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Netty 4 Overview (Obsolete)

Trustin Lee
February 27, 2013

Netty 4 Overview (Obsolete)

UPDATE: This presentation is out-of-date. We changed a lot of things in the public API since then.

Netty is a Java asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. It powers many large scale services built on top of JVM such as Twitter.

This talk will provide an overview of Netty 4, the major backward-incompatible update against the version 3, from basic constructs to a working example. It's not necessarily for those who are familiar with the previous versions on Netty.

Trustin Lee

February 27, 2013
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Transcript

  1. What is Netty? an asynchronous event-driven network application framework for

    rapid development of maintainable high performance protocol servers & clients
  2. Asynchronous Channel channel = ... ChannelFuture f = channel.write(message); f.addListener((f)

    -> { if (f.isSuccess()) { f.channel().write(nextMessage); // Async } else { f.cause().printStackTrace(); f.channel().close(); // Async } });
  3. Synchrony via Asynchrony ChannelFuture f = channel.write(message); try { f.sync()

    .channel().write(nextMessage).sync(); } finally { f.channel().close(); }
  4. Event-driven class MyInboundMessageListener extends ChannelInboundMessageHandlerAdapter <MyInboundMessage> { @Override void messageReceived(

    ChannelHandlerContext ctx, MyInboundMessage msg) { MyOutboundMessage res = ...; ctx.write(res); } }
  5. Available events • channelRegistered/Active • inboundBufferUpdated ◦ Most handlers have

    its own inbound buffer. ◦ Much less GC pressure than generating event objects per message ◦ CIMHAdapter.inboundBufferUpdated() invokes messageReceived() • channelInactive/Unregistered • exceptionCaught (Throwable) • userEventTriggered (Object)
  6. ChannelInboundByteHandlerAdapter abstract class ChannelInboundByteHandlerAdapter ... { ByteBuf newInboundBuffer(ChannelHandlerContext ctx) {

    return ctx.alloc().buffer(); } void freeInboundBuffer(ChannelHandlerContext ctx) { ctx.inboundByteBuffer().release(); } final void inboundBufferUpdated(ChannelHandlerContext ctx) { inboundBufferUpdated(ctx, ctx.inboundByteBuffer()); } abstract void inboundBufferUpdated(ctx, ByteBuf in); ... }
  7. ByteBufAllocator • "ctx.alloc().buffer()" • The default: PooledByteBufAllocator ◦ Pure Java

    jemalloc impl with some twist ◦ Beats JVM by not filling with NUL(0) ◦ Takes advantage of sun.misc.Unsafe to: ▪ Deallocate direct buffers timely ▪ Access direct buffers directly (+10% faster) ◦ Reference-counted ▪ "buf.release()" and "buf.retain()" ▪ Sampled leak detection enabled by '-D' flag
  8. Pipeline: List<ChannelHandler> ChannelPipeline p = ch.pipeline(); p.addLast( new HttpRequestDecoder(), //

    IB new HttpResponseEncoder(), // OM new MyHttpServiceHandler()); // IM p.addFirst(new SslHandler(...)); // IB //+OB
  9. Pipeline: dynamic manipulation class HttpAndHttpsHandler extends ChannelInboundByteHandlerAdapter { void inboundBufferUpdated(ctx,

    inBuf) { if (isHttp(inBuf)) { addHttpHandlers(ctx, inBuf); } else if (isSsl(inBuf)) { addSslHandler(ctx, inBuf); } else { ctx.close(); // Unknown protocol } }
  10. Pipeline: staged event threading EventExecutorGroup group = new DefaultEventExecutorGroup(16); ChannelPipeline

    p = channel.pipeline(); p.addLast( new RedisRequestDecoder(), // IB new RedisResponseEncoder()); // OM p.addLast( group, new RedisServiceHandler()); // IM
  11. EventExecutor and EventLoop • EventLoop ◦ performs actual I/O ◦

    triggers an event to a pipeline ◦ receives an operation from a pipeline ◦ performs arbitrary tasks submitted by user • EventExecutor ◦ EventLoop minus I/O ◦ Usually specified as an arg to ChannelPipeline. add*()
  12. Factorial example • Sends sequential integers to multiply them •

    Codec ◦ NumberEncoder ◦ BigIntegerDecoder • Server ◦ FactorialServerHandler ◦ FactorialServerInitializer ◦ FactorialServer • Client ◦ FactorialClientHandler ◦ FactorialClientInitializer ◦ FactorialClient