如何使OSGI EventAdmin处理多个线程中的事件

Question

I am developing OSGI project. There are lots of services uses event admin, sending and handling events. And it seems that event admin handles events in a single thread. When a handleEvent function is activated, any other handle event function wont starts until running handleEvent function exits. I tested it Thread.sleep function.

I wonder if there are any configuration or parameter to make event admin to handle events in a multi-threaded fashion.

I am using eclipse neon 3 and equinox comes with it.

Answer 1

This depends on the event admin impl you use. For felix eventadmin the default is to use 20 threads and it is configureable.

You also should use eventAdmin.postEvent to ensure async delivery.

Answer 2

The spec provides leeway in the number of threads used. However, there is one guarantee that can be costly. Events must be delivered in order to a given handler. This constraints parallel delivery. You can register a service property event.delivery=async.unordered that will remove this constrain for a handler and allows the Event Admin more leeway in delivering events.

I find it rather hard to believe that the Equinox version would use only one thread ...

To learn more about Event Admin, read the tutorial OSGi Event Admin – Publish & Subscribe