AMQP Egress Connector

First you need to specify a Connection Factory to connect to the AMQP Server. For this example let’s use Rabbit MQ and if you have not already installed Rabbit MQ, please follow the Installation Guide

In-order to use the transaction mode, you must first add the required resources in the project.xpml file. Right click on project.xpml file and from the context menu, select Resource Template as shown in below figure

After that from the shown dialog box, select RabbitMQ with Transaction template.

Next you need to specify the required parameters as shown below. It is mandatory to specify a bean prefix and for that you can specify any value. Apart from that you need to specify the host and port of the RabbitMQ server.

Now let’s see how we can send a message obtained from a remote RabbitMQ queue can be sent to multiple destination queues as an atomic operation through a transaction. First create the flow as shown below

As you can see, there is one AMQP Ingress Connector with a transaction manager specified, and Channel Transacted enabled (under Transaction tab in the property pane) and within the transaction scope there are two AMQP Egress Connectors to send the message to two destination queues. After sending the message to both queues, we are closing the transaction scope and completing the integration flow with a Successful Flow End component. If you run the project, you can see that the original message has been sent to both destination queues.

Now if we add an Exceptional Flow End element after the second AMQP Egress Connector, you can see that message flow completes with an exception while the transaction scope is still active. In this case, the original message is not sent to the either of destination queues and rolled back to the source queue.

This happens because when we specify the transaction manager to the AMQP Ingress Connector and include the Egress Connectors within the same transaction scope, all AMQP queueing/de-queuing operations are bounded with a singe transaction and if the message flow fails within the transaction scope (since the transaction scope is not closed), the transaction will be rolled back.

Now suppose you are getting a message from a non-transactional transport like HTTP. As shown in the below image, even in this case we can sent the message to multiple destination AMQP queues in a single transaction.

Although, in here you need to specify the transaction manager in the TransactionScopeStartElement as shown below.

Now if you modify the flow as below and run the project again, you can see that the message has not been sent to either of the AMQP destinations.

As an example in the above flow, the same transaction manager is specified for AMQP Ingress Connector, TransactionScopeStartElement and TransactionScopeEndElement. If any exception occurs within the transaction scope (A), the message will be rolled back to the original source queue and message will not be sent to any of the destination queues.

If any exception occurs within the transaction scope (B), then the message will be sent to the destination X, Y, but the message will not be sent to either of destinations P, Q.

When using the confirmation mode, you need to add a callback handler. In the project.xpml as mentioned previously, go to the "Resource Template" section and select RabbitMQ with Callback. Next, specify the required properties and save the pop-up modal. Now you can see that the required resources are added to the project.xpml file.

Now let’s create a simple flow as shown below

Now if you run this flow and send a message you will see an error message similar to below one

This means that the rabbit server has failed to find the destination queue and the message delivery has failed which results in a message flow failure.