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How to Implement Dual Channel Scenario with RabbitMQ

This sample demonstrates how you can implement the request-reply messaging scenario (dual-channel scenario) using the RabbitMQ broker and WSO2 Micro Integrator.

As shown below, the OrderRequest proxy service in the Micro Integrator receives an HTTP request, which it publishes to a RabbitMQ queue. This message is consumed and processed by the OrderProcessing proxy service in the Micro Integrator, and the response is sent back to the client over HTTP.

Synapse configurations

See the instructions on how to build and run this example. 

<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
    name="OrderRequestService"
    transports="http https"
    startOnLoad="true">
   <description/>
   <target>
    <inSequence>
      <property name="rabbitmq.message.content.type"
                value="Content-Type"
                scope="axis2"/>
      <property name="TRANSPORT_HEADERS" scope="axis2" action="remove"/>
      <call>
          <endpoint>
            <address uri="rabbitmq:/order-request?rabbitmq.server.host.name=localhost&amp;rabbitmq.server.port=5672&amp;rabbitmq.server.user.name=guest&amp;rabbitmq.server.password=guest"/>
          </endpoint>
      </call>
      <respond/>
    </inSequence>
   </target>
</proxy>

<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
    name="OrderProcessingService"
    transports="rabbitmq"
    startOnLoad="true">
   <target>
    <inSequence>
      <call>
        <endpoint xmlns="http://ws.apache.org/ns/synapse">
          <http method="POST" uri-template="http://localhost:8290/orders"/>
        </endpoint>
      </call>
      <log level="full">
          <property name="Info" value="Your order has been placed successfully."/>
      </log>
      <respond/>
    </inSequence>
    <faultSequence>
      <payloadFactory media-type="xml">
          <format>
            <Error>$1</Error>
          </format>
          <args>
            <arg evaluator="xml" expression="get-property('ERROR_MESSAGE')"/>
          </args>
      </payloadFactory>
      <respond/>
    </faultSequence>
   </target>
   <parameter name="rabbitmq.queue.name">order-request</parameter>
   <parameter name="rabbitmq.connection.factory">AMQPConnectionFactory</parameter>
</proxy>

We can use the below synapse configurations to act as the mock backend called by the OrderProcessingService proxy service.

<?xml version="1.0" encoding="UTF-8"?>
<api context="/orders" name="mockOrdersBackend" xmlns="http://ws.apache.org/ns/synapse">
  <resource methods="POST">
    <inSequence>
      <property name="messageType" value="application/json" scope="axis2"/>
      <payloadFactory media-type="json">
        <format>{"message":"Order created"}</format>
          <args/>
      </payloadFactory>
      <respond/>
    </inSequence>
    <faultSequence>
      <payloadFactory media-type="json">
        <format>{"error":"Error processing order"}</format>
        <args/>
      </payloadFactory>
      <respond/>
    </faultSequence>
  </resource>
</api>

Build and run

  1. Launch Visual Studio Code with the Micro Integrator for VS Code extension (MI for VS Code) installed.

    Info

    Follow the Install Micro Integrator for VS Code documentation for a complete installation guide.

  2. Create an integration project.

  3. Create the proxy service with the configurations given above.
  4. Enable the RabbitMQ sender and receiver in the Micro-Integrator from the deployment.toml. Refer the configuring RabbitMQ documentation for more information.
  5. Deploy the artifacts in your Micro Integrator.
  6. Make sure you have a RabbitMQ broker instance running.

  7. Send a message to the Order Request Proxy Service with the following payload. 

    {   "orderId": "1242",
"orderQty": 43,
"orderDate": "2020/07/22"
}