JMS rollback in WsO2 ESB 4.7.0 - jms

Question

I have configured Apache ActiveMQ with transaction and CLIENT_ACKNOWLEDGE in WSO2 ESB 4.7.0. The axis2.xml config is :
<parameter name="transport.jms.SessionTransacted">true</parameter>
<parameter name="transport.jms.SessionAcknowledgement" locked="true">CLIENT_ACKNOWLEDGE</parameter>
I have a simple passthrough proxy with jms transport which passes the messages in the JMS queue to a jax-rs service. The proxy code is :
<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
name="MediaMoveQueue"
transports="jms"
startOnLoad="true"
trace="enable">
<description/>
<target>
<inSequence>
<property name="messageType" value="application/json" scope="axis2"/>
<property name="ContentType" value="application/json" scope="axis2"/>
<send receive="JmsRollbackSequence">
<endpoint>
<address uri="http://192.168.1.2:9766/RestMediaMove_1.0.0/services/rest_media_move_i_f/restmediamoveif/hello"/>
</endpoint>
</send>
<log level="custom">
<property name="In MediaMoveQueue JMSERROR"
expression="get-property('JMSERROR')"/>
</log>
<switch source="get-property('JMSERROR')">
<case regex="true">
<property name="SET_ROLLBACK_ONLY" value="true" scope="axis2"/>
<log level="custom">
<property name="In MediaMoveQueue Transaction Action"
value="Rollbacked"/>
</log>
</case>
<case regex="false">
<log level="custom">
<property name="In MediaMoveQueue Transaction Action"
value="Committed"/>
</log>
</case>
<default>
<property name="SET_ROLLBACK_ONLY" value="true" scope="axis2"/>
<log level="custom">
<property name="In MediaMoveQueue Transaction Action default"
value="Rollbacked"/>
</log>
</default>
</switch>
</inSequence>
<outSequence>
<log level="full">
<property name="test" value="IN outsequence"/>
</log>
<send/>
</outSequence>
</target>
<parameter name="transport.jms.ContentType">
<rules>
<jmsProperty>contentType</jmsProperty>
<default>application/json</default>
</rules>
</parameter>
</proxy>
The JmsRollbackSequence sequence receives the reply from the jax-rs service and depending on the reply success or failure returned, I would like to rollback the JMS transaction. But if I set the property in the JmsRollbackSequence it has absolutely no effect ( I tried it first before using the sequence shown below). The transaction is never rolled back. The rollback works only if the property is set in the inSequence. Here is the code for the JmsRollbackSequence :
<?xml version="1.0" encoding="UTF-8"?>
<sequence xmlns="http://ws.apache.org/ns/synapse" name="JmsRollbackSequence">
<property name="JMSERROR" value="true"/>
<log level="full">
<property name="test" value="IN JmsRollbackSequence"/>
</log>
</sequence>
So I tried to set up a property called JMSERROR in the JmsRollbackSequence and by reading it after the send mediator in the inSequence I thought I can roll back the transaction in the inSequence. But this does not work either. The switch case in inSequence is called before the property is set up in JmsRollbackSequence so when I read it it always returns null.
So my questions are :
1) Can we set
in a sequence? Why does it not work in JmsRollbackSequence?
2) As mediators are supposed to be called sequentially, why does the switch case in inSequence run before the JmsRollbackSequence has a chance to read the reply and set up the JMSERROR property?

Answer 1

"send" mediator is asynchronous : inSequence will continue his job and JMS transaction will be commited before the response arrive in your JmsRoolbackSequence.
use "callout" mediator for synchronous calls and create a faultSequence in your proxy to deal with errors and rollback your transaction :
<faultSequence>
<property name="SET_ROLLBACK_ONLY" value="true" scope="axis2"/>
</faultSequence>