how to remove messages from deadletter queue after sucess elsewhere

[maxvar]

I currently have system A connected with system B where A sends an updated document every time it changes in it. The document is sent through a webservice provider deployed in the bus and serving as a route endpoint.

The set of routes is like this:

(1)

from(cxf:myWebServiceCatchingChanges).to(activemq:Notifications).process(...GiveOKResponseAlways...)

(2)

onException().....to(activemq:BadPartnersData)

onException().....to(activemq:NotImplementedYet)

onException().....to(activemq:OtherUnpredictedTroubles)

from("activemq:Notifications").process(...ProcessTheDocumentBasedOnCurrentUnderstandingHowTheUniverseRuns...)

The general document update structure of is stable, but the processor isnot 100% ready to cover for all possibilities that can be exploited in app.A.

Different exceptions caught in "ProcessTheDocumentBasedOnCurrentUnderstandingHowTheUniverseRuns" lead to the message being routed to one of three queues:

BadPartnersData - it indicates that something related to Partners details is not OK in App.A and (only manual) corrections should be done there. The messages are looked through and forwarded to stuff responsible to process data changes in App.A.

NotImplementedYet - when the processor understands that something is missing in it and needs code improvement from developers.

OtherUnpredictedTroubles is a genereal-purpose deadletter queue when something cannot be reprocessed in any number or retries.

After changes of partners data in App.A or improvement in the processor component code the updated document (or maybe the same one) is sent (or pushed) from App.A to the web-service again.

If the result of ProcessTheDocumentBasedOnCurrentUnderstandingHowTheUniverseRuns is then OK then it makes sense to remove all the badmail related to the document from BadPartnersData, NotImplementedYet, OtherUnpredictedTroubles. I think activemq correlation id based on persistent document ID can somehow be used for this.

The question is how to implement it using Camel. I did not find a similar case in the samples or Google search.

Maybe I need not a change in Java code but a different point of view on the subject?

Regards,

Maxim

[davsclaus]

Since you use queues in ActiveMQ as your dead letter queues, then you can use any kind of AMQ tool to remove those. Or use some Java code with JMS API to remove the messages etc.

For example if you use JMX then you can from the JMX console remove / purge queues in ActiveMQ.

[maxvar]

Thanks to extended functional requirements I now have to actually process all messages, so the updated scenario becomes like this:

• The MAIN processor throws several different types of exception.

• The processor in the route after the MAIN sends "ok" message to the log-queue.

• Route-level onException handlers redirect failed exchanges to separate amq queues.

• The consumers get the messages, send mail to users or admins or developers and send the notification to the log-queue.

• The consumer from the log-queue stores "error" messages to the database (using ibatis) or erases all related records from the db when it gets "ok" message.

Still, it could be a good idea to have a camel component which can manage activemq (remove/update messages using selector+instructions in the body/headers).

[maxvar]

(Just got to my own thread looking for something...)

Currently I do not think it's a good idea anymore.

Good read on why it's not and why I should have used a db instead: http://java.dzone.com/articles/messaging-anti-patterns-part-1