深入浅出Netty之二 server启动

以netty提供的echo server作为分析入口，echoServer代码:

public void run() {  
        // 构造NioServerSocketChannelFactory，初始化bootstrap  
        ServerBootstrap bootstrap = new ServerBootstrap(  
                new NioServerSocketChannelFactory(  
                        Executors.newCachedThreadPool(),  
                        Executors.newCachedThreadPool()));  
  
        // 创建一个自定义的PipelineFactory  
        bootstrap.setPipelineFactory(new ChannelPipelineFactory() {  
            public ChannelPipeline getPipeline() throws Exception {  
                return Channels.pipeline(new EchoServerHandler());  
            }  
        });  
  
        // 开始bind端口，启动server  
        bootstrap.bind(new InetSocketAddress(port));  
    }  

 Server启动过程：

一.ServerBootstrap配置，NioServerSocketChannelFactory初始化

         1. 构造NioWorkerPool，启动worker线程，默认个数CPU*2

 

Java代码 

       public NioServerSocketChannelFactory(  
        Executor bossExecutor, Executor workerExecutor,  
        int workerCount) {  
    this(bossExecutor, new NioWorkerPool(workerExecutor, workerCount));  
}  

         2.创建worker数组

Java代码 

  workers = new AbstractNioWorker[workerCount];  
  
for (int i = 0; i < workers.length; i++) {  
    workers[i] = createWorker(workerExecutor);  
}  
this.workerExecutor = workerExecutor; 

Java代码 

  protected NioWorker createWorker(Executor executor) {  
    return new NioWorker(executor);  
}  

        3.打开选择器

Java代码 

AbstractNioWorker(Executor executor) {  
this.executor = executor;  
openSelector();  

       4. 启动worker线程

Java代码 

selector = Selector.open();  
....  
          DeadLockProofWorker.start(executor, new ThreadRenamingRunnable(this, "New I/O  worker #" + id));  
...  

      5.初始化NioServerSocketPipelineSink，将workerPool注册到PipelineSink中

sink = new NioServerSocketPipelineSink(workerPool);  

二. bind过程

1.构造叫binder的upstreamHandler，用来捕获bind事件

Java代码 

ChannelHandler binder = new Binder(localAddress, futureQueue);  

  2.构造一个默认的ChannelPipeline作为主的ChannelPipeline

Java代码 

ChannelPipeline bossPipeline = pipeline();  

  3.将binder注册上pipeline

Java代码 

bossPipeline.addLast("binder", binder);  

  4.使用之前构造的NioServerSocketChannelFactory创建主Channel

 

Java代码 

 

1. Channel channel = getFactory().newChannel(bossPipeline);  

 

a.在父类AbstractChannel中关联pipeline和channel

 

Java代码 

 

1. pipeline.attach(this, sink);  

  b.打开一个ServerSocketChannel

 

Java代码 

 

1. socket = ServerSocketChannel.open();  

  c.使用非阻塞模式

 

Java代码 

 

1. socket.configureBlocking(false);  

 

 

d.触发channelOpen事件

 

Java代码 

 

1. fireChannelOpen(this);  

 

 

e.在父channle中的pipeline链中执行，这里只有一个handler就是之前的binder

 

Java代码 

 

1. channel.getPipeline().sendUpstream(  
2.                 new UpstreamChannelStateEvent(  
3.                         channel, ChannelState.OPEN, Boolean.TRUE));  

 

f.binder处理channelOpen事件

1.将之前在ServerBootstrap中注册的ChannelFactory和主Channel关联

 

Java代码 

 

1. evt.getChannel().getConfig().setPipelineFactory(getPipelineFactory());  

 

2.按parent和child对设置的参数进行归类，将parent的参数和主channel关联

 

Java代码 

 

1. evt.getChannel().getConfig().setOptions(parentOptions);  

 

3.对之前打开的ServerSocketChannel执行bind

 

Java代码 

 

1. evt.getChannel().bind(localAddress)  

 

4.在工具类Channels中执行bind，其实是发送一个bind的downStream事件

 

Java代码 

 

1. channel.getPipeline().sendDownstream(new DownstreamChannelStateEvent(  
2.                 channel, future, ChannelState.BOUND, localAddress));  

 

5.由于主channel的pipeline只有一个binder的upstreamHandler，所以这个bind事件直接就到Pipeline最下面的Sink中处理了，这里是NioServerSocketPipelineSink

6.NioServerSocketPipelineSink处理bind事件

 

Java代码 

public void eventSunk(  
                    ChannelPipeline pipeline, ChannelEvent e) throws Exception {  
            Channel channel = e.getChannel();  
            if (channel instanceof NioServerSocketChannel) {  
                    handleServerSocket(e);  
            } else if (channel instanceof NioSocketChannel) {  
                    handleAcceptedSocket(e);  
        }  
        }  

7.这里起的是服务端，所以channel是一个NioServerSocketChannel

8.处理BOUND事件

 

Java代码 

case BOUND:  
            if (value != null) {  
                bind(channel, future, (SocketAddress) value);  
            } else {  
                close(channel, future);  
            }  
            break;  

9.拿到channel的socket执行bind

 

Java代码 

 

1. channel.socket.socket().bind(localAddress, channel.getConfig().getBacklog());  

 

10.bind成功后，触发BOUND事件

 

Java代码 

 

1. channel.getPipeline().sendUpstream(  
2.                 new UpstreamChannelStateEvent(  
3.                         channel, ChannelState.BOUND, localAddress));  

 

11.binder处理BOUND这个upstream事件，这里bind没有处理，因为没有扩展接口

12.启动BOSS线程，用来接受新的请求

 

Java代码 

 

Executor bossExecutor =  
                ((NioServerSocketChannelFactory) channel.getFactory()).bossExecutor;  
            DeadLockProofWorker.start(bossExecutor,  
                    new ThreadRenamingRunnable(new Boss(channel),  
                            "New I/O server boss #" + id + " (" + channel + ')'));  

13.Boss构造中，创建一个selector，并将之前已经bind的channel注册上去，注册的key是accept

 

Java代码 

 

1. selector = Selector.open();  
2.     ...  
3.                 channel.socket.register(selector, SelectionKey.OP_ACCEPT);  

 

g.由于主channel的pipeline只有一个handler，所以事件处理在binder这里结束了

h.向阻塞队列发成功信号

 

Java代码 

 

1. boolean finished = futureQueue.offer(evt.getChannel().bind(localAddress));  

 

5.主线程从阻塞队列中获取信号，如果bind不成功，则抛出异常

 

Java代码 

 

1. future = futureQueue.poll(Integer.MAX_VALUE, TimeUnit.SECONDS);  

 

6.bind结束，server启动成功，此时Boss和worker线程都已成功启动，可以对外服务了。