Netty performance improvements

 package org.onlab.netty;
 
 import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelHandler.Sharable;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.MessageToByteEncoder;
 
 /**
  * Encode InternalMessage out into a byte buffer.
  */
+@Sharable
 public class MessageEncoder extends MessageToByteEncoder<InternalMessage> {
 
     // onosiscool in ascii

@@ -11,6 +11,7 @@ import io.netty.bootstrap.ServerBootstrap;
 import io.netty.buffer.PooledByteBufAllocator;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInitializer;
 import io.netty.channel.ChannelOption;
@@ -37,14 +38,19 @@ public class NettyMessagingService implements MessagingService {
 
     private final Logger log = LoggerFactory.getLogger(getClass());
 
-    private GenericKeyedObjectPool<Endpoint, Channel> channels;
-
     private final int port;
+    private final Endpoint localEp;
     private final EventLoopGroup bossGroup = new NioEventLoopGroup();
     private final EventLoopGroup workerGroup = new NioEventLoopGroup();
     private final ConcurrentMap<String, MessageHandler> handlers = new ConcurrentHashMap<>();
-    private Cache<Long, AsyncResponse<?>> responseFutures;
-    private final Endpoint localEp;
+    private final Cache<Long, AsyncResponse<?>> responseFutures = CacheBuilder.newBuilder()
+            .maximumSize(100000)
+            .weakValues()
+            // TODO: Once the entry expires, notify blocking threads (if any).
+            .expireAfterWrite(10, TimeUnit.MINUTES)
+            .build();
+    private final GenericKeyedObjectPool<Endpoint, Channel> channels
+            = new GenericKeyedObjectPool<Endpoint, Channel>(new OnosCommunicationChannelFactory());
 
     protected Serializer serializer;
 
@@ -65,15 +71,8 @@ public class NettyMessagingService implements MessagingService {
     }
 
     public void activate() throws Exception {
-        channels = new GenericKeyedObjectPool<Endpoint, Channel>(new OnosCommunicationChannelFactory());
         channels.setTestOnBorrow(true);
         channels.setTestOnReturn(true);
-        responseFutures = CacheBuilder.newBuilder()
-                .maximumSize(100000)
-                .weakValues()
-                // TODO: Once the entry expires, notify blocking threads (if any).
-                .expireAfterWrite(10, TimeUnit.MINUTES)
-                .build();
         startAcceptingConnections();
     }
 
@@ -145,7 +144,8 @@ public class NettyMessagingService implements MessagingService {
     private void startAcceptingConnections() throws InterruptedException {
         ServerBootstrap b = new ServerBootstrap();
         b.option(ChannelOption.WRITE_BUFFER_HIGH_WATER_MARK, 32 * 1024);
-        b.option(ChannelOption.WRITE_BUFFER_LOW_WATER_MARK, 32 * 1024);
+        b.option(ChannelOption.WRITE_BUFFER_LOW_WATER_MARK, 8 * 1024);
+        // TODO: Need JVM options to configure PooledByteBufAllocator.
         b.option(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT);
         b.group(bossGroup, workerGroup)
             .channel(NioServerSocketChannel.class)
@@ -172,19 +172,18 @@ public class NettyMessagingService implements MessagingService {
 
         @Override
         public Channel makeObject(Endpoint ep) throws Exception {
-            Bootstrap b = new Bootstrap();
-            b.option(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT);
-            b.option(ChannelOption.WRITE_BUFFER_HIGH_WATER_MARK, 32 * 1024);
-            b.option(ChannelOption.WRITE_BUFFER_LOW_WATER_MARK, 32 * 1024);
-            b.group(workerGroup);
+            Bootstrap bootstrap = new Bootstrap();
+            bootstrap.option(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT);
+            bootstrap.option(ChannelOption.WRITE_BUFFER_HIGH_WATER_MARK, 32 * 1024);
+            bootstrap.option(ChannelOption.WRITE_BUFFER_LOW_WATER_MARK, 8 * 1024);
+            bootstrap.group(workerGroup);
             // TODO: Make this faster:
             // http://normanmaurer.me/presentations/2014-facebook-eng-netty/slides.html#37.0
-            b.channel(NioSocketChannel.class);
-            b.option(ChannelOption.SO_KEEPALIVE, true);
-            b.handler(new OnosCommunicationChannelInitializer());
-
+            bootstrap.channel(NioSocketChannel.class);
+            bootstrap.option(ChannelOption.SO_KEEPALIVE, true);
+            bootstrap.handler(new OnosCommunicationChannelInitializer());
             // Start the client.
-            ChannelFuture f = b.connect(ep.host(), ep.port()).sync();
+            ChannelFuture f = bootstrap.connect(ep.host(), ep.port()).sync();
             return f.channel();
         }
 
@@ -201,12 +200,15 @@ public class NettyMessagingService implements MessagingService {
 
     private class OnosCommunicationChannelInitializer extends ChannelInitializer<SocketChannel> {
 
+        private final ChannelHandler dispatcher = new InboundMessageDispatcher();
+        private final ChannelHandler encoder = new MessageEncoder(serializer);
+
         @Override
         protected void initChannel(SocketChannel channel) throws Exception {
             channel.pipeline()
-                .addLast("encoder", new MessageEncoder(serializer))
+                .addLast("encoder", encoder)
                 .addLast("decoder", new MessageDecoder(NettyMessagingService.this, serializer))
-                .addLast("handler", new InboundMessageDispatcher());
+                .addLast("handler", dispatcher);
         }
     }
 
@@ -222,10 +224,11 @@ public class NettyMessagingService implements MessagingService {
 
         @Override
         public void run() {
-            channel.writeAndFlush(message);
+            channel.writeAndFlush(message, channel.voidPromise());
         }
     }
 
+    @ChannelHandler.Sharable
     private class InboundMessageDispatcher extends SimpleChannelInboundHandler<InternalMessage> {
 
         @Override
@@ -248,7 +251,6 @@ public class NettyMessagingService implements MessagingService {
             handler.handle(message);
         }
 
-
         @Override
         public void exceptionCaught(ChannelHandlerContext context, Throwable cause) {
             context.close();