Netty - Network - Application development the easy way

Network - Application development the easy way

http://netty.io

https://github.com/netty/netty

@netty_project

Norman Maurer

Red Hat (JBoss) - EAP Core Team
Former contractor for Apple Inc
Author - Netty in Action
Apache Software Foundation Member
Netty / Vert.x Core-Developer and all things NIO
Java and Scala
Twitter: @normanmaurer
Github: https://github.com/normanmaurer

What is NETTY ?

Netty is a NIO client server framework which enable quick and easy development of network applications such as protocol servers and clients...

YET ANOTHER Network FrameWORK ?

YES!

@!# WTF, why should I care ?

Features

Asynchronous
Simple and unified API
High-Performing
Listeners and Callbacks supported
Zero-file-copy
Buffer Pooling
Gathering / Scattering

... and many more

Asynchronous, what does this mean ?

Asynchronous...

I/O Operations don't block at all!
Get notified once the operation completes
Be able to share one Thread across many connections

As waiting is b0ring....

But synchronous / blocking IO served me well! Again, why should I care ?

Blocking-IO may not SCALE!

Usually a Thread takes memory from 256kb to 1mb for the stack space!

Good luck with serving 1 million concurrent connections

Ouch....

Netty to the rescue

Asynchronous in action

    Channel channel = ...
    ChannelFuture cf = channel.writeAndFlush(data);
    cf.addListener(
        new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture future)
                throws Exception {
                if(!future.isSuccess() {
                    future.cause().printStacktrace();
                    ...
                }
                ...
            }
        });
    ...
    // or block and wait for completion if you really need!
    cf.sync();

Transports

NIO
OIO
Local
Embedded

And more to come ....

Supported protocols

TCP
UDP
SCTP*
UDT
Serial

* Only supported on linux

Simple state Model

State Flow

Data Container

ByteBuf == ByteBuffer on steroids!

ByteBuf

Separate index for reader/writer
CompositeByteBuf
Direct and Heap implementations
Resizable with max capacity
Support for reference-counting
Method-Chaining

    ByteBuf buf = ...;
    buf.writeInt(1).writeBytes(data).writeBoolean(true)...

ByteBufAllocator

Pooling or not pooling....

Channelhandler

Users building blocks!

ChannelHandler

Your business logic needs a place, and this is where it belongs too

ChannelHandler Facts

Inbound vs. Outbound
Always called by the assigned EventExecutor
Type-safe*

Example use cases

Convert data a.k.a Encoder / Decoder
Business-Logic
Handle state changes

Provided codecs

We have a lot of them!

Provided Codecs

HTTP
Websockets
SPDY
Serialization
JBoss Marshalling
Protobufs
SSL
Zlib

Provided Codecs - The future

DNS
Memcached Binary
SockJS

Adapters

Makes your life easier

ChannelInboundHandlerAdapter
ChannelOutboundHandlerAdapter
SimpleChannelInboundHandler

Adapter in Action

    @Sharable
    public class  Echo4ServerHandler extends 
            ChannelInboundHandlerAdapter {        
        @Override 
        public void channelRead(ChannelHandlerContext ctx,
                Object msg) {
            ctx.writeAndFlush(msg);
        }
        
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx,
                Throwable cause) {
            cause.printStacktrace();
            ctx.close();
        }
    }

Decoder

ByteToMessageDecoder
MessageToMessageDecoder

Encoder

MessageToByteEncoder
MessageToMessageEncoder

Hybrids

ByteToByteCodec
ByteToMessageCodec
MessageToMessageCodec

Other Often useful Decoders

ReplayDecoder
FixedLengthFrameDecoder
LengthFieldBasedFrameDecoder
LineBasedFrameDecoder
DelimiterBasedFrameDecoder

ChannelPipeline

The home for all your ChannelHandlers

ChannelPipeline

Holds the ChannelHandlers for a Channel
All events will get passed through it
On the fly modification
One-to-one relation between Channel and ChannelPipeline

ChannelPipeline

Kind of a unix-pipe-like thing...

$ echo "Netty is shit...." | sed -e 's/is /is the /'
                    Netty is the shit....

You see, everything is adjustable!

Adding ChannelHandlers

    Channel ch = ...;
    ChannelPipeline p = ch.pipeline();
    EventExecutor e1 = new DefaultEventExecutor(16);
    EventExecutor e2 = new DefaultEventExecutor(8);

    // Executed in EventLoop Thread
    p.addLast(new MyProtocolCodec());

    // Executed in one of the Threads of e1
    p.addLast(e1, new MyDatabaseAccessingHandler());

    // Executed in one of the Threads of e1
    p.addLast(e2, new MyHardDiskAccessingHandler());

Event-Loop

Someone needs to do the heavy work!

Event-loop

One-to-Many relation between EventLoop and Channel
Process "events" and hand over work to the ChannelPipeline

All Tasks executed in Event-Loop!

No need to worry about synchronization

Repeat with me:

I promise to never block the Event-Loop!

EventLoop Hierarchy

All the ScheduleExecutorService goodies for free!

EventLoop - How does it work

Run a Task in the EventLoop

    public class MyHandler extends 
            ChannelOutboundHandlerAdapter {
        @Override
        public void write(ChannelHandlerContext ctx,
                Object msg, ChannelPromise promise) {
            ctx.write(msg, promise);
        
            if (!promise.isDone() {
                // schedule task for in 30 seconds
                ctx.executor().schedule(new MyWriteTimeoutTask(
                    promise), 30, TimeUnit.SECONDS);
            }
            // Run an arbitrary task from an I/O thread.
            ctx.executor().execute(new Runnable() { ... });
        }
    }

Bootstrap your application

It's time to accept some real traffic

Bootstrap

Fluent-API a.k.a DSL
Graceful shutdown
Lightweight

Bootstrap a Server

    ServerBootstrap b = new ServerBootstrap();
    EventLoopGroup group = new NioEventLoopGroup(numThreads);
    try {
        b.group(group, group))
            .channel(NioServerSocketChannel.class)
            .localAddress(new InetSocketAddress(port))
            .childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                public void initChannel(SocketChannel ch) {
                    ch.pipeline().addLast(new YourChannelHandler());
                }
            });
        ChannelFuture f = b.bind().sync();
        f.channel().closeFuture().sync();
    } finally {
        group.shutdownGracefully();
    }

Bootstrap a Client

    Bootstrap b = new Bootstrap();
    EventLoopGroup group = new NioEventLoopGroup(numThreads);
    try { 
        b.group(group)
            .channel(NioSocketChannel.class)
            .remoteAddress(new InetSocketAddress("10.0.0.1", 25))
            .handler(new ChannelInitializer<SocketChannel>() {            
                @Override
                public void initChannel(SocketChannel ch) {  
                    ch.pipeline().addLast(new YourChannelHandler());
                }
            });
        ChannelFuture f = b.connect().sync();
        f.channel().closeFuture().sync();
    } finally {
        group.shutdownGracefully();
    }

General

ASL2 license
Hosted at Github
Community-driven

Companies

Red Hat
Twitter
Facebook
Firebase
Urban Airship
LinkedIn
Samsung
Boundary

And many more...

(Opensource) Projects

Vert.x
HornetQ
Infinispan
Play Framework*
Finangle
Apache Cassandra
Minecraft

And again many more....

Things to come

Chained ChannelPipelines
Native edge-triggered Transport*
Lambda support

Other NIO Frameworks

Apache MINA
Grizzly
Akka IO
HawtDispatch*
JBoss XNIO*

It's OpenSource - Contribute now!

Get Involved

Mailinglist

https://groups.google.com/forum/#!forum/netty

IRC

#netty irc.freenode.org

Website

http://netty.io

GitHub

https://github.com/netty/netty/

Too Low Level ?

You may like Vert.x which is based on Netty!

Not enough info?

You may want to buy my book...

http://www.manning.com/maurer/

Norman Maurer

What is NETTY ?

YET ANOTHER Network FrameWORK ?

@!# WTF, why should I care ?

Features

Features

Asynchronous, what does this mean ?

Asynchronous...

Blocking-IO may not SCALE!

Good luck with serving 1 million concurrent connections

Netty to the rescue

Asynchronous in action

Transports

Supported protocols

Simple state Model

State Flow

Data Container

ByteBuf

ByteBufAllocator

Channelhandler

ChannelHandler

ChannelHandler Facts

Example use cases

Provided codecs

Provided Codecs

Provided Codecs - The future

Adapters

Adapter in Action

Decoder

Encoder

Hybrids

Other Often useful Decoders

ChannelPipeline

ChannelPipeline

ChannelPipeline

Adding ChannelHandlers

Event-Loop

Event-loop

EventLoop Hierarchy

EventLoop - How does it work

Run a Task in the EventLoop

Bootstrap your application

Bootstrap

Bootstrap a Server

Bootstrap a Client

General

Companies

(Opensource) Projects

Things to come

Other NIO Frameworks

It's OpenSource - Contribute now!

Get Involved

Too Low Level ?

Not enough info?

Questions please!

Thanks!