Package org.apache.geode.management.membership

Class UniversalMembershipListenerAdapter

java.lang.Object
org.apache.geode.management.membership.UniversalMembershipListenerAdapter
All Implemented Interfaces:
MembershipListener
public abstract class UniversalMembershipListenerAdapter extends Object implements MembershipListener

The UniversalMembershipListenerAdapter is a wrapper for MembershipListener and ClientMembershipListener, providing a facade that makes both appear as a single MembershipListener . This includes adapting ClientMembershipListener events to appear as events for the MembershipListener.

UniversalMembershipListenerAdapter implements MembershipListener, exposing the callback in that interface as methods to be overridden by implementing classes.

An internal implementation of ClientMembershipListener is registered when this class is instantiated. This implementation creates a MembershipEvent and calls the corresponding MembershipListener public methods on UniversalMembershipListenerAdapter.The ClientMembershipEvents are wrapped to appear as MembershipEvents. In this way, both types of membership events appear as MembershipEvents.

Any CacheServer using the UniversalMembershipListenerAdapter will receive notifications of peer membership changes and client membership changes through a single listener.

Any cache client using the UniversalMembershipListenerAdapter would receive notifications of cache server connection changes. If that cache client also creates a connection to the GemFire DistributedSystem, then it will also register the adapter for membership events. But it wont be an automatic process. User needs to register the UniversalMembershipListenerAdapter with ManagementService to receive membership events. How to register UniversalMembershipListenerAdapter with ManagementService is explained below.

Subclasses of UniversalMembershipListenerAdapter may be registered as a MembershipListener using ManagementService.addMembershipListener(org.apache.geode.management.membership.MembershipListener) .It is best, however, to register the listener using registerMembershipListener(org.apache.geode.management.ManagementService) since this allows the adapter to prevent duplicate events for members that are both a peer member and a client.

Simply constructing the UniversalMembershipListenerAdapter results in the underlying ClientMembershipListener also being registered.

The following code illustrates how a CacheServer application would use UniversalMembershipListenerAdapter. The code in this example assumes that the class MyMembershipListenerImpl extends UniversalMembershipListenerAdapter: 

 
 public class MyMembershipListenerImpl extends UniversalMembershipListenerAdapter {
   public void memberCrashed(MembershipEvent event) {
     // customer code
   }
   public void memberLeft(MembershipEvent event) {
     // customer code
   }
   public void memberJoined(MembershipEvent event) {
     // customer code
   }
 }

  Cache cache = //Get hold of GemFire Cache instance
  ManagementService service = ManagementService.getExistingManagementService(cache);

  MyMembershipListenerImpl myListener = new MyMembershipListenerImpl();
  myListener.registerMembershipListener(service);
The callback on MyMembershipListenerImpl would then be invoked for all MembershipEvents and ClientMembershipEvents. The latter will appear to be MembershipEvents.

Similarly, the following code illustrates how a client application would use UniversalMembershipListenerAdapter, where MyMembershipListenerImpl is a subclass.Simply by constructing this subclass of UniversalMembershipListenerAdapter it is registering itself as a ClientMembershipListener: 

 
 new MyMembershipListenerImpl();
A client that also connects to the DistributedSystem could register with theManagementService as shown above.

It is recommended that subclasses register with the ManagementService using registerMembershipListener(org.apache.geode.management.ManagementService), as this will prevent duplicate events for members that are both clients and peer members.If duplicate events are acceptable, you may register subclasses using ManagementService#addMembershipListener.

Since:
GemFire 8.0

  • Field Details

    • DEFAULT_HISTORY_SIZE

      public static final int DEFAULT_HISTORY_SIZE
      Default number of historical events to track in order to avoid duplicate events for members that are both clients and peer members; value is 100.
      See Also:

    • membershipListener

      protected final MembershipListener membershipListener

  • Constructor Details

    • UniversalMembershipListenerAdapter

      public UniversalMembershipListenerAdapter()
      Constructs an instance of UniversalMembershipListenerAdapter.

    • UniversalMembershipListenerAdapter

      public UniversalMembershipListenerAdapter(int historySize)
      Constructs an instance of UniversalMembershipListenerAdapter.
      Parameters:
      historySize - number of historical events to track in order to avoid duplicate events for members that are both client and peer members; must a number between 10 and Integer.MAX_INT
      Throws:
      IllegalArgumentException - if historySize is less than 10

  • Method Details

    • registerMembershipListener

      public void registerMembershipListener(ManagementService service)
      Registers this adapter with the ManagementService. Registering in this way allows the adapter to ensure that callback will not be invoked twice for members that have a client connection and a peer connection. If you register with ManagementService.addMembershipListener(org.apache.geode.management.membership.MembershipListener) then duplicate events may occur for members that are both client and peer.
      Parameters:
      service - the ManagementService with which to register this adapter

    • unregisterMembershipListener

      public void unregisterMembershipListener(ManagementService service)
      Unregisters this adapter with the ManagementService. If registration is performed with registerMembershipListener(org.apache.geode.management.ManagementService) then this method must be used to successfully unregister the adapter.
      Parameters:
      service - the ManagementService with which to unregister this adapter

    • registerClientMembershipListener

      public void registerClientMembershipListener()
      Registers this adapter as a ClientMembershipListener. Registration is automatic when constructing this adapter, so this call is not necessary unless it was previously unregistered by calling unregisterClientMembershipListener().

    • unregisterClientMembershipListener

      public void unregisterClientMembershipListener()
      Unregisters this adapter as a ClientMembershipListener.
      See Also:

    • memberJoined

      public void memberJoined(MembershipEvent event)
      Invoked when a member has joined the distributed system. Also invoked when a client has connected to this process or when this process has connected to a CacheServer.
      Specified by:
      memberJoined in interface MembershipListener
      Parameters:
      event - the triggering event

    • memberLeft

      public void memberLeft(MembershipEvent event)
      Invoked when a member has gracefully left the distributed system. Also invoked when a client has gracefully disconnected from this process. or when this process has gracefully disconnected from a CacheServer.
      Specified by:
      memberLeft in interface MembershipListener
      Parameters:
      event - the triggering event

    • memberCrashed

      public void memberCrashed(MembershipEvent event)
      Invoked when a member has unexpectedly left the distributed system. Also invoked when a client has unexpectedly disconnected from this process or when this process has unexpectedly disconnected from a CacheServer.
      Specified by:
      memberCrashed in interface MembershipListener
      Parameters:
      event - the triggering event