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https://issues.apache.org/activemq/browse/CAMEL-2001?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=54110#action_54110
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Marat Bedretdinov commented on CAMEL-2001:
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Fintan,
I haven't looked at the way transactedInOut=false has been implemented but I'd
like to get a few clarifications on what you said.
1. On one hand you say that "Meaningful transactions are generally used to
bracket multiple (i.e. >1) updates of a persistent resource." Then you say "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."
So should I understand that you want to control how many messages per
transaction a given route would consume and then produce, or it would be okay
to consumer and produce a single message within context of a single transaction?
But speaking more generally I'm not convinced that an InOut exchange pattern
should be transacted. See the consumer that collects the reply of an InOut
exchange has a its life cycle constrained by the life cycle of the producer
that sent a request message.
So should the producer succeed at producing the request, then committing the
request and then should the router then crash the reply consumer will never be
restored and the reply never received and forwarded.
This is also true for the client application initiating a two way exchange. If
application crashes in the middle of the request the reply will be lost to this
application.
In my mind there is a way to implement this, but requires a lot more work than
just changing the camel jms component.
Lastly it is currently possible to achieve meaningful transactional behavior
with two transacted InOnly routes (cross broker including) and application
doing the correlation if a request/reply pattern is what is required.
> 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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