Added notion of a general Store abstraction and wired it up in ClusterStore.

+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>org.onlab.onos</groupId>
+        <artifactId>onos-apps</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../pom.xml</relativePath>
+    </parent>
+
+    <artifactId>onos-app-foo</artifactId>
+    <packaging>bundle</packaging>
+
+    <description>ONOS application for miscellaneous experiments</description>
+
+</project>

+package org.onlab.onos.foo;
+
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.onlab.onos.cluster.ClusterEvent;
+import org.onlab.onos.cluster.ClusterEventListener;
+import org.onlab.onos.cluster.ClusterService;
+import org.slf4j.Logger;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Playground app component.
+ */
+@Component(immediate = true)
+public class FooComponent {
+
+    private final Logger log = getLogger(getClass());
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected ClusterService clusterService;
+
+    private ClusterEventListener clusterListener = new InnerClusterListener();
+
+    @Activate
+    public void activate() {
+        clusterService.addListener(clusterListener);
+        log.info("Started");
+    }
+
+    @Deactivate
+    public void deactivate() {
+        clusterService.removeListener(clusterListener);
+        log.info("Stopped");
+    }
+
+    private class InnerClusterListener implements ClusterEventListener {
+        @Override
+        public void event(ClusterEvent event) {
+            log.info("WOOOOT! {}", event);
+        }
+    }
+}
+
+

@@ -19,6 +19,7 @@
     <modules>
         <module>tvue</module>
         <module>fwd</module>
+        <module>foo</module>
     </modules>
 
     <properties>

 package org.onlab.onos.cluster;
 
+import org.onlab.onos.store.Store;
+
 import java.util.Set;
 
 /**
  * Manages inventory of controller cluster nodes; not intended for direct use.
  */
-public interface ClusterStore {
+public interface ClusterStore extends Store<ClusterEvent, ClusterStoreDelegate> {
 
     /**
      * Returns the local controller node.

+package org.onlab.onos.cluster;
+
+import org.onlab.onos.store.StoreDelegate;
+
+/**
+ * Cluster store delegate abstraction.
+ */
+public interface ClusterStoreDelegate extends StoreDelegate<ClusterEvent> {
+}

+package org.onlab.onos.cluster;
+
+import org.onlab.onos.store.StoreDelegate;
+
+/**
+ * Mastership store delegate abstraction.
+ */
+public interface MastershipStoreDelegate extends StoreDelegate<MastershipEvent> {
+}

+package org.onlab.onos.net.device;
+
+import org.onlab.onos.store.StoreDelegate;
+
+/**
+ * Infrastructure device store delegate abstraction.
+ */
+public interface DeviceStoreDelegate extends StoreDelegate<DeviceEvent> {
+}

+package org.onlab.onos.store;
+
+import org.onlab.onos.event.Event;
+
+/**
+ * Base implementation of a store.
+ */
+public class AbstractStore<E extends Event, D extends StoreDelegate<E>>
+        implements Store<E, D> {
+
+    protected D delegate;
+
+    @Override
+    public void setDelegate(D delegate) {
+        this.delegate = delegate;
+    }
+
+    @Override
+    public D getDelegate() {
+        return delegate;
+    }
+
+    /**
+     * Notifies the delegate with the specified event.
+     *
+     * @param event event to delegate
+     */
+    protected void notifyDelegate(E event) {
+        if (delegate != null) {
+            delegate.notify(event);
+        }
+    }
+}

+package org.onlab.onos.store;
+
+import org.onlab.onos.event.Event;
+
+/**
+ * Abstraction of a entity capable of storing and/or distributing information
+ * across a cluster.
+ */
+public interface Store<E extends Event, D extends StoreDelegate<E>> {
+
+    /**
+     * Sets the delegate on the store.
+     *
+     * @param delegate new store delegate
+     */
+    void setDelegate(D delegate);
+
+    /**
+     * Get the current store delegate.
+     *
+     * @return store delegate
+     */
+    D getDelegate();
+
+}

+package org.onlab.onos.store;
+
+import org.onlab.onos.event.Event;
+
+/**
+ * Entity associated with a store and capable of receiving notifications of
+ * events within the store.
+ */
+public interface StoreDelegate<E extends Event> {
+
+    void notify(E event);
+
+}

+/**
+ * Abstractions for creating and interacting with distributed stores.
+ */
+package org.onlab.onos.store;
\ No newline at end of file

@@ -11,6 +11,7 @@ import org.onlab.onos.cluster.ClusterEvent;
 import org.onlab.onos.cluster.ClusterEventListener;
 import org.onlab.onos.cluster.ClusterService;
 import org.onlab.onos.cluster.ClusterStore;
+import org.onlab.onos.cluster.ClusterStoreDelegate;
 import org.onlab.onos.cluster.ControllerNode;
 import org.onlab.onos.cluster.NodeId;
 import org.onlab.onos.event.AbstractListenerRegistry;
@@ -32,6 +33,8 @@ public class ClusterManager implements ClusterService, ClusterAdminService {
     public static final String INSTANCE_ID_NULL = "Instance ID cannot be null";
     private final Logger log = getLogger(getClass());
 
+    private ClusterStoreDelegate delegate = new InternalStoreDelegate();
+
     protected final AbstractListenerRegistry<ClusterEvent, ClusterEventListener>
             listenerRegistry = new AbstractListenerRegistry<>();
 
@@ -43,6 +46,7 @@ public class ClusterManager implements ClusterService, ClusterAdminService {
 
     @Activate
     public void activate() {
+        store.setDelegate(delegate);
         eventDispatcher.addSink(ClusterEvent.class, listenerRegistry);
         log.info("Started");
     }
@@ -90,4 +94,13 @@ public class ClusterManager implements ClusterService, ClusterAdminService {
     public void removeListener(ClusterEventListener listener) {
         listenerRegistry.removeListener(listener);
     }
+
+    // Store delegate to re-post events emitted from the store.
+    private class InternalStoreDelegate implements ClusterStoreDelegate {
+        @Override
+        public void notify(ClusterEvent event) {
+            checkNotNull(event, "Event cannot be null");
+            eventDispatcher.post(event);
+        }
+    }
 }

@@ -30,7 +30,7 @@ import org.onlab.onos.net.device.DeviceService;
 import org.onlab.onos.net.device.PortDescription;
 import org.onlab.onos.net.provider.AbstractProvider;
 import org.onlab.onos.net.provider.ProviderId;
-import org.onlab.onos.store.StoreService;
+import org.onlab.onos.store.common.StoreService;
 import org.onlab.onos.store.device.impl.DistributedDeviceStore;
 import org.onlab.onos.store.impl.StoreManager;
 

@@ -12,7 +12,9 @@ import org.apache.felix.scr.annotations.Activate;
 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.Set;
 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 @@ import static org.onlab.onos.cluster.ControllerNode.State;
  */
 @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 @@ public class DistributedClusterStore extends AbstractDistributedStore
     }
 
     // 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 @@ public class DistributedClusterStore extends AbstractDistributedStore
     }
 
     // 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

@@ -13,6 +13,7 @@ import org.apache.felix.scr.annotations.Service;
 import org.onlab.onos.cluster.ClusterService;
 import org.onlab.onos.cluster.MastershipEvent;
 import org.onlab.onos.cluster.MastershipStore;
+import org.onlab.onos.cluster.MastershipStoreDelegate;
 import org.onlab.onos.cluster.NodeId;
 import org.onlab.onos.net.DeviceId;
 import org.onlab.onos.net.MastershipRole;
@@ -31,7 +32,8 @@ import static com.google.common.cache.CacheBuilder.newBuilder;
  */
 @Component(immediate = true)
 @Service
-public class DistributedMastershipStore extends AbstractDistributedStore
+public class DistributedMastershipStore
+        extends AbstractDistributedStore<MastershipEvent, MastershipStoreDelegate>
         implements MastershipStore {
 
     private IMap<byte[], byte[]> rawMasters;

-package org.onlab.onos.store;
+package org.onlab.onos.store.common;
 
 import com.hazelcast.core.HazelcastInstance;
 

@@ -2,4 +2,4 @@
  * Common abstractions and facilities for implementing distributed store
  * using Hazelcast.
  */
-package org.onlab.onos.store;
+package org.onlab.onos.store.common;

@@ -21,6 +21,7 @@ import org.onlab.onos.net.PortNumber;
 import org.onlab.onos.net.device.DeviceDescription;
 import org.onlab.onos.net.device.DeviceEvent;
 import org.onlab.onos.net.device.DeviceStore;
+import org.onlab.onos.net.device.DeviceStoreDelegate;
 import org.onlab.onos.net.device.PortDescription;
 import org.onlab.onos.net.provider.ProviderId;
 import org.onlab.onos.store.impl.AbsentInvalidatingLoadingCache;
@@ -48,7 +49,8 @@ import static org.slf4j.LoggerFactory.getLogger;
  */
 @Component(immediate = true)
 @Service
-public class DistributedDeviceStore extends AbstractDistributedStore
+public class DistributedDeviceStore
+        extends AbstractDistributedStore<DeviceEvent, DeviceStoreDelegate>
         implements DeviceStore {
 
     private final Logger log = getLogger(getClass());

@@ -10,7 +10,10 @@ import org.apache.felix.scr.annotations.Activate;
 import org.apache.felix.scr.annotations.Component;
 import org.apache.felix.scr.annotations.Reference;
 import org.apache.felix.scr.annotations.ReferenceCardinality;
-import org.onlab.onos.store.StoreService;
+import org.onlab.onos.event.Event;
+import org.onlab.onos.store.AbstractStore;
+import org.onlab.onos.store.StoreDelegate;
+import org.onlab.onos.store.common.StoreService;
 import org.slf4j.Logger;
 
 import static com.google.common.base.Preconditions.checkNotNull;
@@ -20,7 +23,8 @@ import static org.slf4j.LoggerFactory.getLogger;
  * Abstraction of a distributed store based on Hazelcast.
  */
 @Component(componentAbstract = true)
-public abstract class AbstractDistributedStore {
+public abstract class AbstractDistributedStore<E extends Event, D extends StoreDelegate<E>>
+            extends AbstractStore<E, D> {
 
     protected final Logger log = getLogger(getClass());
 

@@ -2,7 +2,7 @@ package org.onlab.onos.store.impl;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
-import org.onlab.onos.store.StoreService;
+import org.onlab.onos.store.common.StoreService;
 
 import com.google.common.base.Optional;
 import com.google.common.cache.CacheLoader;

@@ -21,7 +21,7 @@ import org.onlab.onos.net.MastershipRole;
 import org.onlab.onos.net.Port;
 import org.onlab.onos.net.PortNumber;
 import org.onlab.onos.net.provider.ProviderId;
-import org.onlab.onos.store.StoreService;
+import org.onlab.onos.store.common.StoreService;
 import org.onlab.onos.store.serializers.DefaultPortSerializer;
 import org.onlab.onos.store.serializers.DeviceIdSerializer;
 import org.onlab.onos.store.serializers.IpPrefixSerializer;

@@ -5,10 +5,13 @@ import org.apache.felix.scr.annotations.Activate;
 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;
+import org.onlab.onos.store.AbstractStore;
 import org.onlab.packet.IpPrefix;
 import org.slf4j.Logger;
 
@@ -22,7 +25,9 @@ import static org.slf4j.LoggerFactory.getLogger;
  */
 @Component(immediate = true)
 @Service
-public class SimpleClusterStore implements ClusterStore {
+public class SimpleClusterStore
+        extends AbstractStore<ClusterEvent, ClusterStoreDelegate>
+        implements ClusterStore {
 
     public static final IpPrefix LOCALHOST = IpPrefix.valueOf("127.0.0.1");
 

@@ -97,11 +97,17 @@
         <feature>onos-thirdparty-web</feature>
         <bundle>mvn:org.onlab.onos/onos-app-tvue/1.0.0-SNAPSHOT</bundle>
     </feature>
-    
+
     <feature name="onos-app-fwd" version="1.0.0"
              description="ONOS sample forwarding application">
         <feature>onos-api</feature>
         <bundle>mvn:org.onlab.onos/onos-app-fwd/1.0.0-SNAPSHOT</bundle>
     </feature>
 
+    <feature name="onos-app-foo" version="1.0.0"
+             description="ONOS sample playground application">
+        <feature>onos-api</feature>
+        <bundle>mvn:org.onlab.onos/onos-app-foo/1.0.0-SNAPSHOT</bundle>
+    </feature>
+
 </features>

@@ -51,7 +51,7 @@ perl -pi.old -e "s|^(featuresRepositories=.*)|\1,mvn:org.onlab.onos/onos-feature
     $ONOS_STAGE/$KARAF_DIST/etc/org.apache.karaf.features.cfg 
 
 # Patch the Apache Karaf distribution file to load ONOS features
-perl -pi.old -e 's|^(featuresBoot=.*)|\1,onos-api,onos-core,onos-cli,onos-rest,onos-gui,onos-openflow,onos-app-fwd|' \
+perl -pi.old -e 's|^(featuresBoot=.*)|\1,onos-api,onos-core,onos-cli,onos-rest,onos-gui,onos-openflow,onos-app-fwd,onos-app-foo|' \
     $ONOS_STAGE/$KARAF_DIST/etc/org.apache.karaf.features.cfg
 
 # Patch the Apache Karaf distribution with ONOS branding bundle