Added Netty based messaging. Updated cluster management to use Netty based messaging
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterCommunicationAdminService.java b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterCommunicationAdminService.java
deleted file mode 100644
index 22ed9de..0000000
--- a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterCommunicationAdminService.java
+++ /dev/null
@@ -1,36 +0,0 @@
-package org.onlab.onos.store.cluster.impl;
-
-import org.onlab.onos.cluster.DefaultControllerNode;
-
-/**
- * Service for administering communications manager.
- */
-public interface ClusterCommunicationAdminService {
-
-    /**
-     * Adds the node to the list of monitored nodes.
-     *
-     * @param node node to be added
-     */
-    void addNode(DefaultControllerNode node);
-
-    /**
-     * Removes the node from the list of monitored nodes.
-     *
-     * @param node node to be removed
-     */
-    void removeNode(DefaultControllerNode node);
-
-    /**
-     * Starts-up the communications engine.
-     *
-     * @param localNode local controller node
-     * @param delegate nodes delegate
-     */
-    void startUp(DefaultControllerNode localNode, ClusterNodesDelegate delegate);
-
-    /**
-     * Clears all nodes and streams as part of leaving the cluster.
-     */
-    void clearAllNodesAndStreams();
-}
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterCommunicationManager.java b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterCommunicationManager.java
deleted file mode 100644
index 2e2887c..0000000
--- a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterCommunicationManager.java
+++ /dev/null
@@ -1,354 +0,0 @@
-package org.onlab.onos.store.cluster.impl;
-
-import com.google.common.collect.HashMultimap;
-import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.Multimap;
-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.apache.felix.scr.annotations.Service;
-import org.onlab.onos.cluster.DefaultControllerNode;
-import org.onlab.onos.cluster.NodeId;
-import org.onlab.onos.store.cluster.messaging.ClusterCommunicationService;
-import org.onlab.onos.store.cluster.messaging.ClusterMembershipMessage;
-import org.onlab.onos.store.cluster.messaging.ClusterMessage;
-import org.onlab.onos.store.cluster.messaging.HelloMessage;
-import org.onlab.onos.store.cluster.messaging.LeavingMemberMessage;
-import org.onlab.onos.store.cluster.messaging.MessageSubject;
-import org.onlab.onos.store.cluster.messaging.MessageSubscriber;
-import org.onlab.onos.store.cluster.messaging.NewMemberMessage;
-import org.onlab.onos.store.cluster.messaging.SerializationService;
-import org.onlab.packet.IpPrefix;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import java.io.IOException;
-import java.net.InetSocketAddress;
-import java.net.SocketAddress;
-import java.nio.channels.SocketChannel;
-import java.util.ArrayList;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
-import java.util.Timer;
-import java.util.TimerTask;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-
-import static java.net.InetAddress.getByAddress;
-import static org.onlab.util.Tools.namedThreads;
-
-/**
- * Implements the cluster communication services to use by other stores.
- */
-@Component(immediate = true)
-@Service
-public class ClusterCommunicationManager
-        implements ClusterCommunicationService, ClusterCommunicationAdminService {
-
-    private final Logger log = LoggerFactory.getLogger(getClass());
-
-    private static final long CONNECTION_CUSTODIAN_DELAY = 100L;
-    private static final long CONNECTION_CUSTODIAN_FREQUENCY = 2000;
-
-    private static final long START_TIMEOUT = 1000;
-    private static final int WORKERS = 3;
-
-    private ClusterConnectionListener connectionListener;
-    private List<ClusterIOWorker> workers = new ArrayList<>(WORKERS);
-
-    private DefaultControllerNode localNode;
-    private ClusterNodesDelegate nodesDelegate;
-
-    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
-    protected SerializationService serializationService;
-
-    // Nodes to be monitored to make sure they have a connection.
-    private final Set<DefaultControllerNode> nodes = new HashSet<>();
-
-    // Means to track message streams to other nodes.
-    private final Map<NodeId, ClusterMessageStream> streams = new ConcurrentHashMap<>();
-
-    // TODO: use something different that won't require synchronization
-    private Multimap<MessageSubject, MessageSubscriber> subscribers = HashMultimap.create();
-
-    // Executor pools for listening and managing connections to other nodes.
-    private final ExecutorService listenExecutor =
-            Executors.newSingleThreadExecutor(namedThreads("onos-comm-listen"));
-    private final ExecutorService commExecutors =
-            Executors.newFixedThreadPool(WORKERS, namedThreads("onos-comm-cluster"));
-    private final ExecutorService heartbeatExecutor =
-            Executors.newSingleThreadExecutor(namedThreads("onos-comm-heartbeat"));
-
-    private final Timer timer = new Timer("onos-comm-initiator");
-    private final TimerTask connectionCustodian = new ConnectionCustodian();
-    private MembershipSubscriber membershipSubscriber = new MembershipSubscriber();
-
-    @Activate
-    public void activate() {
-        addSubscriber(MessageSubject.NEW_MEMBER, membershipSubscriber);
-        addSubscriber(MessageSubject.LEAVING_MEMBER, membershipSubscriber);
-        log.info("Activated but waiting for delegate");
-    }
-
-    @Deactivate
-    public void deactivate() {
-        removeSubscriber(MessageSubject.NEW_MEMBER, membershipSubscriber);
-        removeSubscriber(MessageSubject.LEAVING_MEMBER, membershipSubscriber);
-
-        connectionCustodian.cancel();
-        if (connectionListener != null) {
-            connectionListener.shutdown();
-            for (ClusterIOWorker worker : workers) {
-                worker.shutdown();
-            }
-        }
-        log.info("Stopped");
-    }
-
-    @Override
-    public boolean send(ClusterMessage message) {
-        boolean ok = true;
-        for (DefaultControllerNode node : nodes) {
-            if (!node.equals(localNode)) {
-                ok = send(message, node.id()) && ok;
-            }
-        }
-        return ok;
-    }
-
-    @Override
-    public boolean send(ClusterMessage message, NodeId toNodeId) {
-        ClusterMessageStream stream = streams.get(toNodeId);
-        if (stream != null && !toNodeId.equals(localNode.id())) {
-            try {
-                stream.write(message);
-                return true;
-            } catch (IOException e) {
-                log.warn("Unable to send message {} to node {}",
-                         message.subject(), toNodeId);
-            }
-        }
-        return false;
-    }
-
-    @Override
-    public synchronized void addSubscriber(MessageSubject subject,
-                                           MessageSubscriber subscriber) {
-        subscribers.put(subject, subscriber);
-    }
-
-    @Override
-    public synchronized void removeSubscriber(MessageSubject subject,
-                                              MessageSubscriber subscriber) {
-        subscribers.remove(subject, subscriber);
-    }
-
-    @Override
-    public Set<MessageSubscriber> getSubscribers(MessageSubject subject) {
-        return ImmutableSet.copyOf(subscribers.get(subject));
-    }
-
-    @Override
-    public void addNode(DefaultControllerNode node) {
-        nodes.add(node);
-    }
-
-    @Override
-    public void removeNode(DefaultControllerNode node) {
-        send(new LeavingMemberMessage(node.id()));
-        nodes.remove(node);
-        ClusterMessageStream stream = streams.remove(node.id());
-        if (stream != null) {
-            stream.close();
-        }
-    }
-
-    @Override
-    public void startUp(DefaultControllerNode localNode,
-                        ClusterNodesDelegate delegate) {
-        this.localNode = localNode;
-        this.nodesDelegate = delegate;
-
-        startCommunications();
-        startListening();
-        startInitiatingConnections();
-        log.info("Started");
-    }
-
-    @Override
-    public void clearAllNodesAndStreams() {
-        nodes.clear();
-        send(new LeavingMemberMessage(localNode.id()));
-        for (ClusterMessageStream stream : streams.values()) {
-            stream.close();
-        }
-        streams.clear();
-    }
-
-    /**
-     * Dispatches the specified message to all subscribers to its subject.
-     *
-     * @param message    message to dispatch
-     * @param fromNodeId node from which the message was received
-     */
-    void dispatch(ClusterMessage message, NodeId fromNodeId) {
-        Set<MessageSubscriber> set = getSubscribers(message.subject());
-        if (set != null) {
-            for (MessageSubscriber subscriber : set) {
-                subscriber.receive(message, fromNodeId);
-            }
-        }
-    }
-
-    /**
-     * Adds the stream associated with the specified node.
-     *
-     * @param nodeId  newly detected cluster node id
-     * @param ip      node IP listen address
-     * @param tcpPort node TCP listen port
-     * @return controller node bound to the stream
-     */
-    DefaultControllerNode addNodeStream(NodeId nodeId, IpPrefix ip, int tcpPort,
-                                        ClusterMessageStream stream) {
-        DefaultControllerNode node = nodesDelegate.nodeDetected(nodeId, ip, tcpPort);
-        stream.setNode(node);
-        streams.put(node.id(), stream);
-        send(new NewMemberMessage(node.id(), node.ip(), node.tcpPort()));
-        return node;
-    }
-
-    /**
-     * Removes the stream associated with the specified node.
-     *
-     * @param node node whose stream to remove
-     */
-    void removeNodeStream(DefaultControllerNode node) {
-        nodesDelegate.nodeVanished(node.id());
-        streams.remove(node.id());
-    }
-
-    /**
-     * Finds the least utilized IO worker.
-     *
-     * @return IO worker
-     */
-    ClusterIOWorker findWorker() {
-        ClusterIOWorker leastUtilized = null;
-        int minCount = Integer.MAX_VALUE;
-        for (ClusterIOWorker worker : workers) {
-            int count = worker.streamCount();
-            if (count == 0) {
-                return worker;
-            }
-
-            if (count < minCount) {
-                leastUtilized = worker;
-                minCount = count;
-            }
-        }
-        return leastUtilized;
-    }
-
-    /**
-     * Kicks off the IO loops and waits for them to startup.
-     */
-    private void startCommunications() {
-        HelloMessage hello = new HelloMessage(localNode.id(), localNode.ip(),
-                                              localNode.tcpPort());
-        for (int i = 0; i < WORKERS; i++) {
-            try {
-                ClusterIOWorker worker =
-                        new ClusterIOWorker(this, serializationService, hello);
-                workers.add(worker);
-                commExecutors.execute(worker);
-            } catch (IOException e) {
-                log.warn("Unable to start communication worker", e);
-            }
-        }
-
-        // Wait for the IO loops to start
-        for (ClusterIOWorker loop : workers) {
-            if (!loop.awaitStart(START_TIMEOUT)) {
-                log.warn("Comm loop did not start on-time; moving on...");
-            }
-        }
-    }
-
-    /**
-     * Starts listening for connections from peer cluster members.
-     */
-    private void startListening() {
-        try {
-            connectionListener =
-                    new ClusterConnectionListener(this, localNode.ip(), localNode.tcpPort());
-            listenExecutor.execute(connectionListener);
-            if (!connectionListener.awaitStart(START_TIMEOUT)) {
-                log.warn("Listener did not start on-time; moving on...");
-            }
-        } catch (IOException e) {
-            log.error("Unable to listen for cluster connections", e);
-        }
-    }
-
-    /**
-     * Attempts to connect to any nodes that do not have an associated connection.
-     */
-    private void startInitiatingConnections() {
-        timer.schedule(connectionCustodian, CONNECTION_CUSTODIAN_DELAY,
-                       CONNECTION_CUSTODIAN_FREQUENCY);
-    }
-
-    /**
-     * Initiates open connection request and registers the pending socket
-     * channel with the given IO worker.
-     *
-     * @param worker loop with which the channel should be registered
-     * @throws java.io.IOException if the socket could not be open or connected
-     */
-    private void initiateConnection(DefaultControllerNode node,
-                                    ClusterIOWorker worker) throws IOException {
-        SocketAddress sa = new InetSocketAddress(getByAddress(node.ip().toOctets()), node.tcpPort());
-        SocketChannel ch = SocketChannel.open();
-        ch.configureBlocking(false);
-        ch.connect(sa);
-        worker.connectStream(ch);
-    }
-
-    // Sweeps through all controller nodes and attempts to open connection to
-    // those that presently do not have one.
-    private class ConnectionCustodian extends TimerTask {
-        @Override
-        public void run() {
-            for (DefaultControllerNode node : nodes) {
-                if (!node.id().equals(localNode.id()) && !streams.containsKey(node.id())) {
-                    try {
-                        initiateConnection(node, findWorker());
-                    } catch (IOException e) {
-                        log.debug("Unable to connect", e);
-                    }
-                }
-            }
-        }
-    }
-
-    private class MembershipSubscriber implements MessageSubscriber {
-        @Override
-        public void receive(ClusterMessage message, NodeId fromNodeId) {
-            MessageSubject subject = message.subject();
-            ClusterMembershipMessage cmm = (ClusterMembershipMessage) message;
-            if (message.subject() == MessageSubject.NEW_MEMBER) {
-                log.info("Node {} arrived", cmm.nodeId());
-                nodesDelegate.nodeDetected(cmm.nodeId(), cmm.ipAddress(), cmm.tcpPort());
-
-            } else if (subject == MessageSubject.LEAVING_MEMBER) {
-                log.info("Node {} is leaving", cmm.nodeId());
-                nodesDelegate.nodeRemoved(cmm.nodeId());
-            }
-        }
-    }
-}
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterConnectionListener.java b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterConnectionListener.java
deleted file mode 100644
index 36d5ab4..0000000
--- a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterConnectionListener.java
+++ /dev/null
@@ -1,47 +0,0 @@
-package org.onlab.onos.store.cluster.impl;
-
-import org.onlab.nio.AcceptorLoop;
-import org.onlab.packet.IpPrefix;
-
-import java.io.IOException;
-import java.net.InetSocketAddress;
-import java.net.Socket;
-import java.nio.channels.ServerSocketChannel;
-import java.nio.channels.SocketChannel;
-
-import static java.net.InetAddress.getByAddress;
-
-/**
- * Listens to inbound connection requests and accepts them.
- */
-public class ClusterConnectionListener extends AcceptorLoop {
-
-    private static final long SELECT_TIMEOUT = 50;
-    private static final int COMM_BUFFER_SIZE = 32 * 1024;
-
-    private static final boolean SO_NO_DELAY = false;
-    private static final int SO_SEND_BUFFER_SIZE = COMM_BUFFER_SIZE;
-    private static final int SO_RCV_BUFFER_SIZE = COMM_BUFFER_SIZE;
-
-    private final ClusterCommunicationManager manager;
-
-    ClusterConnectionListener(ClusterCommunicationManager manager,
-                              IpPrefix ip, int tcpPort) throws IOException {
-        super(SELECT_TIMEOUT, new InetSocketAddress(getByAddress(ip.toOctets()), tcpPort));
-        this.manager = manager;
-    }
-
-    @Override
-    protected void acceptConnection(ServerSocketChannel channel) throws IOException {
-        SocketChannel sc = channel.accept();
-        sc.configureBlocking(false);
-
-        Socket so = sc.socket();
-        so.setTcpNoDelay(SO_NO_DELAY);
-        so.setReceiveBufferSize(SO_RCV_BUFFER_SIZE);
-        so.setSendBufferSize(SO_SEND_BUFFER_SIZE);
-
-        manager.findWorker().acceptStream(sc);
-    }
-
-}
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterIOWorker.java b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterIOWorker.java
deleted file mode 100644
index d442cc8..0000000
--- a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterIOWorker.java
+++ /dev/null
@@ -1,120 +0,0 @@
-package org.onlab.onos.store.cluster.impl;
-
-import org.onlab.nio.IOLoop;
-import org.onlab.nio.MessageStream;
-import org.onlab.onos.cluster.DefaultControllerNode;
-import org.onlab.onos.cluster.NodeId;
-import org.onlab.onos.store.cluster.messaging.ClusterMessage;
-import org.onlab.onos.store.cluster.messaging.HelloMessage;
-import org.onlab.onos.store.cluster.messaging.SerializationService;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import java.io.IOException;
-import java.net.InetSocketAddress;
-import java.nio.channels.ByteChannel;
-import java.nio.channels.SelectionKey;
-import java.nio.channels.SocketChannel;
-import java.util.List;
-import java.util.Objects;
-
-import static org.onlab.packet.IpPrefix.valueOf;
-
-/**
- * Performs the IO operations related to a cluster-wide communications.
- */
-public class ClusterIOWorker extends
-        IOLoop<ClusterMessage, ClusterMessageStream> {
-
-    private final Logger log = LoggerFactory.getLogger(getClass());
-
-    private static final long SELECT_TIMEOUT = 50;
-
-    private final ClusterCommunicationManager manager;
-    private final SerializationService serializationService;
-    private final ClusterMessage helloMessage;
-
-    /**
-     * Creates a new cluster IO worker.
-     *
-     * @param manager              parent comms manager
-     * @param serializationService serialization service for encode/decode
-     * @param helloMessage         hello message for greeting peers
-     * @throws IOException if errors occur during IO loop ignition
-     */
-    ClusterIOWorker(ClusterCommunicationManager manager,
-                    SerializationService serializationService,
-                    ClusterMessage helloMessage) throws IOException {
-        super(SELECT_TIMEOUT);
-        this.manager = manager;
-        this.serializationService = serializationService;
-        this.helloMessage = helloMessage;
-    }
-
-    @Override
-    protected ClusterMessageStream createStream(ByteChannel byteChannel) {
-        return new ClusterMessageStream(serializationService, this, byteChannel);
-    }
-
-    @Override
-    protected void processMessages(List<ClusterMessage> messages, MessageStream<ClusterMessage> stream) {
-        NodeId nodeId = getNodeId(messages, (ClusterMessageStream) stream);
-        for (ClusterMessage message : messages) {
-            manager.dispatch(message, nodeId);
-        }
-    }
-
-    // Retrieves the node from the stream. If one is not bound, it attempts
-    // to bind it using the knowledge that the first message must be a hello.
-    private NodeId getNodeId(List<ClusterMessage> messages, ClusterMessageStream stream) {
-        DefaultControllerNode node = stream.node();
-        if (node == null && !messages.isEmpty()) {
-            ClusterMessage firstMessage = messages.get(0);
-            if (firstMessage instanceof HelloMessage) {
-                HelloMessage hello = (HelloMessage) firstMessage;
-                node = manager.addNodeStream(hello.nodeId(), hello.ipAddress(),
-                                             hello.tcpPort(), stream);
-            }
-        }
-        return node != null ? node.id() : null;
-    }
-
-    @Override
-    public ClusterMessageStream acceptStream(SocketChannel channel) {
-        ClusterMessageStream stream = super.acceptStream(channel);
-        try {
-            InetSocketAddress sa = (InetSocketAddress) channel.getRemoteAddress();
-            log.info("Accepted connection from node {}", valueOf(sa.getAddress().getAddress()));
-            stream.write(helloMessage);
-
-        } catch (IOException e) {
-            log.warn("Unable to accept connection from an unknown end-point", e);
-        }
-        return stream;
-    }
-
-    @Override
-    protected void connect(SelectionKey key) throws IOException {
-        try {
-            super.connect(key);
-            ClusterMessageStream stream = (ClusterMessageStream) key.attachment();
-            stream.write(helloMessage);
-
-        } catch (IOException e) {
-            if (!Objects.equals(e.getMessage(), "Connection refused")) {
-                throw e;
-            }
-        }
-    }
-
-    @Override
-    protected void removeStream(MessageStream<ClusterMessage> stream) {
-        DefaultControllerNode node = ((ClusterMessageStream) stream).node();
-        if (node != null) {
-            log.info("Closed connection to node {}", node.id());
-            manager.removeNodeStream(node);
-        }
-        super.removeStream(stream);
-    }
-
-}
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterMessageStream.java b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterMessageStream.java
deleted file mode 100644
index d182aa1..0000000
--- a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/ClusterMessageStream.java
+++ /dev/null
@@ -1,69 +0,0 @@
-package org.onlab.onos.store.cluster.impl;
-
-import org.onlab.nio.IOLoop;
-import org.onlab.nio.MessageStream;
-import org.onlab.onos.cluster.DefaultControllerNode;
-import org.onlab.onos.store.cluster.messaging.ClusterMessage;
-import org.onlab.onos.store.cluster.messaging.SerializationService;
-
-import java.nio.ByteBuffer;
-import java.nio.channels.ByteChannel;
-
-import static com.google.common.base.Preconditions.checkState;
-
-/**
- * Stream for transferring messages between two cluster members.
- */
-public class ClusterMessageStream extends MessageStream<ClusterMessage> {
-
-    private static final int COMM_BUFFER_SIZE = 32 * 1024;
-    private static final int COMM_IDLE_TIME = 500;
-
-    private DefaultControllerNode node;
-    private SerializationService serializationService;
-
-    /**
-     * Creates a message stream associated with the specified IO loop and
-     * backed by the given byte channel.
-     *
-     * @param serializationService service for encoding/decoding messages
-     * @param loop                 IO loop
-     * @param byteChannel          backing byte channel
-     */
-    public ClusterMessageStream(SerializationService serializationService,
-                                IOLoop<ClusterMessage, ?> loop,
-                                ByteChannel byteChannel) {
-        super(loop, byteChannel, COMM_BUFFER_SIZE, COMM_IDLE_TIME);
-        this.serializationService = serializationService;
-    }
-
-    /**
-     * Returns the node with which this stream is associated.
-     *
-     * @return controller node
-     */
-    public DefaultControllerNode node() {
-        return node;
-    }
-
-    /**
-     * Sets the node with which this stream is affiliated.
-     *
-     * @param node controller node
-     */
-    public void setNode(DefaultControllerNode node) {
-        checkState(this.node == null, "Stream is already bound to a node");
-        this.node = node;
-    }
-
-    @Override
-    protected ClusterMessage read(ByteBuffer buffer) {
-        return serializationService.decode(buffer);
-    }
-
-    @Override
-    protected void write(ClusterMessage message, ByteBuffer buffer) {
-        serializationService.encode(message, buffer);
-    }
-
-}
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/DistributedClusterStore.java b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/DistributedClusterStore.java
index d4b7289..e25c964 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/DistributedClusterStore.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/DistributedClusterStore.java
@@ -1,6 +1,11 @@
 package org.onlab.onos.store.cluster.impl;
 
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.RemovalListener;
+import com.google.common.cache.RemovalNotification;
 import com.google.common.collect.ImmutableSet;
+
 import org.apache.felix.scr.annotations.Activate;
 import org.apache.felix.scr.annotations.Component;
 import org.apache.felix.scr.annotations.Deactivate;
@@ -14,6 +19,8 @@
 import org.onlab.onos.cluster.DefaultControllerNode;
 import org.onlab.onos.cluster.NodeId;
 import org.onlab.onos.store.AbstractStore;
+import org.onlab.onos.store.cluster.messaging.ClusterCommunicationAdminService;
+import org.onlab.onos.store.cluster.messaging.impl.OnosClusterCommunicationManager;
 import org.onlab.packet.IpPrefix;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -22,6 +29,7 @@
 import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.TimeUnit;
 
 import static org.onlab.onos.cluster.ControllerNode.State;
 import static org.onlab.packet.IpPrefix.valueOf;
@@ -40,21 +48,25 @@
     private DefaultControllerNode localNode;
     private final Map<NodeId, DefaultControllerNode> nodes = new ConcurrentHashMap<>();
     private final Map<NodeId, State> states = new ConcurrentHashMap<>();
+    private final Cache<NodeId, ControllerNode> livenessCache = CacheBuilder.newBuilder()
+            .maximumSize(1000)
+            .expireAfterWrite(OnosClusterCommunicationManager.HEART_BEAT_INTERVAL_MILLIS * 3, TimeUnit.MILLISECONDS)
+            .removalListener(new LivenessCacheRemovalListener()).build();
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
-    private ClusterCommunicationAdminService communicationAdminService;
+    private ClusterCommunicationAdminService clusterCommunicationAdminService;
 
     private final ClusterNodesDelegate nodesDelegate = new InnerNodesDelegate();
 
     @Activate
-    public void activate() {
+    public void activate() throws IOException {
         loadClusterDefinition();
         establishSelfIdentity();
 
         // Start-up the comm service and prime it with the loaded nodes.
-        communicationAdminService.startUp(localNode, nodesDelegate);
+        clusterCommunicationAdminService.initialize(localNode, nodesDelegate);
         for (DefaultControllerNode node : nodes.values()) {
-            communicationAdminService.addNode(node);
+            clusterCommunicationAdminService.addNode(node);
         }
         log.info("Started");
     }
@@ -121,15 +133,13 @@
     public ControllerNode addNode(NodeId nodeId, IpPrefix ip, int tcpPort) {
         DefaultControllerNode node = new DefaultControllerNode(nodeId, ip, tcpPort);
         nodes.put(nodeId, node);
-        communicationAdminService.addNode(node);
+        clusterCommunicationAdminService.addNode(node);
         return node;
     }
 
     @Override
     public void removeNode(NodeId nodeId) {
         if (nodeId.equals(localNode.id())) {
-            // We are being ejected from the cluster, so remove all other nodes.
-            communicationAdminService.clearAllNodesAndStreams();
             nodes.clear();
             nodes.put(localNode.id(), localNode);
 
@@ -137,7 +147,7 @@
             // Remove the other node.
             DefaultControllerNode node = nodes.remove(nodeId);
             if (node != null) {
-                communicationAdminService.removeNode(node);
+                clusterCommunicationAdminService.removeNode(node);
             }
         }
     }
@@ -151,6 +161,7 @@
                 node = (DefaultControllerNode) addNode(nodeId, ip, tcpPort);
             }
             states.put(nodeId, State.ACTIVE);
+            livenessCache.put(nodeId, node);
             return node;
         }
 
@@ -165,4 +176,13 @@
         }
     }
 
+    private class LivenessCacheRemovalListener implements RemovalListener<NodeId, ControllerNode> {
+
+        @Override
+        public void onRemoval(RemovalNotification<NodeId, ControllerNode> entry) {
+            NodeId nodeId = entry.getKey();
+            log.warn("Failed to receive heartbeats from controller: " + nodeId);
+            nodesDelegate.nodeVanished(nodeId);
+        }
+    }
 }
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/MessageSerializer.java b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/MessageSerializer.java
index c6ebca9..98e80f7 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/MessageSerializer.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/impl/MessageSerializer.java
@@ -21,12 +21,7 @@
 import org.onlab.onos.net.Port;
 import org.onlab.onos.net.PortNumber;
 import org.onlab.onos.net.provider.ProviderId;
-import org.onlab.onos.store.cluster.messaging.ClusterMessage;
-import org.onlab.onos.store.cluster.messaging.EchoMessage;
-import org.onlab.onos.store.cluster.messaging.LeavingMemberMessage;
-import org.onlab.onos.store.cluster.messaging.HelloMessage;
 import org.onlab.onos.store.cluster.messaging.MessageSubject;
-import org.onlab.onos.store.cluster.messaging.NewMemberMessage;
 import org.onlab.onos.store.cluster.messaging.SerializationService;
 import org.onlab.onos.store.serializers.ConnectPointSerializer;
 import org.onlab.onos.store.serializers.DefaultLinkSerializer;
@@ -43,12 +38,9 @@
 import org.slf4j.LoggerFactory;
 
 import java.net.URI;
-import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.HashMap;
 
-import static com.google.common.base.Preconditions.checkState;
-
 /**
  * Factory for parsing messages sent between cluster members.
  */
@@ -96,11 +88,7 @@
 
                           Link.Type.class,
 
-                          MessageSubject.class,
-                          HelloMessage.class,
-                          NewMemberMessage.class,
-                          LeavingMemberMessage.class,
-                          EchoMessage.class
+                          MessageSubject.class
                 )
                 .register(IpPrefix.class, new IpPrefixSerializer())
                 .register(URI.class, new URISerializer())
@@ -118,49 +106,12 @@
 
 
     @Override
-    public ClusterMessage decode(ByteBuffer buffer) {
-        try {
-            // Do we have enough bytes to read the header? If not, bail.
-            if (buffer.remaining() < METADATA_LENGTH) {
-                return null;
-            }
-
-            // Peek at the length and if we have enough to read the entire message
-            // go ahead, otherwise bail.
-            int length = buffer.getInt(buffer.position() + LENGTH_OFFSET);
-            if (buffer.remaining() < length) {
-                return null;
-            }
-
-            // At this point, we have enough data to read a complete message.
-            long marker = buffer.getLong();
-            checkState(marker == MARKER, "Incorrect message marker");
-            length = buffer.getInt();
-
-            // TODO: sanity checking for length
-            byte[] data = new byte[length - METADATA_LENGTH];
-            buffer.get(data);
-            return (ClusterMessage) serializerPool.deserialize(data);
-
-        } catch (Exception e) {
-            // TODO: recover from exceptions by forwarding stream to next marker
-            log.warn("Unable to decode message due to: " + e);
-        }
-        return null;
+    public Object decode(byte[] data) {
+        return serializerPool.deserialize(data);
     }
 
     @Override
-    public void encode(ClusterMessage message, ByteBuffer buffer) {
-        try {
-            byte[] data = serializerPool.serialize(message);
-            buffer.putLong(MARKER);
-            buffer.putInt(data.length + METADATA_LENGTH);
-            buffer.put(data);
-
-        } catch (Exception e) {
-            // TODO: recover from exceptions by forwarding stream to next marker
-            log.warn("Unable to encode message due to: " + e);
-        }
+    public byte[] encode(Object payload) {
+        return serializerPool.serialize(payload);
     }
-
-}
+}
\ No newline at end of file