Added notion of a general Store abstraction and wired it up in ClusterStore.
diff --git a/core/store/src/main/java/org/onlab/onos/store/cluster/impl/DistributedClusterStore.java b/core/store/src/main/java/org/onlab/onos/store/cluster/impl/DistributedClusterStore.java
index 77a28f5..004f807 100644
--- a/core/store/src/main/java/org/onlab/onos/store/cluster/impl/DistributedClusterStore.java
+++ b/core/store/src/main/java/org/onlab/onos/store/cluster/impl/DistributedClusterStore.java
@@ -12,7 +12,9 @@
 import org.apache.felix.scr.annotations.Component;
 import org.apache.felix.scr.annotations.Deactivate;
 import org.apache.felix.scr.annotations.Service;
+import org.onlab.onos.cluster.ClusterEvent;
 import org.onlab.onos.cluster.ClusterStore;
+import org.onlab.onos.cluster.ClusterStoreDelegate;
 import org.onlab.onos.cluster.ControllerNode;
 import org.onlab.onos.cluster.DefaultControllerNode;
 import org.onlab.onos.cluster.NodeId;
@@ -26,6 +28,8 @@
 import java.util.concurrent.ConcurrentHashMap;
 
 import static com.google.common.cache.CacheBuilder.newBuilder;
+import static org.onlab.onos.cluster.ClusterEvent.Type.INSTANCE_ACTIVATED;
+import static org.onlab.onos.cluster.ClusterEvent.Type.INSTANCE_DEACTIVATED;
 import static org.onlab.onos.cluster.ControllerNode.State;
 
 /**
@@ -33,14 +37,15 @@
  */
 @Component(immediate = true)
 @Service
-public class DistributedClusterStore extends AbstractDistributedStore
+public class DistributedClusterStore
+        extends AbstractDistributedStore<ClusterEvent, ClusterStoreDelegate>
         implements ClusterStore {
 
     private IMap<byte[], byte[]> rawNodes;
     private LoadingCache<NodeId, Optional<DefaultControllerNode>> nodes;
 
     private String listenerId;
-    private final MembershipListener listener = new InnerMembershipListener();
+    private final MembershipListener listener = new InternalMembershipListener();
     private final Map<NodeId, State> states = new ConcurrentHashMap<>();
 
     @Activate
@@ -106,11 +111,12 @@
     }
 
     // Adds a new node based on the specified member
-    private synchronized void addMember(Member member) {
+    private synchronized ControllerNode addMember(Member member) {
         DefaultControllerNode node = node(member);
         rawNodes.put(serialize(node.id()), serialize(node));
         nodes.put(node.id(), Optional.of(node));
         states.put(node.id(), State.ACTIVE);
+        return node;
     }
 
     // Creates a controller node descriptor from the Hazelcast member.
@@ -125,18 +131,20 @@
     }
 
     // Interceptor for membership events.
-    private class InnerMembershipListener implements MembershipListener {
+    private class InternalMembershipListener implements MembershipListener {
         @Override
         public void memberAdded(MembershipEvent membershipEvent) {
             log.info("Member {} added", membershipEvent.getMember());
-            addMember(membershipEvent.getMember());
+            ControllerNode node = addMember(membershipEvent.getMember());
+            notifyDelegate(new ClusterEvent(INSTANCE_ACTIVATED, node));
         }
 
         @Override
         public void memberRemoved(MembershipEvent membershipEvent) {
             log.info("Member {} removed", membershipEvent.getMember());
-            states.put(new NodeId(memberAddress(membershipEvent.getMember()).toString()),
-                       State.INACTIVE);
+            NodeId nodeId = new NodeId(memberAddress(membershipEvent.getMember()).toString());
+            states.put(nodeId, State.INACTIVE);
+            notifyDelegate(new ClusterEvent(INSTANCE_DEACTIVATED, getNode(nodeId)));
         }
 
         @Override