1. Building scalable network applications
with Netty
Jaap ter Woerds
@jaaptw
XMS pin: EBDDFF9A

2. The trouble with synchronous IO

3. The trouble with synchronous IO

4. The trouble with synchronous IO

5. Creating your custom server

6. Creating your custom server

7. Netty?
Unified, asynchronous programming model. All
IO operations return immediately.

8. Netty?
Channel channel =..
channel.write(myMsg).addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
if(future.isSuccess()){
// Business as usual
} else{
// Handle failure
}
}
});

9. Netty?
Networking application framework with a modular
architecture and quite some ready reusable
components.

10. When should I care about this?
Custom servers / networking applications /
proxies
High concurrency

11. Netty concepts

12. Netty concepts
ByteBuf
random accessable sequence of bytes
Abstraction over plain byte arrays and NIO buffers

13. Netty concepts
ByteBuf
Use: encoding and decoding data
ByteBuf b = .
b.writeInt(3).writeBoolean(true);

14. Netty concepts
Channel
Link ('connection') to a resource that provides IO operations like read /
write

15. Netty concepts
Channel
Channel c = ..;
c.write(myMsg).addListener(CLOSE);

16. Netty concepts
ChannelHandler
IO event listener,handles outbound and / or inbound events.

17. Netty concepts
ChannelInboundHandler
Defines listener methods for incoming IO events

18. Netty concepts
ChannelInboundHandler
channelActive(ChannelHandlerContext ctx)
channelRead(ChannelHandlerContext ctx, Object msg)
channelReadComplete(ChannelHandlerContext ctx)
channelInactive(ChannelHandlerContext ctx)
....

19. Netty concepts
ChannelOutboundHandler
Defines listener methods for outgoing IO events

20. Netty concepts
ChannelOutboundHandler
write(ChannelHandlerContext ctx, Object msg, ChannelPromise..)
flush(ChannelHandlerContext ctx)

21. Netty concepts
ChannelPipeline
A List of ChannelHandlers that process incoming and outgoing events
in a specific order

22. Netty concepts
ChannelInitializer
Configures the pipeline for a Channel. In fact, a special case of
ChannelInboundHandler which creates the handlers for a channel
whenerver a new channel is registered.

23. Netty concepts
ChannelInitializer
Configures the pipeline for a Channel. In fact, a special case of
ChannelInboundHandler which creates the handlers for a channel
whenerver a new channel is registered.

24. Netty concepts
ChannelInitializer
@Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
// Decoders
pipeline.addLast("frameDecoder", new LineBasedFrameDecoder(MAX_LENGTH));
pipeline.addLast("stringDecoder", STRING_DECODER);
pipeline.addLast("moderatorHandler", moderatorHandler);
pipeline.addLast("chatServerHandler", chatServerHandler);
// Encoder
pipeline.addLast("stringEncoder", STRING_ENCODER);
}

25. Netty concepts
Bootstrap
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, BACKLOG)
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(channelInitializer);
ChannelFuture f = b.bind(port).sync();
f.channel().closeFuture().sync();

26. Netty architecture
Chain of responsibility
Incoming data flow through the ChannelPipeline
- Framing ByteBuf
- Decode frames
- Decode frames in DTOs/POJOs

27. Netty architecture

28. Netty components
Out of the box support for:
Streaming compression Zlib
SSL stream encryption
HTTP
WebSockets
ProtocolBuffer

29. XMS server protocol layer

30. Example SSE / CORS

31. Example SSE / CORS
In the last handler we deal with normal POJO and handle an
incoming request without actually caring about the connection layer!
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
IncomingMessagePojo m = (IncomingMessagePojo) msg;
handle(m);// Login / Send a text message/ Handle create group
}

32. Example SSE / CORS

33. Thank you!
Example code:
https://github.com/jaapterwoerds/jfall-netty4
Further reading:
https://nettio.io
http://xms.me
http://tech.ebuddy.com