add netty readme markdown file in spring boot sample

Author: ipipman

springboot-netty-sample/README.md

@@ -4,6 +4,8 @@
 
 <img src="https://tva1.sinaimg.cn/large/008i3skNly1gyol111yspj31aa0jggob.jpg" alt="image-20220124110420220" width="700" align="left" />
 
+
+
 ##### Netty并不是只支持过NIO，但是不建议（depercate）阻塞I/O（BIO/OIO）
 
 - 连接数高的情况下：阻塞 -> 消耗源、效率低
@@ -31,6 +33,8 @@ BIO 下是 Thread-Per-Connection
 
 <img src="https://tva1.sinaimg.cn/large/008i3skNly1gyolp1ody6j31fy0kggpn.jpg" alt="image-20220124112504631" width="700" align="left"/>
 
+
+
 ***Thread-Per-Connection：对应每个连接都有1个线程处理，1个线程同时处理：读取、解码、计算、编码、发送***
 
 
@@ -39,6 +43,8 @@ NIO 下是 Reactor
 
 <img src="https://tva1.sinaimg.cn/large/008i3skNly1gyolp5zqpaj316w0pmadn.jpg" alt="image-20220124112753682" width="700"  align="left" >
 
+
+
 ***Reactor 多线程模式，由多个线程负责：读取、发送，由线程池负责处理：解码、计算、编码*** 
 
 ***Reactor 主从多线程模式，由单独mainReactor 单线程负责接收请求，subReactor和 Reactor 多线程模式一致***
@@ -89,6 +95,146 @@ serverBootStrap.group(bossGroup, workerGroup);
 
 
 
+##### Netty 支持主从 Reactor 源码分析
+
+1.初始化 Main EventLoopGroup
+
+```java
+public abstract class AbstractBootstrap<B extends AbstractBootstrap<B, C>, C extends Channel> implements Cloneable {
+
+  	// main Event Loop Group
+    volatile EventLoopGroup group;
+  	
+  	....
+  	
+    // 初始化 mian Event Loop Group 方法
+    public B group(EventLoopGroup group) {
+        ObjectUtil.checkNotNull(group, "group");
+        if (this.group != null) {
+            throw new IllegalStateException("group set already");
+        }
+        this.group = group;
+        return self();
+    }
+  
+  ....
+}
+```
+
+2. 初始化 Worker EventLoopGroup
+
+```java
+public class ServerBootstrap extends AbstractBootstrap<ServerBootstrap, ServerChannel> {
+  	
+  	// woker Events Loop Group
+	  private volatile EventLoopGroup childGroup;
+  	.....
+      
+		public ServerBootstrap group(EventLoopGroup parentGroup, EventLoopGroup childGroup) {
+        super.group(parentGroup);
+        ObjectUtil.checkNotNull(childGroup, "childGroup");
+        if (this.childGroup != null) {
+            throw new IllegalStateException("childGroup set already");
+        }
+        // 初始化 worker Event Loop Group 方法
+        this.childGroup = childGroup;
+        return this;
+    }
+  
+  	.... 
+}
+```
+
+3. MainEventLoopGroup 和 WorkerEventLoop 绑定# bind()，并实现新建和初始化 SocketChannel 绑定到 MainEventLoopGroup中
+
+```java
+// 绑定 地址：端口   
+public ChannelFuture bind(SocketAddress localAddress) {
+   validate();
+   return doBind(ObjectUtil.checkNotNull(localAddress, "localAddress"));
+}
+
+// 绑定逻辑 
+private ChannelFuture doBind(final SocketAddress localAddress) {
+  // 初始化 & 注册 MainEventLoopGroup
+  final ChannelFuture regFuture = initAndRegister();
+  final Channel channel = regFuture.channel();
+  ....
+}
+
+// 初始化 & 注册 MainEventLoopGroup
+final ChannelFuture initAndRegister() {
+  Channel channel = null;
+  try {
+    // 创建新的 ServerSocketChannel 
+    channel = channelFactory.newChannel();
+    // 初始化 ServerSocketChannel 中的 Handler
+    init(channel);
+  } catch (Throwable t) {
+    if (channel != null) {
+      // channel can be null if newChannel crashed (eg SocketException("too many open files"))
+      channel.unsafe().closeForcibly();
+      // as the Channel is not registered yet we need to force the usage of the GlobalEventExecutor
+      return new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE).setFailure(t);
+    }
+    // as the Channel is not registered yet we need to force the usage of the GlobalEventExecutor
+    return new DefaultChannelPromise(new FailedChannel(), GlobalEventExecutor.INSTANCE).setFailure(t);
+  }
+
+  // 将 ServerSocketChannel 注册到 MainEventLoop 中
+  // 因为端口和地址 只有1个，channel只能被注册一次，所以 MainEventLoopGroup 是单线程的
+  ChannelFuture regFuture = config().group().register(channel);
+  if (regFuture.cause() != null) {
+    if (channel.isRegistered()) {
+      channel.close();
+    } else {
+      channel.unsafe().closeForcibly();
+    }
+  }
+  ...
+}  
+
+```
+
+4. WorkerEventLoopGroup 和 SocketChannel 绑定关系
+
+```java
+private static class ServerBootstrapAcceptor extends ChannelInboundHandlerAdapter {
+  @Override
+  @SuppressWarnings("unchecked")
+  public void channelRead(ChannelHandlerContext ctx, Object msg) {
+    // 每次读取都是一个 SocketChannel
+    final Channel child = (Channel) msg;
+
+    child.pipeline().addLast(childHandler);
+
+    setChannelOptions(child, childOptions, logger);
+
+    for (Entry<AttributeKey<?>, Object> e: childAttrs) {
+      child.attr((AttributeKey<Object>) e.getKey()).set(e.getValue());
+    }
+
+    try {
+      // 将 SocketChannel 注册到 workerEventLoopGroup中
+      childGroup.register(child).addListener(new ChannelFutureListener() {
+        @Override
+        public void operationComplete(ChannelFuture future) throws Exception {
+          if (!future.isSuccess()) {
+            forceClose(child, future.cause());
+          }
+        }
+      });
+    } catch (Throwable t) {
+      forceClose(child, t);
+    }
+  }  
+}
+```
+
+
+
+
+
 #### 3.Netty 粘包/半包解决方案
 
 关于半包的主要原因：
@@ -100,6 +246,8 @@ serverBootStrap.group(bossGroup, workerGroup);
 
 
 
+
+
 关于粘包的主要原因：
 
 - 发送方每次写入数据 > 套接字缓冲区大小
@@ -162,3 +310,5 @@ TCP 是流式协议，消息无边界
 
 
 
+
+