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From gramanero <>
Subject Transacted vs DeadLetterQueue
Date Mon, 04 Jun 2012 19:51:19 GMT
I'm wondering if there are any sort of best practices or pros/cons to using
either the dead letter queue or transactions when errors occur while pulling
off messages from a queue and attempting to route them to a cxfrs endpoint
that may not be available.

For example, say I have the following route:

    <route id="myRoute" startupOrder="1" >
        <from uri="activemq:queue:myQueue"/>
        <to uri="cxfrs:http://localhost:9999/MyService" pattern="InOnly"/>

I have played around with using the dead letter queue and that seems to work
well, but then I started to think about getting the messages off the dead
letter queue and putting them back onto myQueue for processing once the
service becomes available. One way to accomplish this (possibly) is to use
the CronScheduledRoutePolicy such that it wakes up every hour and starts a
route that will pull messages off the dead letter queue (if there are any),
put them onto the myQueue and then stop the route after N number of minutes.
I'm not sure that this is a good idea, but it "one" way to build a more
auto-maintained system. Seems like once I start getting into configuring the
CronScheduledRoutePolicy that the solution becomes more complex then it
really needs to be in terms of the various moving parts.

The other thought is to use the ActiveMQ transaction manager. If the cxfrs
endpoint is not available, then the transaction rolls back which puts the
message back on the queue (or just never really pulls it off) and then waits
a while (via a delay configuration) and tries to route the message again.
One thing I don't really like about this is that if the service is down for
a long period of time, then it seems like we will be in this mode where
messages are constantly trying to be routed to the unavailable cxfrs
endpoint thus sort of thrashing the system.

I'm just looking for some opinions to how this type of problem is typically
solved or some sort of best practice to this use case.


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