From f247130c0adff57400fbf31639f78b1194661c7f Mon Sep 17 00:00:00 2001 From: asahi Date: Mon, 20 Jan 2025 14:33:21 +0800 Subject: [PATCH] =?UTF-8?q?=E9=98=85=E8=AF=BBnetty=20pipeline=E6=96=87?= =?UTF-8?q?=E6=A1=A3?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- netty/netty-doc.md | 130 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 130 insertions(+) create mode 100644 netty/netty-doc.md diff --git a/netty/netty-doc.md b/netty/netty-doc.md new file mode 100644 index 0000000..6991a17 --- /dev/null +++ b/netty/netty-doc.md @@ -0,0 +1,130 @@ +# netty document +## ChannelPipeline + I/O Request + via Channel or + ChannelHandlerContext + | + +---------------------------------------------------+---------------+ + | ChannelPipeline | | + | \|/ | + | +---------------------+ +-----------+----------+ | + | | Inbound Handler N | | Outbound Handler 1 | | + | +----------+----------+ +-----------+----------+ | + | /|\ | | + | | \|/ | + | +----------+----------+ +-----------+----------+ | + | | Inbound Handler N-1 | | Outbound Handler 2 | | + | +----------+----------+ +-----------+----------+ | + | /|\ . | + | . . | + | ChannelHandlerContext.fireIN_EVT() ChannelHandlerContext.OUT_EVT()| + | [ method call] [method call] | + | . . | + | . \|/ | + | +----------+----------+ +-----------+----------+ | + | | Inbound Handler 2 | | Outbound Handler M-1 | | + | +----------+----------+ +-----------+----------+ | + | /|\ | | + | | \|/ | + | +----------+----------+ +-----------+----------+ | + | | Inbound Handler 1 | | Outbound Handler M | | + | +----------+----------+ +-----------+----------+ | + | /|\ | | + +---------------+-----------------------------------+---------------+ + | \|/ + +---------------+-----------------------------------+---------------+ + | | | | + | [ Socket.read() ] [ Socket.write() ] | + | | + | Netty Internal I/O Threads (Transport Implementation) | + +-------------------------------------------------------------------+ + +如上图所示，i/o event将会被`ChannelInboundHandler`或`ChannelOutboundHandler`处理，并且通过调用`ChannelHandlerContext`中的event propagation method（触发事件传播的方法）来进行转发。 + +常见的event propagation method如下，例如`ChannelHandlerContext.write(Object)`。 + +### inbound event +inbound event会通过inbound handler自底向上的进行处理，例如上图的左边部分所示。inbound handler通常处理由io thread产生的inbound data，inbound则是通常从remote peer读取。 + +> 如果inbound event传播到高于top inbound handler，那么该event将会被丢弃。 + +### outbound event +outbound event会按照自顶向下的顺序被outbound进行处理，outbound handler通常产生outbound traffic或对outbound traffic进行处理。 + +> 如果outbound event传播到低于bottom outbound handler, 其会直接被channel关联的io线程处理。 + +> 通常，io thread会执行实际的输出操作，例如`SocketChannel.write(ByteBuffer)`。 + +### pipeline处理顺序 +例如，按照如下顺序项pipeline中添加handler时， +```java + ChannelPipeline p = ...; + p.addLast("1", new InboundHandlerA()); + p.addLast("2", new InboundHandlerB()); + p.addLast("3", new OutboundHandlerA()); + p.addLast("4", new OutboundHandlerB()); + p.addLast("5", new InboundOutboundHandlerX()); +``` +#### inbound +对于inbound event，handler的执行顺序为`1,2,3,4,5` + +但由于`3,4`没有实现ChannelInboundHandler，故而Inbound event会跳过`3,4` handler，实际Inbound event的handler顺序为`1,2,5` + +#### outbound +对于outbound event，handler的执行顺序为`5,4,3,2,1` + +对于outbound evnet，由于`1,2`并没有实现ChannelOutboundHandler，故而outbound event的handler顺序为`5,4,3`。 + +> inbound顺序和pipeline handler的添加顺序相同，outbound顺序和pipeline handler添加顺序相反。 + +### 将event转发给下一个handler +如上图所示，再handler中必须调用`ChannelHandlerContext`中的event propagation method来将event转发给下一个handler。`event propagation event`包括的方法如下： + +#### Inbound event propagation method +- ChannelHandlerContext.fireChannelRegistered() +- ChannelHandlerContext.fireChannelActive() +- ChannelHandlerContext.fireChannelRead(Object) +- ChannelHandlerContext.fireChannelReadComplete() +- ChannelHandlerContext.fireExceptionCaught(Throwable) +- ChannelHandlerContext.fireUserEventTriggered(Object) +- ChannelHandlerContext.fireChannelWritabilityChanged() +- ChannelHandlerContext.fireChannelInactive() +- ChannelHandlerContext.fireChannelUnregistered() + +#### Outbound event propagation method +- ChannelHandlerContext.bind(SocketAddress, ChannelPromise) +- ChannelHandlerContext.connect(SocketAddress, SocketAddress, ChannelPromise) +- ChannelHandlerContext.write(Object, ChannelPromise) +- ChannelHandlerContext.flush() +- ChannelHandlerContext.read() +- ChannelHandlerContext.disconnect(ChannelPromise) +- ChannelHandlerContext.close(ChannelPromise) +- ChannelHandlerContext.deregister(ChannelPromise) + +### build pipeline +在一个pipeline中，应该包含一个或多个ChannelHandler用于接收IO事件（read）和请求IO操作（write and close）。例如，一个典型的server其channel的pipeline中应该包含如下handler： +- protocol decoder：将二进制数据转化为java object +- protocol encoder：将java object转化为二进制数据 +- business logic handler：执行实际业务操作 + +构建pipeline示例如下： +```java + static final EventExecutorGroup group = new DefaultEventExecutorGroup(16); + ... + ChannelPipeline pipeline = ch.pipeline(); + + pipeline.addLast("decoder", new MyProtocolDecoder()); + pipeline.addLast("encoder", new MyProtocolEncoder()); + + // Tell the pipeline to run MyBusinessLogicHandler's event handler methods + // in a different thread than an I/O thread so that the I/O thread is not blocked by + // a time-consuming task. + // If your business logic is fully asynchronous or finished very quickly, you don't + // need to specify a group. + pipeline.addLast(group, "handler", new MyBusinessLogicHandler()); +``` +当为BusinessLogicHandler指定DefaultEventExecutorGroup时，虽然会将操作从EventLoop中卸载，但是其针对每个ChannelHandlerContext仍然是串行进行处理的。故而，串行处理可能仍然会导致性能瓶颈。如果在用例场景下顺序不太重要时，可以考虑使用`UnorderedThreadPoolEventExecutor`来最大化任务的并行执行。 + +### ThreadSafety +channelhandler可以在任何时刻添加到pipeline或从pipeline中移除，ChannelPipeline是线程安全的。例如，可以在交换敏感信息前添加encryption handler并且在交换完信息后将encryption handler移除。 +