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[pull] master from ipipman:master #25

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pull merged 1 commit into Mu-L:master from ipipman:master
Jan 24, 2022
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150 changes: 150 additions & 0 deletions springboot-netty-sample/README.md
View file Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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***


Expand All @@ -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***
Expand Down Expand Up @@ -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:
Expand All @@ -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
Expand Down Expand Up @@ -162,3 +310,5 @@ TCP 是流式协议,消息无边界





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