Tuesday, 24 January 2012

Controlling Flows in Mule

After we saw how we can control routes in camel, we can now take a look at how to get the same behaviour in Mule. In mule instead of having routes we have flows. One thing to note is that a flow can be started or stopped but there is no notion of suspending and resuming flows. Apart from flows there are the deprecated Services which were use pre Mule 3. We should handle them as well and services do actually support pause and resume.

So what we will do is query the registry to get the service or flow. If it is a service then we can perform all 4 actions. If it is a flow, we can only perform stop and start. If we get a request for a pause, we will log a warning and perform a stop instead, whilst if we get a resume we will log a warning and perform a start.

The code of the FlowController is as follows:

One thing to note is that we are using the Lifecycle interface in order to control the flow. This actually can allow us to generalise our FlowController to start/stop not only flows and services but any component in the registry which implements the Lifecycle interface. This means that you will be able to control Connectors as well for example. For this we will make a minor change as follows:

Even though now our FlowController can do more than just control Flows and Services, I will still leave it called the FlowController since that is its main use, LifecycleController does not really cut it in my opinion ;).

As always you can browse the FlowController code and for usage examples you can look at the test implementation and test configuration.

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