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From Willem Jiang <willem.ji...@gmail.com>
Subject Re: Support for using JMS MessageID as CorrelationID
Date Fri, 16 Apr 2010 02:24:27 GMT
Hi Seumas,

Please see my comments in the mail.
Seumas Soltysik wrote:
> 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.
Yes, a simple config attribute could help us.

> 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.
> 
It's useless,
> 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.
> 
I recalled we make the JMSConduit simple and also want to support the 
messageIdPattern last summer, we changed the code like this and we don't 
support the async call for the messageIdPattern.

If you take a look at the first huge if condition checking again, you 
can see that.
I don't like the way to implement the listener per thread to the async 
call with the messageIdPattern by using the thread local, it looks a 
litter mass. How about a using a work queue to take the response 
receiving job ?

> Feedback on these issues is appreciated so that I can move ahead with modifying trunk/2.2.x/2.1.x.
> 
> Regards,
> Seumas
> 
> 
> 
> 
> 
Willem


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