netty

1. Netty로 소켓 통신 개발

2. 전통적인 소켓 통신 프로그래밍

3. Java에서 구현시

4. 이러한 구현 방식은?
• Blocking IO 방식
• "Blocking" means that the caller waits until
the callee finishes its processing. For
instance, a "blocking read" from a socket
waits until there is data to return; a "non-
blocking" read does not, it just returns an
indication (usually a count) of whether
there was something read

6. 요즘의 주된 방식은?
Non blocking IO & Async

8. multiplexing i/o

10. Non blocking socket 종류
• select
• poll
• epoll
• iocp

11. 자바에서의 NIO
• Channel
• SocketChannel
• SelectableChannel
• ServerSocketChannel

13. Asynchronous I/O
• AsynchronousChannel
• AsynchronousSocketChannel
• AsynchronousServerSocketChannel
• AsynchronousFileChannel

14. Netty?
• Java Network framework
• Asynchronous & event driven
• Well defined event model & thread Model
• JDK 1.5 dependency free

15. Feature
• Asynchronous!
• Simple and unified API!
• High-Performing!
• Listeners and Callbacks supported!
• Zero-file-copy!
• Buffer Pooling!
• Gathering / Scattering
• ... and many more

16. Netty 구조

21. Support Protocol
• TCP
• UDP
• SCTP
• Serial
• …

22. © http://www.flickr.com/photos/bdesham/2432400623/
ChannelHandler

23. Network
BootStrap
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ChannelPipeLine
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!Decoder/Encoder
ReplayDecoder
ChannelHandler
:
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ChannelHandler 구조
ByteBuf

24. ChannelHandler
• Thread safe
• EventExecutor에 의해서 호출된
• InBound & OutBind Handler 가 존재함
• User는 Handler만 추가해서 Business login 구현가
능

25. 기본 제공 Handler
• IdleEventHandler
• StringDecoder/StringEncoder
• ReplayDecoder
• ….
일반적으로는 SimpleChannelInboundHandler 만 사용해도 가능

26. ChannelHandlerAdapter

27. http://www.flickr.com/photos/rickz/2113212191/
ChannelPipeLine

28. ChannelPipeline
• linux에서 사용하는 Pipe명령과 동일한 구조
• 모든 이벤트는 이것을 통해서 이동함.
• Channel과 ChannelPipeline은 1:1 매핑되어 있음.

29. Event-loop
• Reactor pattern이라고 함
• single thread 에 event를 등록하고 발생하는 이벤트를 디스
패치 하는 패턴
• 이런 패턴을 적용한 애플리케이션
• IOS
• GNOME
• Winmain

30. Event-loop in Netty
• One-to-Many relation between EventLoop and Channel
• Process "events" and hand over work to the
ChannelPipeline
• All tasks executed in Eventloop
• Eventloop로 업무나 추가처리를 할 수 있음
• synchronization 처리 필요없음
• blocking 안됨

31. Eventloop 작동방식

32. DATA CONTAINER
http://normanmaurer.me/presentations/2013-wjax-netty/images/containers.jpg
“ByteBuf == ByteBuffer on steroids!”

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

34. ByteBufferAllocator
https://blog.twitter.com/2013/netty-4-at-twitter-reduced-gc-overhead

35. Echo Server Demo

36. Q & A

37. 참고자료
• http://normanmaurer.me/presentations/2013-
wjax-netty
• http://www.ibm.com/developerworks/library/j-
zerocopy/
• http://netty.io