RabbitMQ AMQP Transport

AMQP is a wire-level messaging protocol that describes the format of the data that is sent across the network. If a system or application can read and write AMQP, it can exchange messages with any other system or application that understands AMQP, regardless of the implementation language.

The RabbitMQ AMQP transport is implemented using the RabbitMQ Java Client. It allows you to send or receive AMQP messages by directly calling an AMQP broker (RabbitMQ). 

The following diagram illustrates a scenario where the ESB Profile of WSO2 Enterprise Integrator (WSO2 EI) uses the RabbitMQ AMQP transport to exchange messages between RabbitMQ Java clients by calling a RabbitMQ broker.

Configuring the RabbitMQ AMQP transport

1. Open <EI_HOME>/conf/axis2/axis2.xml for editing.

2. In the transport listeners section, add the following RabbitMQ transport listener, replacing the values with your host, port, username, and password to connect to the AMQP broker. 

   <transportReceiver name="rabbitmq" class="org.apache.axis2.transport.rabbitmq.RabbitMQListener">
      <parameter name="AMQPConnectionFactory" locked="false">
         <parameter name="rabbitmq.server.host.name" locked="false">192.168.0.3</parameter>
         <parameter name="rabbitmq.server.port" locked="false">5672</parameter>
         <parameter name="rabbitmq.server.user.name" locked="false">user</parameter>
         <parameter name="rabbitmq.server.password" locked="false">abc123</parameter>
      </parameter>
   </transportReceiver>

   As an optional step, you can create multiple connection factories if you want this listener to connect to multiple brokers.

3. In the transport senders section, add the following RabbitMQ transport sender, which will be used for sending AMQP messages to a queue:

   <transportSender name="rabbitmq" class="org.apache.axis2.transport.rabbitmq.RabbitMQSender"/>

4. Start WSO2 EI.

RabbitMQ AMQP transport parameters

Following are details on the listener parameters you can set:

Following are details on the sender parameters you can set:

For the rabbitmq.server , properties refer to the server on which RabbitMQ is running.

Connection recovery in RabbitMQ

In case of a network failure or broker shutdown, the WSO2 EI server will try to recreate the connection. The following parameters need to be configured in the transport listener to enable connection recovery in RabbitMQ.

<parameter name="rabbitmq.connection.retry.interval" locked="false">10000</parameter>
<parameter name="rabbitmq.connection.retry.count" locked="false">5</parameter>   

If the parameters specified above are set, the WSO2 EI server will retry 5 times with 10000 ms time intervals to reconnect when the connection is lost. If reconnecting also fails, WSO2 EI will terminate the connection. If you do not specify values for the above parameters, WSO2 EI uses 30000ms as the default retry interval and 3 as the default retry count.

Optionally, you can configure the following parameter in the listener: 

<parameter name="rabbitmq.server.retry.interval" locked="false">10000</parameter>

The parameter specified above sets the retry interval with which the RabbitMQ client tries to reconnect. Generally having this value less than the value specified as rabbitmq.connection.retry.interval will help synchronize the reconnection of WSO2 EI and the RabbitMQ client.

SSL enabled RabbitMQ transport

To enable SSL support in RabbitMQ, you need to configure the transport listener with parameters required to enable SSL, as well as the parameters that provide information related to keystores and truststores.

Following is a sample SSL-enabled transport listener configuration:

<transportReceiver name="rabbitmq" class="org.apache.axis2.transport.rabbitmq.RabbitMQListener">					
 <parameter name="AMQPConnectionFactoryKS" locked="false">
   <parameter name="rabbitmq.server.host.name" locked="false">localhost</parameter>
   <parameter name="rabbitmq.server.port" locked="false">5671</parameter>
   <parameter name="rabbitmq.server.user.name" locked="false"></parameter>
   <parameter name="rabbitmq.server.password" locked="false"></parameter>
   <parameter name="rabbitmq.connection.retry.interval" locked="false">10000</parameter>
   <parameter name="rabbitmq.connection.retry.count" locked="false">5</parameter>
   <parameter name="rabbitmq.connection.ssl.enabled" locked="false">true</parameter>
   <parameter name="rabbitmq.connection.ssl.version" locked="false">SSL</parameter>
   <parameter name="rabbitmq.connection.ssl.keystore.location" locked="false">../client/keycert.p12</parameter>
   <parameter name="rabbitmq.connection.ssl.keystore.type" locked="false">PKCS12</parameter>
   <parameter name="rabbitmq.connection.ssl.keystore.password" locked="false">MySecretPassword</parameter>
   <parameter name="rabbitmq.connection.ssl.truststore.location" locked="false">ssl/rabbitstore</parameter>
   <parameter name="rabbitmq.connection.ssl.truststore.type" locked="false">JKS</parameter>
   <parameter name="rabbitmq.connection.ssl.truststore.password" locked="false">rabbitstore</parameter>
 </parameter> 
</transportReceiver>

Configuring parameters that provide information related to keystores and truststores can be optional based on your broker configuration.

For example, if fail_if_no_peer_cert is set to false in the RabbitMQ broker configuration, then you only need to specify <parameter name="rabbitmq.connection.ssl.enabled" locked="false">true</parameter>. Additionally, you can also set <parameter name="rabbitmq.connection.ssl.version" locked="false">true</parameter> parameter to specify the SSL version. If fail_if_no_peer_cert is set to true, you need to provide keystore and truststore information.

Following is a sample broker configuration where fail_if_no_peer_cert is set to false:

{ssl_options, [{cacertfile,"/path/to/testca/cacert.pem"},
               {certfile,"/path/to/server/cert.pem"},
               {keyfile,"/path/to/server/key.pem"},
               {verify,verify_peer},
               {fail_if_no_peer_cert,false}]} 	

The same parameter names are applicable for transport sender configurations.

Higher Throughput of Message Delivery to RabbitMQ

For increased performance and higher throughput in message delivery, configure the transport sender as follows:

<transportSender name="rabbitmq" class="org.apache.axis2.transport.rabbitmq.RabbitMQSender">
   <parameter name="CachedRabbitMQConnectionFactory" locked="false"> 
     <parameter name="rabbitmq.server.host.name" locked="false">localhost</parameter> 
     <parameter name="rabbitmq.server.port" locked="false">5672</parameter> 
     <parameter name="rabbitmq.server.user.name" locked="false">user</parameter> 
     <parameter name="rabbitmq.server.password" locked="false">abc123</parameter> 
   </parameter> 
</transportSender>

Creating the RabbitMQ proxy service

Following is a sample RabbitMQ proxy service named AMQPProxy, which consumes AMQP messages from one RabbitMQ broker and publishes them to another:

<proxy xmlns="http://ws.apache.org/ns/synapse" name="AMQPProxy" transports="rabbitmq" statistics="disable" trace="disable" startOnLoad="true">
   <target>
      <inSequence>
         <log level="full"/>
         <property name="OUT_ONLY" value="true"/>
         <property name="FORCE_SC_ACCEPTED" value="true" scope="axis2"/>
      </inSequence>
      <endpoint>
         <address
         uri="rabbitmq:/AMQPProxy?rabbitmq.server.host.name=192.168.0.3&rabbitmq.server.port=5672&rabbitmq.server.user.name=user&rabbitmq.server.password=abc123&rabbitmq.queue.name=queue2&rabbitmq.exchange.name=exchange2"/>
      </endpoint>
   </target>
   <parameter name="rabbitmq.queue.name">queue1</parameter>
   <parameter name="rabbitmq.exchange.name">exchange1</parameter>
   <parameter name="rabbitmq.connection.factory">AMQPConnectionFactory</parameter>
   <description></description>
</proxy>

Note the following:

• The transport key name is rabbitmq. You need to specify this key name in the transports parameter (ie., transports="rabbitmq").
• The proxy is defined as OUT_ONLY, because it does not expect a response from the endpoint.
• The endpoint specifies where the messages will be published. The URI prefix is rabbbitmq so that the RabbitMQ AMQP transport will be used to publish the message. Be sure to specify the rest of the parameters in the URI as shown in the sample proxy service above. (NOTE: if you are configuring the URI through the management console instead of entering the configuration directly in the configuration file, you must encode the ampersands in the URI as "&" instead of "&".) If you do not know which RabbitMQ exchange to use, leave the value blank to use the default exchange.
• The rabbitmq.queue.name parameter specifies the queue on which the proxy service listens and consumes messages. If you do not specify a name for this parameter, the name of the proxy service will be used as the queue name.
•  The rabbitmq.exchange.name parameter specifies the RabbitMQ exchange to which the queue is bound. If you do not want to use a specific exchange, leave this value blank to use the default exchange.
• The rabbitmq.connection.factory parameter specifies the listener that listens on the queue and consumes messages. In this example, the connection factory is set to the name of the listener we created earlier (ie., AMQPConnectionFactory).

You can modify the sample proxy service above to handle scenarios where you only want to receive AMQP messages but need to send messages in a different format, or you want to receive messages in a different format and send only AMQP messages. You can also modify the proxy service to work with a different transport. For example, you can create a proxy that uses the RabbitMQ AMQP transport to listen to messages and then sends them over HTTP or JMS.

Sample java clients

This section describes the sample Java clients that you can use to send and receive AMQP messages. These clients can be used to test the scenario where the Sender publishes a message to a RabbitMQ AMQP queue, which is consumed by WSO2 EI and published to another queue, which in turn is consumed by the Receiver. When you run these clients, the Receiver will get the messages sent by the Sender, confirming that you have correctly configured the RabbitMQ AMQP transport.

AMQP sender

The following Java client sends SOAP XML messages to a RabbitMQ queue:

ConnectionFactory factory = new ConnectionFactory();
factory.setHost(host);
factory.setUsername(username);
factory.setPassword(password);
factory.setPort(port);
Connection connection = factory.newConnection();
Channel channel = connection.createChannel();
channel.queueDeclare(queueName, false, false, false, null);
channel.exchangeDeclare(exchangeName, "direct", true);
channel.queueBind(queueName, exchangeName, routingKey);

// The message to be sent
String message = "<soapenv:Envelope
                  xmlns:soapenv=\"http://schemas.xmlsoap.org/soap/envelope">\n" +  
                 "<soapenv:Header/>\n" +
                 "<soapenv:Body>\n" +
                 "  <p:greet xmlns:p=\"http://greet.service.kishanthan.org\">\n" + 
                 "     <in>" + name + "</in>\n" +
                 "  </p:greet>\n" +
                 "</soapenv:Body>\n" +
                 "</soapenv:Envelope>";

// Populate the AMQP message properties
AMQP.BasicProperties.Builder builder = new
AMQP.BasicProperties().builder();
builder.messageId(messageID);
builder.contentType("text/xml");
builder.replyTo(replyToAddress);
builder.correlationId(correlationId);
builder.contentEncoding(contentEncoding);

// Custom user properties
Map<String, Object> headers = new HashMap<String, Object>();
headers.put("SOAP_ACTION", "greet");
builder.headers(headers);

// Publish the message to exchange
channel.basicPublish(exchangeName, queueName, builder.build(), message.getBytes());

This client was tested with SOAP messages sent and consumed from AMQP broker queues with the content type “text/xml”. When specifying the queue name for publishing messages, be sure to specify the same queue where the RabbitMQ transport listener is listening.

AMQP receiver

When specifying the queue name for consuming messages, be sure to specify the same queue configured in the proxy service endpoint.

ConnectionFactory factory = new ConnectionFactory();
factory.setHost(hostName);
factory.setUsername(userName);
factory.setPassword(password);
factory.setPort(port);
Connection connection = factory.newConnection();
Channel channel = connection.createChannel();
channel.queueDeclare(queueName, false, false, false, null);
channel.exchangeDeclare(exchangeName, "direct", true);
channel.queueBind(queueName, exchangeName, routingKey);

// Create the consumer
QueueingConsumer consumer = new QueueingConsumer(channel);
channel.basicConsume(queueName, true, consumer);

// Start consuming messages
while (true) {
   QueueingConsumer.Delivery delivery = consumer.nextDelivery();
   String message = new String(delivery.getBody());
}

For more information on the implementation details of common RabbitMQ use cases, see the following topics:

• WSO2 EI as a RabbitMQ Message Consumer
• WSO2 EI as a RabbitMQ Message Producer
• Remote Procedure Call(RPC) with RabbitMQ