If you ever need to do some data processing outside the scope of the web’s request/response, look no further than the Message Bus. It’s conceptually similar to Java Messaging Service (JMS) Topics, but sacrifices transactional, reliable delivery capabilities, making it much lighter-weight. Liferay Portal uses Message Bus all over the place:
- Search engine integration
- Email subscriptions
- Document Library processing
- Background tasks
- Cluster-wide request execution
- Clustered cache replication
You can use it too! Here are some of Message Bus’s most important features:
- publish/subscribe messaging
- request queuing and throttling
- flow control
- multi-thread message processing
There are also tools, such as the Java SE’s JConsole, that can monitor Message Bus activities.
The Message Bus topics are covered in these tutorials:
Since all messages are sent to and received at destinations, messaging destinations is worth exploring first.