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From Christian Schneider <ch...@die-schneider.net>
Subject Re: Support for using JMS MessageID as CorrelationID
Date Fri, 16 Apr 2010 07:22:49 GMT
Hi Seumas,

I also would prefer a property to activate the message id pattern. So I 
think we should use the same property on trunk and the branches.
I really donĀ“t like how the code on the trunk developed recently. On 
2.2.x it was quite understandable while I must say I am not sure I 
completely understand how the code on trunk works. We should try to 
reduce the complexity while keeping the necessary new features. Perhaps 
we should create a requirements and design document for the jms 
transport that describes what features we need. Alternatively well 
documented test could also achieve the same effect.

Apart from this if we can agree on a new property for message id pattern 
for trunk and branches we should add the feature to the branches quite 
fast as it is really important. Besides the property we should also 
agree on when the message id pattern will be active. Also see the 
discussion on the camel jira about this:
https://issues.apache.org/activemq/browse/CAMEL-2249

For example I think even if the message id property is true the server 
part should honor a correlation id given to it by the client. I think 
the code already does this but we should agree if this is the desired 
behaviour.

Greetings

Christian


Am 15.04.2010 19:46, schrieb Seumas Soltysik:
> I am trying to get support for using the JMS MessageID as the JMS CorrelationID as specified
in https://issues.apache.org/jira/browse/CXF-2760 . After putting some work/thought into this
issue, I became aware that this feature is available on the trunk but was not back-merged
to the 2.1.x and 2.2.x branches. I am in the process of trying take what is done on trunk
implement something similar on 2.1 and 2.2. However I have a  couple of issues with the implementation
on trunk that I want to sort out before back-porting.
>
> 1)There is no attribute in the clientConfig schema to specify that the user wants to
use the MessageID in lieu of the CorrelationID. Currently the logic for deciding whether to
use the MessageID instead of a generated CorrelationID looks like this:
>
>              } else if (!jmsConfig.isSetConduitSelectorPrefix()
>                         &&  (exchange.isSynchronous() || exchange.isOneWay())
>                         &&  (!jmsConfig.isSetUseConduitIdSelector()
>                             || !jmsConfig.isUseConduitIdSelector())) {
>                  messageIdPattern = true;
>
> This is quite a bit of mumbo-jumbo which could be sorted out by specifying a config attribute.
>
> 2)There is a bit of code which seem left over from a previous implementation that has
no value:
>
>              if (exchange.isSynchronous()) {
>                  synchronized (exchange) {
>                      exchange.put(CORRELATED, Boolean.TRUE);
>                      exchange.notifyAll();
>                  }
>              }
>
> I don't see the current purpose of this as I don't see any code which has another thread
waiting on the exchange mutex.
>
> 3)The biggest issue with the current implementation on the trunk is the fact that using
the MessageID as CorrelationID is not supported for asynchronous calls. I don't know if this
was purposeful or not but the MessageID as CorrelationID paradigm is only implemented for
synchronous calls. Here is the source of the problem:
>
>          if (!exchange.isOneWay()) {
>              synchronized (exchange) {
>                  jmsTemplate.send(jmsConfig.getTargetDestination(), messageCreator);
>                  if (messageIdPattern) {
>                      correlationId = messageCreator.getMessageID();
>                  }
>                  headers.setJMSMessageID(messageCreator.getMessageID());
>
>                  final String messageSelector = "JMSCorrelationID = '" + correlationId
+ "'";
>                  if (exchange.isSynchronous()) {
>                      javax.jms.Message replyMessage = jmsTemplate.receiveSelected(replyToDestination,
>                                                                                   messageSelector);
>                      if (replyMessage == null) {
>                          throw new RuntimeException("Timeout receiving message with correlationId
"
>                                                     + correlationId);
>                      } else {
>                          doReplyMessage(exchange, replyMessage);
>                      }
>                  }
>              }
>
> In this situation the MessageID is never put into the correlationMap for future correlation
in onMessage(). Furthermore if the call is async, there is no JMSListener set up to receive
the reply using a selector which selects for the CorrrelationID equal to the MessageID. So
the JMSConduit will never receive the async callback. In order to support the async scenario,
the JMSListener needs to dynamically set the MessageSelector after the message is sent and
the MessageID is available. Furthermore, in a multi-threaded environment, there has to be
one of these listeners per thread so that threads don't modify the same message selector when
making concurrent calls.
>
> Feedback on these issues is appreciated so that I can move ahead with modifying trunk/2.2.x/2.1.x.
>
> Regards,
> Seumas
>
>
>
>
>
>    


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