request-reply router is not working - mule

Question

I am stuck up with a problem with the request-reply router in mule. I am using the mule release 3.4.0. The request-reply is used in a fork-join pattern , i followed this article on the blog site http://blogs.mulesoft.org/aggregation-with-mule-fork-and-join-pattern/.
<request-reply>
<all enableCorrelation="ALWAYS">
<vm:outbound-endpoint path="PathA"/>
<vm:outbound-endpoint path="PathB"/>
</all>
<vm:inbound-endpoint path="FinalResponse">
<message-properties-transformer>
<add-message-property key="MULE_CORRELATION_GROUP_SIZE" value="2" />
</message-properties-transformer>
<collection-aggregator />
</vm:inbound-endpoint>
</request-reply>
The issue that i face is the processor placed after the request-reply is not reached.In mule i see 2 responses been sent to the FinalResponse vm endpoint. I tried placing my own custom aggregator in place of the collection-aggregator. But this is not reached. I am not sure how i can debug this issue. Please note that i have 2 such request-reply routers in two flows. Can someone help on this.
Adding the mule configuration. For abbrevity attaching only the parent flow and one of the child flow
ParentFlow
<flow name="ParentFlow" doc:name="ParentFlow" tracking:enable-default-events="true">
<file:inbound-endpoint path="${SourceFilePath}"
connector-ref="ParentFlowInboundConnector"
responseTimeout="10000" tracking:enable-default-events="true">
<file:filename-regex-filter pattern="${REGEX}" caseSensitive="false"/>
</file:inbound-endpoint>
<object-to-string-transformer doc:name="Object to String"/>
<message-properties-transformer
doc:name="Message Properties">
<add-message-property key="Source_System" value="XXX" />
<add-message-property key="publisherName" value="YYY" />
<add-message-property key="FlowName" value="ZZZ"/>
</message-properties-transformer>
<!-- This would store the message in the db -->
<wire-tap>
<vm:outbound-endpoint path="PERSITENCE.OUT"/>
</wire-tap>
<request-reply>
<all doc:name="Move the message to all endpoints" enableCorrelation="ALWAYS">
<vm:outbound-endpoint path="PathA"/>
<vm:outbound-endpoint path="PathB"/>
<vm:outbound-endpoint path="PathC"/>
<vm:outbound-endpoint path="PathD"/>
</all>
<vm:inbound-endpoint path="Response">
<message-properties-transformer>
<add-message-property key="MULE_CORRELATION_GROUP_SIZE" value="4" />
</message-properties-transformer>
<collection-aggregator failOnTimeout="false" doc:name="Collection Aggregator" />
</vm:inbound-endpoint>
</request-reply>
<component class="ProcessorA" />
<component class="ProcessorB" />
<exception-strategy ref="Exception Strategy" doc:name="Reference Exception Strategy"/>
</flow>
Child Flow
<flow name="PathA" doc:name="PathA">
<vm:inbound-endpoint path="PathA" >
<vm:transaction action="ALWAYS_BEGIN"/>
</vm:inbound-endpoint>
<message-properties-transformer doc:name="Message Properties">
<add-message-property key="originalFilename_processing" value="#[message.inboundProperties.originalFilename]" />
</message-properties-transformer>
<message-properties-transformer doc:name="Message Properties">
<add-message-property key="directory" value="#[message.inboundProperties.directory]" />
</message-properties-transformer>
<message-properties-transformer doc:name="Message Properties">
<add-message-property key="Destination_System" value="XXX" />
</message-properties-transformer>
<file:outbound-endpoint path="${OutPathA}" connector-ref="FileConnector_1"
tracking:enable-default-events="true"/>
<!--Send email alerts -->
<all doc:name="All" >
<processor-chain>
<message-property-filter pattern="turnOffEmail=false" caseSensitive="true" doc:name="Message Property"/>
<custom-transformer class="com.XXX.YYY.ZZZ.VelocityTemplateResolver" doc:name="Java">
<spring:property name="flowName" value="PPPP"/>
</custom-transformer>
<smtp:outbound-endpoint host="${SMTP_HOSTNAME}" port="${SMTP_PORT}" user="${SMTP_USERNAME}" password="${SMTP_PASSWORD}" to="${TO_ADDRESS}" from="${FROM_ADDRESS}" subject="${MAIL_SUBJECT}" cc="${MAIL_CC_ADDRESS}" bcc="${MAIL_BCC_ADDRESS}" responseTimeout="10000" transformer-refs="emailVelocityMessageTransformer" tracking:enable-default-events="true"/>
</processor-chain>
<processor-chain>
<message-property-filter pattern="turnOffEmail=false" caseSensitive="true" doc:name="Message Property"/>
<custom-transformer class="com.XXX.YYY.ZZZ.VelocityTemplateResolver" doc:name="Java">
<spring:property name="flowName" value="FlowName"/>
</custom-transformer>
<smtp:outbound-endpoint host="${SMTP_HOSTNAME}" port="${SMTP_PORT}" user="${SMTP_USERNAME}" password="${SMTP_PASSWORD}" to="${MAIL_TO_ADDRESS}" from="${MAIL_FROM_ADDRESS}" subject="${MAIL_SUBJECT}" cc="${MAIL_CC_ADDRESS}" bcc="${BCC_ADDRESS}" responseTimeout="10000" transformer-refs="emailVelocityMessageTransformer" tracking:enable-default-events="true"/>
</processor-chain>
<processor-chain>
<message-property-filter pattern="turnOffEmail=false" caseSensitive="true" doc:name="Message Property"/>
<custom-transformer class="com.XXX.YYY.ZZZ.VelocityTemplateResolver" doc:name="Java">
<spring:property name="flowName" value="AAAA"/>
</custom-transformer>
<smtp:outbound-endpoint host="${SMTP_HOSTNAME}" port="${SMTP_PORT}" user="${SMTP_USERNAME}" password="${SMTP_PASSWORD}" to="${MAIL_TO_ADDRESS}" from="${MAIL_FROM_ADDRESS}" subject="${MAIL_SUBJECT}" cc="${MAIL_CC_ADDRESS}" bcc="${MAIL_BCC_ADDRESS}" responseTimeout="10000" transformer-refs="emailVelocityMessageTransformer" tracking:enable-default-events="true"/>
</processor-chain>
</all>
<rollback-exception-strategy doc:name="Rollback Exception Strategy" maxRedeliveryAttempts="${MAX_REDELIVERY_ATTEMPTS}" enableNotifications="false">
<logger message="==Rollback log ===" level="INFO" doc:name="Logger"/>
</rollback-exception-strategy>
</flow>

Answer 1

The most likely cause of the the problem is correlation ID.
You might want to inspect the correlation ID of the messages sent out to Path A and Path B. The message received on FinalResponse VM inbound endpoint needs to have the same correlation ID, otherwise it won't be accepted as a response to the messages previously sent. In other words the request-reply will NOT accept just anything in the inbound-endpoint but just the message matching the correlation ID of the posted on outbound-endpoint with the request-reply router.
You can set the custom correlation ID using this --
<set-property propertyName="MULE_CORRELATION_ID" value="some-correlation-id" />