Most recently, I had the need to create a bridge from Topics to Queues in order to create stateless services. The goal was to adopt a model where messages can be processed in parallel. Essentially, I wanted to configure the following (in the message broker):

While there are many other ways to do this, I wanted to experiment with ActiveMQ to support this setup. The following is how I configured it locally (in my dev box):

Use a Docker Image

I used an ActiveMQ docker image found here. It was pretty straightforward and was able to get it running after a few commands. Here is what I did to define a baseline (this is from the instructions in the link above):

  docker run --user root --rm -ti \
             -v /Users/alberto/workspace/docker/activemq/conf:/mnt/conf \
             -v /Users/alberto/workspace/docker/activemq/data:/mnt/data \
             rmohr/activemq:5.15.4-alpine /bin/sh

Notice the following:

• I created the /conf and /data directory in my dev box.
• I mounted these folders into the /mnt/* respective to my local box.
• As the end of this command, a shell will be started inside the docker container

Then, I had to do the following (within the docker container):

  chown activemq:activemq /mnt/conf
  chown activemq:activemq /mnt/data
  cp -a /opt/activemq/conf/* /mnt/conf/
  cp -a /opt/activemq/data/* /mnt/data/
  exit

Now, I have the configuration in my conf folder.

Configure ActiveMQ

Now that I have a mounted folder to the docker container (within the conf folder), I can edit the activemq.xml file so that the following is included in the virtualDestinations section:

1
2
3
4
5
6
7
8
9
10
11
  <destinationInterceptors>
    <virtualDestinationInterceptor>
      <virtualDestinations>
        <compositeTopic name="t.example.service.event">
          <forwardTo>
            <queue physicalName="q.example.service.review" />
          </forwardTo>
        </compositeTopic>
      </virtualDestinations>
    </virtualDestinationInterceptor>
  </destinationInterceptors>

The important lines here are the section where the compositeTopic is configured to forward messages to the queue. For a full example of the activemq.xml file, please find it here.

Test: Send A Message Forward

You can now go to the admin console at:

http://localhost:8161/admin/send.jsp

and send a message to the topic. You will see messages forwarded to the queues of your choice.