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From "Marat Bedretdinov (JIRA)" <>
Subject [jira] Commented: (CAMEL-1461) A request route with a topic node incurs a 20 second wait and refers to the wrong MEP.
Date Sun, 05 Apr 2009 06:17:34 GMT


Marat Bedretdinov commented on CAMEL-1461:


Yes I did manage to get all of the tests to pass before I restarted this thread, but as you
said my use case is now quite cumbersome and I think it really does not have to be.

Please take a look at the patch attached. I think this will keep all happy. 

I also show how the use case you described could be implemented. That is when one wants to
have a request/reply over a queue and then also send a message (notification) over a topic
and then collect correlated acknowledgement message(s) that those notification have been received.

source app -> queue:request -> target app -> queue:reply -> source app
                     -> topic:notification

topic:notification -> notification subscriber app 1 -> queue:notificationAck
topic:notification -> notification subscriber app 2 -> queue:notificationAck
queue:notificationAck -> source app correlates ack using original request correlationID
or a unique selector

The usual use case for topics are one way messages, so if the user really wants to reply to
destination that came with a message received over a topic then the receiver should be ready
to accept more than one reply correlated on the same source message. Since a request/reply
pattern is 1 request 1 reply, then the reply destination embedded in the message that came
over a topic should really be decoupled from the destination used to receive a reply from
request/reply pattern.

> A request route with a topic node incurs a 20 second wait and refers to the wrong MEP.
> --------------------------------------------------------------------------------------
>                 Key: CAMEL-1461
>                 URL:
>             Project: Apache Camel
>          Issue Type: Bug
>          Components: camel-jms
>    Affects Versions: 1.6.0
>         Environment: ActiveMQ/Camel
>            Reporter: Michael Chen
>            Assignee: Claus Ibsen
>             Fix For: 2.0.0, 1.6.1
>         Attachments: CAMEL-1461-2009-04-05-01-58.patch
> If a route contains a node that publishes to a topic, the route is incorrectly suspended
for a default 20 seconds at the topic node.  Further, checks the MEP of the
original request Exchange and not the endpoint of the topic.
> For example, say I have a route built like this:
> {code}
> from("activemq:queue:request").
>   to("generate_news").
>   to("activemq:topic:news").
>   to("do_something_else");
> {code}
> The original request is expecting a reply. However, after the "news" is pumped into the
news topic, there is a default 20 second wait (requestTimeout).  This wait always results
in the exception: "The OUT message was not received within: 20000 millis on the exchange..."

> After reading the JmsProducer code, I changed the route to the following:
> {code}
> from("activemq:queue:request").
>   to("generate_news").
>   to("activemq:topic:news?exchangePattern=InOnly").
>   to("do_something_else");
> {code}
> This reveals the root of the bug, which is in the first few lines of method org.apache.camel.component.jms.JmsProducer.process(Exchange):
> {code}//
>     public void process(final Exchange exchange) {
>         final org.apache.camel.Message in = exchange.getIn();
>         if (exchange.getPattern().isOutCapable()) {
> {code}
> The above if statement checks the MEP of the original request's Exchange and not the
new endpoint of the news topic. This makes the above "?exchangePattern=InOnly" configuration
useless, because the original request MEP is InOut.  The result is that after that 20 second
time-out, the temporary queue for the original request has expired, so the whole request failed.
Note that the next node "do_something_else" is never reached due to the time-out exception.

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