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From "Fintan Bolton (JIRA)" <j...@apache.org>
Subject [jira] Created: (CAMEL-2001) Transactions do not work properly with JMS producer endpoint when processing InOut exchanges
Date Wed, 09 Sep 2009 16:27:12 GMT
Transactions do not work properly with JMS producer endpoint when processing InOut exchanges
--------------------------------------------------------------------------------------------

                 Key: CAMEL-2001
                 URL: https://issues.apache.org/activemq/browse/CAMEL-2001
             Project: Apache Camel
          Issue Type: Bug
          Components: camel-jms
    Affects Versions: 2.0.0
            Reporter: Fintan Bolton
             Fix For: Future


You cannot really use transactions with a JMS producer endpoint when processing _InOut_ exchanges.
Depending on the scenario, the route either hangs or the implemented behavior is not very
useful.

Here is a summary of the current (not very useful) behavior:

After experimenting with JMS transacted endpoints for a bit and looking at the source, here
is what I found the behavior to be for JMS producer endpoints:

# On the request leg (sending the JMS message), if there is no existing transaction context,
the producer will either create a transaction for sending the message (if {{transactedInOut=true}}
or not (if {{transactedInOut=false). In any case, since the transaction only lasts as long
as it takes to push the message onto the outoing queue, it is not particularly interesting.
Meaningful transactions are generally used to bracket multiple (i.e. >1) updates of a persistent
resource.
# On the request leg, if there *is* an existing transaction context, the producer joins the
current transaction (irrespective of the value of {{transactedInOut}}), provisionally writes
the message to the outgoing queue, and then starts waiting for the reply. In this case, the
route hangs, because the send is never committed.
# On the reply leg, the message is received in a separate thread. This step is transactional,
but the transaction ends as soon as the message has been pulled off the queue, so it is also
not very interesting.


Here is what I think would be useful behavior for a JMS producer endpoint:

# On the request leg, if there is an existing transaction context, the producer joins the
current transaction, provisionally writes the message to the outgoing queue, and then *commits*
the current transaction directly afterwards. This prevents the route from hanging. *Note:*
There is some code in the {{CamelJmsTemplate}} class looks like it was intended to do this,
but it currently does not work. See child issue for more details.
# On the reply leg, create a new transaction in the main thread that includes the action of
pulling the reply off the incoming queue. This would require that the reply be received in
the main thread, not a sub-thread (as currently). Subsequent nodes in the route could then
participate in this transaction. Admittedly, this would be a tricky feature to implement,
because it would involve making a big change to the producer's threading model.

I'm shortly going to add a couple of child JIRAs here to explain some related issues.

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