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From Marco Zapletal <marco.zaple...@gmail.com>
Subject Camel ActiveMQ consumers do not consume after restart
Date Fri, 20 Jul 2012 14:25:51 GMT
Hi folks,

We have an application where we have two Camel contexts (C1, C2) which 
exchange messages via two queues (Q1, Q2). These queues are located on 
the same ActiveMQ broker. Thereby, the message flow goes as follows:

C1 -> Q1 -> C2
C2 -> Q2 -> C1

C2 uses furthermore some "internal" queues on the AMQ broker, but I 
guess they are not relevant to the problem.

The issue we are facing can be described as follows and happens only 
when C1 or C2 go down or have to be restarted

- In case, no messages are produced of either C1/C2 while the other one 
restarts, everything is fine - i.e., there is no problem with consuming 
messages

- In case, messages are produced of either C1/C2 and are put in the 
respective queue, during the absence of the other Camel application, we 
gonna face problems with consuming messages from the queues.
We have especially tested this scenario by stopping C2. C1 produces 
messages to Q1. Then we restart C2 again and (almost) nothing happened.

- By almost I mean, that the context of C2 starts up without errors. 
What is also observed is that when we have 1 concurrentConsumer defined 
in the AMQ consumer configuration in C2, 1 message is consumed (if 3 
concurrentConsumers are defined, 3 messages are consumed). Afterwards, 
consumption stops.

- When restarting C2 again, 1 message is consumed from Q1 (in case of 1 
concurrentConsumer)

- C2 exposes also two CXF services as producers of routes. Both of the 
two routes have one of those "internal" AMQ queues as their final 
destination. When we want to access their respective WSDL URL, the 
request hangs.

- We have an admin Web application monitoring C2 via JMX. The admin 
application hangs due to no response from C2's JMX services (although 
the C2 context starts up properly according to the logs).

- Nothing special can be seen in the logs. We examined the logs on DEBUG 
level (on Camel as well as on AMQ side) and nothing special could be seen.

- We went back to a rather base config. No transactions, no connection 
pools, no caching of consumers/producers. We have experimented with the 
prefetch (setting it to 1 or even 0) without success.

- In order to reach proper behavior again, Q1/Q2 (and maybe even the 
"internal queues of C2) have to be purged. Then C2 has be to be 
restarted again. After this procedure, message passing is back to normal.


Sorry for the long post, but I want to describe the problem as detailed 
as possible. Since we have been working on this now for days any help 
would be highly appreciated.


Thanks and best regards,


Marco




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