1 NioEventLoop概述

• 总述

  

2 NioEventLoop创建概述

对应

对应 对应 对应

3 ThreadPerTaskThread

2 服务端Channel的创建

bind 对应样例的

看看 channelFactory

• 反射创建服务端 Channel

  

  首先

  
  
  

  创建完毕了
  
  
  

• ANC

  
  
  
  
  
  
  

4 创建NioEventLoop线程

5 创建线程选择器

• 先看看普通的

  
  

• 再看幂2的

  
  

  循环取数组索引下标,& 比取模性能更高

6 NioEventLoop的启动

对应是

对应是

7 NioEventLoop执行概述

8 检测IO事件

对应的源码为

对应的源码为

避免空轮询的再次发生

9 处理IO事件

一句话总结:用数组替换HashSet 的实现,做到 add 时间复杂度为O(1)

private void processSelectedKey(SelectionKey k, AbstractNioChannel ch) {        final AbstractNioChannel.NioUnsafe unsafe = ch.unsafe();        if (!k.isValid()) {            final EventLoop eventLoop;            try {                eventLoop = ch.eventLoop();            } catch (Throwable ignored) {                // If the channel implementation throws an exception because there is no event loop, we ignore this                // because we are only trying to determine if ch is registered to this event loop and thus has authority                // to close ch.                return;            }            // Only close ch if ch is still registerd to this EventLoop. ch could have deregistered from the event loop            // and thus the SelectionKey could be cancelled as part of the deregistration process, but the channel is            // still healthy and should not be closed.            // See https://github.com/netty/netty/issues/5125            if (eventLoop != this || eventLoop == null) {                return;            }            // close the channel if the key is not valid anymore            unsafe.close(unsafe.voidPromise());            return;        }        try {            int readyOps = k.readyOps();            // We first need to call finishConnect() before try to trigger a read(...) or write(...) as otherwise            // the NIO JDK channel implementation may throw a NotYetConnectedException.            if ((readyOps & SelectionKey.OP_CONNECT) != 0) {                // remove OP_CONNECT as otherwise Selector.select(..) will always return without blocking                // See https://github.com/netty/netty/issues/924                int ops = k.interestOps();                ops &= ~SelectionKey.OP_CONNECT;                k.interestOps(ops);                unsafe.finishConnect();            }            // Process OP_WRITE first as we may be able to write some queued buffers and so free memory.            if ((readyOps & SelectionKey.OP_WRITE) != 0) {                // Call forceFlush which will also take care of clear the OP_WRITE once there is nothing left to write                ch.unsafe().forceFlush();            }            // Also check for readOps of 0 to workaround possible JDK bug which may otherwise lead            // to a spin loop            if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {                unsafe.read();                if (!ch.isOpen()) {                    // Connection already closed - no need to handle write.                    return;                }            }        } catch (CancelledKeyException ignored) {            unsafe.close(unsafe.voidPromise());        }    }

Netty 默认通过反射将selector 底层的 HashSet 实现转为数组优化

处理每个 ketSet 时都会取到对应的 attachment,即在向 selector注册 io 事件时绑定的经过 Netty 封装后的 channel

10 -reactor线程任务的执行