JMS Correlation ID in WSO2 ESB

You can retrieve original message id from the $header Synapse XPath expression and set it as the JMS_COORELATION_ID property in your message flow. That'll set as the correlation id of the underline JMS message.

<property name="JMS_COORELATION_ID" action="set" scope="axis2" expression="$header/wsa:MessageID" xmlns:wsa="http://www.w3.org/2005/08/addressing"/>

You'll need to define the Xpath appropriately to make sure that it address the both SOAP 1.1 and 1.2 messages.

Or else you can work around it in following method aslo.

1) In the request sequence we grab the message id:

 <property name="msgID" expression="get-property('MessageID')" />
2) In the response sequence we set the correlation id using:

 < roperty name="JMS_COORELATION_ID" expression="get-property('msgID')" scope="axis2" />

JMS Messagen Store and JMS Message Processor Behavior - WSO2 ESB - Part 3

So why did we meet the EVIL in the my last blog post? Why? yes that is the main reason behind this blog series!!

Now we have to take a deep breath before we dive into the WSO2 ESB and see why this has happened!!

If you carefully study the illustration shown in Figure 1, You will understand whats goes wrong ;)

Figure 1

Anyway, let me take some more time to explain little bit further.
Client sends message to Proxy. "Message Store" persist the message in the message store(JMS Queue). "Message Store" does not persist the message as it is in the JMS Queue. it serializes the message and other information into java serialized object and put it into JMS Queue.When "Message Processor" processes the message, it pulls Messages from JMS Queue and deserializes the java serialized object to further process.

So why did we encounter some exception and other problems in issue 1?
When Message Processor Pull the message from JMS Queue and try to deserialize, Deserilzation process fails since the fetched message is not Serialized by Message Store.

So is that possible to put message into Message Stores's "JMS Queue" ?? NO it is not possible!!!


So whats wrong with Issue 2?
Different JMS listener dose not know how to deserialize the message that fetched from JMS Queue(Message Store)!

Conclusion   

Messages that are put into "JMS Queue" by "Message Store" are can be read only by "Message Processor" and "Message Processor" only capable of understanding the messages that are put by "Message Store".





  

JMS Message Store and JMS Message Processor Behavior - WSO2 ESB - Part 1

I have seen lot of users of WSO2 ESB misunderstood the usage of "Message Stores" and "Message Processor" of the WSO2 ESB. In this Blog series, I will explain further about "Under the Hood" functionalists of the "Message Stores" and "Message Processor" to clear the doubts and myths behind those.

Lets take a very simple use case that i have illustrated bellow,

End of the day, Client is sending a message to Backend in this scenario. Nevertheless, under the hood we are persisting message in JMS queue using "Message Store" and sending it to backend using "Message Processor". This will make sure, we never loss any transaction even backend is fail.

When backend is up and running "Message Processor" send the persisted messages to Backend.

Lets try this concept using WSO2 ESB and ActiveMQ as a message broker. Please refer [1] to understand how to configure WSO2 ESB and ActiveMQ. 

As a Backend and Client, I am using WSO2 ESB SimpleStockQuoteService and Axis2 Client. Please note that, these are packed with WSO2 ESB by default. You can find more detail in [2].

Please refer to the Synapse configuration that has been given bellow which demonstrates the concept above. 

 Use the ant command as given bellow in order to invoke the proxy from client.

ant stockquote -Daddurl=http://localhost:9000/services/SimpleStockQuoteService -Dtrpurl=http://localhost:8280/services/MessageReciveProxy -Dmode=placeorder


As result you, can notice in the Backend, there will be transaction has happened. So underneath, our "MessageReciveProxy"  Proxy received the message and persisted in "JMSMessageStore"  Message Store. Thereafter, "SampleMessageForwardingProcessor"  Message Processor took the message from "JMSMessageStore" and send it to Backend for further process.


So far so good! Hmmmm

In my next post I will introduce the evil ;)





[1]http://docs.wso2.org/wiki/display/ESB470/Configure+with+ActiveMQ
[2]http://docs.wso2.org/wiki/display/ESB470/ESB+Samples+Setup#ESBSamplesSetup-StartingSampleBack-EndServices