WSO2 ESB Message Flow

WSO2 ESB is a lightweight open source and high performing ESB. It is built on Synpase, which acts as the mediation engine.

This blog post describes the message flow of ESB at the synapse level from the client to backend and then backend to client.

To trace the message flow we can deploy a proxy service and invoke that,

<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
       name="TestProxy"
       startOnLoad="true"
       statistics="disable"
       trace="disable"
       transports="https,http">
   <target>
      <inSequence>
         <log/>
         <send>
            <endpoint>
               <address uri="http://www.mocky.io/v2/5924085b100000771e003629"/>
            </endpoint>
         </send>
      </inSequence>
   </target>
   <description/>
</proxy>
           

When a request comes from the client side, at the synapse level, it first hits the receive method in ProxyServiceMessageReceiver. This is the message flow in the request flow,

In-Flow

               
org.apache.synapse.core.axis2.ProxyServiceMessageReceiver.receive
at this level having the axis2 message context

org.apache.synapse.core.axis2.MessageContextCreatorForAxis2.getSynapseMessageContext 
get the synapse message context out of it

org.apache.synapse.core.axis2.ProxyService.registerFaultHandler
fault handler is registered for the proxy service

org.apache.synapse.mediators.base.SequenceMediator.mediate
call the mediate method in the in-sequence

org.apache.synapse.mediator.AbstractListMediator.mediate
iterates through mediators in the in-sequence

org.apache.synapse.mediators.builtin.SendMediator.mediate

org.apache.synapse.endpoints.AddressEndpoint.send

org.apache.synapse.core.axis2.Axis2Sender.sendOn

org.apache.synapse.core.axis2.Axis2FlexibleMEPClient.send

Out-Flow

 

org.apache.synapse.core.axis2.SynapseCallbackReceiver.receive

org.apache.synapse.core.axis2.SynapseCallbackReceiver.handleMessage

org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage

org.apache.synapse.mediators.base.SequenceMediator.mediate()
call the mediate method in the out-sequence

org.apache.synapse.mediators.AbstractListMediator.mediate()
iterates through mediators in the out-sequence

org.apache.synapse.mediators.builtin.SendMediator.mediate()

org.apache.synapse.core.axis2.Axis2Sender.sendBack