Netty native transport (epoll) support

@@ -22,10 +22,8 @@ import org.onlab.onos.store.cluster.messaging.ClusterMessage;
 import org.onlab.onos.store.cluster.messaging.ClusterMessageHandler;
 import org.onlab.onos.store.cluster.messaging.ClusterMessageResponse;
 import org.onlab.onos.store.cluster.messaging.MessageSubject;
-import org.onlab.onos.store.serializers.ClusterMessageSerializer;
 import org.onlab.onos.store.serializers.KryoNamespaces;
 import org.onlab.onos.store.serializers.KryoSerializer;
-import org.onlab.onos.store.serializers.MessageSubjectSerializer;
 import org.onlab.util.KryoNamespace;
 import org.onlab.netty.Endpoint;
 import org.onlab.netty.Message;

@@ -17,6 +17,8 @@ import io.netty.channel.ChannelInitializer;
 import io.netty.channel.ChannelOption;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.channel.epoll.EpollEventLoopGroup;
+import io.netty.channel.epoll.EpollSocketChannel;
 import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.channel.socket.SocketChannel;
 import io.netty.channel.socket.nio.NioServerSocketChannel;
@@ -41,7 +43,8 @@ public class NettyMessagingService implements MessagingService {
     private final int port;
     private final Endpoint localEp;
     private final EventLoopGroup bossGroup = new NioEventLoopGroup();
-    private final EventLoopGroup workerGroup = new NioEventLoopGroup();
+    private EventLoopGroup workerGroup;
+    private Class<? extends Channel> channelClass;
     private final ConcurrentMap<String, MessageHandler> handlers = new ConcurrentHashMap<>();
     private final Cache<Long, AsyncResponse> responseFutures = CacheBuilder.newBuilder()
             .maximumSize(100000)
@@ -52,6 +55,17 @@ public class NettyMessagingService implements MessagingService {
     private final GenericKeyedObjectPool<Endpoint, Channel> channels
             = new GenericKeyedObjectPool<Endpoint, Channel>(new OnosCommunicationChannelFactory());
 
+    // TODO: make this configurable.
+    private void initEventLoopGroup() {
+        try {
+            workerGroup = new EpollEventLoopGroup();
+            channelClass = EpollSocketChannel.class;
+        } catch (Throwable t) {
+            workerGroup = new NioEventLoopGroup();
+            channelClass = NioSocketChannel.class;
+        }
+    }
+
     public NettyMessagingService() {
         // TODO: Default port should be configurable.
         this(8080);
@@ -71,6 +85,7 @@ public class NettyMessagingService implements MessagingService {
     public void activate() throws Exception {
         channels.setTestOnBorrow(true);
         channels.setTestOnReturn(true);
+        initEventLoopGroup();
         startAcceptingConnections();
     }
 
@@ -173,7 +188,7 @@ public class NettyMessagingService implements MessagingService {
             bootstrap.group(workerGroup);
             // TODO: Make this faster:
             // http://normanmaurer.me/presentations/2014-facebook-eng-netty/slides.html#37.0
-            bootstrap.channel(NioSocketChannel.class);
+            bootstrap.channel(channelClass);
             bootstrap.option(ChannelOption.SO_KEEPALIVE, true);
             bootstrap.handler(new OnosCommunicationChannelInitializer());
             // Start the client.