Preparing for change in ClusterService/Store implementation.

+package org.onlab.onos.ccc;
+
+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;
+import org.apache.felix.scr.annotations.Service;
+import org.onlab.nio.AcceptorLoop;
+import org.onlab.nio.IOLoop;
+import org.onlab.nio.MessageStream;
+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;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.nio.channels.ByteChannel;
+import java.nio.channels.ServerSocketChannel;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+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.onos.cluster.ControllerNode.State;
+import static org.onlab.packet.IpPrefix.valueOf;
+import static org.onlab.util.Tools.namedThreads;
+
+/**
+ * Distributed implementation of the cluster nodes store.
+ */
+@Component(immediate = true)
+@Service
+public class DistributedClusterStore
+        extends AbstractStore<ClusterEvent, ClusterStoreDelegate>
+        implements ClusterStore {
+
+    private final Logger log = LoggerFactory.getLogger(getClass());
+
+    private static final long SELECT_TIMEOUT = 50;
+    private static final int WORKERS = 3;
+    private static final int COMM_BUFFER_SIZE = 16 * 1024;
+    private static final int COMM_IDLE_TIME = 500;
+
+    private DefaultControllerNode self;
+    private final Map<NodeId, DefaultControllerNode> nodes = new ConcurrentHashMap<>();
+    private final Map<NodeId, State> states = new ConcurrentHashMap<>();
+
+    private final ExecutorService listenExecutor =
+            Executors.newSingleThreadExecutor(namedThreads("onos-listen"));
+    private final ExecutorService commExecutors =
+            Executors.newFixedThreadPool(WORKERS, namedThreads("onos-cluster"));
+    private final ExecutorService heartbeatExecutor =
+            Executors.newSingleThreadExecutor(namedThreads("onos-heartbeat"));
+
+    private ListenLoop listenLoop;
+    private List<CommLoop> commLoops = new ArrayList<>(WORKERS);
+
+    @Activate
+    public void activate() {
+        establishIdentity();
+        startCommunications();
+        startListening();
+        log.info("Started");
+    }
+
+    private void startCommunications() {
+        for (int i = 0; i < WORKERS; i++) {
+            try {
+                CommLoop loop = new CommLoop();
+                commLoops.add(loop);
+                commExecutors.execute(loop);
+            } catch (IOException e) {
+                log.warn("Unable to start comm IO loop", e);
+            }
+        }
+    }
+
+    // Starts listening for connections from peer cluster members.
+    private void startListening() {
+        try {
+            listenLoop = new ListenLoop(self.ip(), self.tcpPort());
+            listenExecutor.execute(listenLoop);
+        } catch (IOException e) {
+            log.error("Unable to listen for cluster connections", e);
+        }
+    }
+
+    // Establishes the controller's own identity.
+    private void establishIdentity() {
+        // For now rely on env. variable.
+        IpPrefix ip = valueOf(System.getenv("ONOS_NIC"));
+        self = new DefaultControllerNode(new NodeId(ip.toString()), ip);
+    }
+
+    @Deactivate
+    public void deactivate() {
+        listenLoop.shutdown();
+        for (CommLoop loop : commLoops) {
+            loop.shutdown();
+        }
+        log.info("Stopped");
+    }
+
+    @Override
+    public ControllerNode getLocalNode() {
+        return self;
+    }
+
+    @Override
+    public Set<ControllerNode> getNodes() {
+        ImmutableSet.Builder<ControllerNode> builder = ImmutableSet.builder();
+        return builder.addAll(nodes.values()).build();
+    }
+
+    @Override
+    public ControllerNode getNode(NodeId nodeId) {
+        return nodes.get(nodeId);
+    }
+
+    @Override
+    public State getState(NodeId nodeId) {
+        State state = states.get(nodeId);
+        return state == null ? State.INACTIVE : state;
+    }
+
+    @Override
+    public ControllerNode addNode(NodeId nodeId, IpPrefix ip, int tcpPort) {
+        DefaultControllerNode node = new DefaultControllerNode(nodeId, ip, tcpPort);
+        nodes.put(nodeId, node);
+        return node;
+    }
+
+    @Override
+    public void removeNode(NodeId nodeId) {
+        nodes.remove(nodeId);
+    }
+
+    // Listens and accepts inbound connections from other cluster nodes.
+    private class ListenLoop extends AcceptorLoop {
+        ListenLoop(IpPrefix ip, int tcpPort) throws IOException {
+            super(SELECT_TIMEOUT, new InetSocketAddress(getByAddress(ip.toOctets()), tcpPort));
+        }
+
+        @Override
+        protected void acceptConnection(ServerSocketChannel channel) throws IOException {
+
+        }
+    }
+
+    private class CommLoop extends IOLoop<TLVMessage, TLVMessageStream> {
+        CommLoop() throws IOException {
+            super(SELECT_TIMEOUT);
+        }
+
+        @Override
+        protected TLVMessageStream createStream(ByteChannel byteChannel) {
+            return new TLVMessageStream(this, byteChannel, COMM_BUFFER_SIZE, COMM_IDLE_TIME);
+        }
+
+        @Override
+        protected void processMessages(List<TLVMessage> messages, MessageStream<TLVMessage> stream) {
+
+        }
+    }
+}

+package org.onlab.onos.ccc;
+
+import org.onlab.nio.AbstractMessage;
+
+import java.util.Objects;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+
+/**
+ * Base message for cluster-wide communications using TLVs.
+ */
+public class TLVMessage extends AbstractMessage {
+
+    private final int type;
+    private final Object data;
+
+    /**
+     * Creates an immutable TLV message.
+     *
+     * @param type   message type
+     * @param length message length
+     * @param data   message data
+     */
+    public TLVMessage(int type, int length, Object data) {
+        this.length = length;
+        this.type = type;
+        this.data = data;
+    }
+
+    /**
+     * Returns the message type indicator.
+     *
+     * @return message type
+     */
+    public int type() {
+        return type;
+    }
+
+    /**
+     * Returns the data object.
+     *
+     * @return message data
+     */
+    public Object data() {
+        return data;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(type, data);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+        final TLVMessage other = (TLVMessage) obj;
+        return Objects.equals(this.type, other.type) &&
+                Objects.equals(this.data, other.data);
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this).add("type", type).add("length", length).toString();
+    }
+
+}

+package org.onlab.onos.ccc;
+
+import org.onlab.nio.IOLoop;
+import org.onlab.nio.MessageStream;
+
+import java.nio.ByteBuffer;
+import java.nio.channels.ByteChannel;
+
+import static com.google.common.base.Preconditions.checkState;
+
+/**
+ * Stream for transferring TLV messages between cluster members.
+ */
+public class TLVMessageStream extends MessageStream<TLVMessage> {
+
+    private static final long MARKER = 0xfeedcafecafefeedL;
+
+    /**
+     * Creates a message stream associated with the specified IO loop and
+     * backed by the given byte channel.
+     *
+     * @param loop          IO loop
+     * @param byteChannel   backing byte channel
+     * @param bufferSize    size of the backing byte buffers
+     * @param maxIdleMillis maximum number of millis the stream can be idle
+     */
+    protected TLVMessageStream(IOLoop<TLVMessage, ?> loop, ByteChannel byteChannel,
+                               int bufferSize, int maxIdleMillis) {
+        super(loop, byteChannel, bufferSize, maxIdleMillis);
+    }
+
+    @Override
+    protected TLVMessage read(ByteBuffer buffer) {
+        long marker = buffer.getLong();
+        checkState(marker == MARKER, "Incorrect message marker");
+
+        int type = buffer.getInt();
+        int length = buffer.getInt();
+
+        // TODO: add deserialization hook here
+
+        return new TLVMessage(type, length, null);
+    }
+
+    @Override
+    protected void write(TLVMessage message, ByteBuffer buffer) {
+        buffer.putLong(MARKER);
+        buffer.putInt(message.type());
+        buffer.putInt(message.length());
+
+        // TODO: add serialization hook here
+    }
+}