it does mean that if an endpoint supports asynchronous
behaviour, the Camel JMS consumer will allow that.

In other words, if you set "asyncConsumer" to "true", but none of your
endpoints in your pipeline allow asynchronous processing, it will all get
processed synchronously anyway.

In that case, you would need to wrap everything you wanted processed
asynchronously in a <threads> tag (or a threads() call), which would allow
you to control the number of threads, the queue size, etc.

Conversely, even if you provide a <threads> wrapper, if asyncConsumer is
set to "false", it will get processed synchronously.

Is that correct? It appears to be, based on what I can see in the source
code (looking at Threads, JMS Configuration, JMS Consumer,
EndpointMessageListener, etc).

If that's correct, wouldn't it make sense to rename the option
asyncConsumer to asyncAllowed (or maybe asyncConsumerAllowed)?
asyncConsumer implies, at least to me, that the consumer will somehow
magically run everything asynchronously without the need for further
configuration, when that does not appear to be true. asyncAllowed is closer
to what actually happens - in that setting the option does not magically
make everything asynchronous, but if you *want* to make it asynchronous
yourself, you can.

Also, this implies that the example at the bottom of is, if not wrong, then at least missing
information, as it does not show that the JMS consumer has had the
"asyncConsumer" option set on it anywhere.

FWIW, as I'm integrating with WebSphere MQ, and the queue I'm consuming
from is set to EXCLUSIVE_OPEN (or something along those lines), I don't
believe that I can make any use of the
concurrentConsumers/maxConcurrentConsumers options on the JMS endpoint.


- Andrew Thorburn

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