Inject new/existing Service<org.jboss.as.clustering.api.GroupMembershipListener>

[vithun.v]

For listening group membership changes, Paul Ferraro suggested the following approach

Quoting to thread https://community.jboss.org/message/715940#715940  ,

2. Create a custom subsystem that either creates a new, or injects an existing, Service<org.jboss.as.clustering.api.GroupMembershipListener & org.jboss.as.clustering.api.GroupRpcDispatcher>.  This object returned by this service is a slimmed down, slightly tidier version of HAPartition.

How do we actually do that?

I already went through https://docs.jboss.org/author/display/AS71/Extending+JBoss+AS+7 , I just wnated to know, hw do we inject something? and how do we do that in this case?

 ..... either creates a new, or injects an existing, Service<org.jboss.as.clustering.api.GroupMembershipListener & org.jboss.as.clustering.api.GroupRpcDispatcher>....... 

[pferraro]

Your custom service - the one that want to listen to cluster membership changes - should add a dependency on the relevant GroupMembershipNotifier service.

e.g.

{code}public class MyService implements Service<Foo>, GroupMembershipListener {
   private final Value<GroupMembershipNotifier> notifier;
   public MyService(Value<GroupMembershipNotifier> notifier) {
      this.notifier = notifier;
   }
   @Override
   public void start(StartContext context) {
     this.notifier.getValue().registerGroupMembershipListener(this);
   }
   @Override
   public void stop(StopContext context) {
     this.notifier.getValue().unregisterGroupMembershipListener(this);
  }
   @Override
   public void membershipChanged(...) {
      // ...
   }
}{code}

In your subsystem's add operation handler, where you'll want to install your custom service, you'll do something like:

{code}InjectedValue<GroupMembershipNotifier> notifier = new InjectedValue<GroupMembershipNotifier>();
ServiceName name = ...;
MyService service = new MyService(notifier);
context.getServiceTarget().addService(name, service).addDependency(ServiceName.JBOSS.append("cluster", "insert-cluster-name-here"), GroupMembershipNotifier.class, notifier).install();{code}

The module providing this extension will need a dependency on the org.jboss.as.clustering.api module.