Netty源码分析-NioEventLoop(二)

NioEventLoop源码分析。

EventLoop的本质：内部一个线程，一个有序队列存储，线程源源不断的运行队列中的任务。

 

register方法把java-nio的channel注册到selector上面。

    //把JAVA底层Channel注册到selector上
    public void register(final SelectableChannel ch, final int interestOps, final NioTask<?> task) {
        //把ch注册到java底层selector上面，代码省略了一些安全检查
        try {
            ch.register(selector, interestOps, task);
        } catch (Exception e) {
            throw new EventLoopException("failed to register a channel", e);
        }
    }

 

run方法是核心的启动方法，在父类中，创建好线程启动以后会调用run方法，在这里会处理selector的selelct事件和所有的IO事件

 @Override
    protected void run() {
        //这个方法是父类定义的抽象方法，在父类线程创建启动后调用此方法。
        for (;;) {
            try {
                        //如果底层队列存储在任务hasTasks会返回true，那么调用selelctNow返回key的数量，可能为0
                        //如果没有则返回SelectStrategy.SELECT
                switch (selectStrategy.calculateStrategy(selectNowSupplier, hasTasks())) {
                    case SelectStrategy.CONTINUE:
                        continue;
                    case SelectStrategy.SELECT:

                        //查询selector，如果没有任务则会在selector上阻塞一会，否则立即返回
                        select(wakenUp.getAndSet(false));

                        if (wakenUp.get()) {
                            selector.wakeup();
                        }
                        // fall through
                    default:
                }

                cancelledKeys = 0;
                needsToSelectAgain = false;
                //IO时间的比例
                final int ioRatio = this.ioRatio;
                //如果是百分百
                if (ioRatio == 100) {
                    try {
                        //先处理所有key事件
                        processSelectedKeys();
                    } finally {
                        // Ensure we always run tasks.
                        //然后处理所有IO任务
                        runAllTasks();
                    }
                } else {
                    final long ioStartTime = System.nanoTime();
                    try {
                        //先处理所有key事件
                        processSelectedKeys();
                    } finally {
                        // Ensure we always run tasks.
                        //执行一段时间的IO任务
                        final long ioTime = System.nanoTime() - ioStartTime;
                        runAllTasks(ioTime * (100 - ioRatio) / ioRatio);
                    }
                }
            } catch (Throwable t) {
                handleLoopException(t);
            }
            // Always handle shutdown even if the loop processing threw an exception.
            try {
                if (isShuttingDown()) {
                    closeAll();
                    if (confirmShutdown()) {
                        return;
                    }
                }
            } catch (Throwable t) {
                handleLoopException(t);
            }
        }
    }

 

processSelectedKey，处理selector的selelct到的key。

 private void processSelectedKey(SelectionKey k, AbstractNioChannel ch) {
        final AbstractNioChannel.NioUnsafe unsafe = ch.unsafe();
        if (!k.isValid()) { //key无效
            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;
            }
            
            //如果ch当中的el不是当前对象则return
            if (eventLoop != this || eventLoop == null) {
                return;
            }

            unsafe.close(unsafe.voidPromise());
            return;
        }

        try {
            //获取key的事件类型
            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.
            //如果是连接事件
            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);
                //完成连接
                unsafe.finishConnect();
            }

            //如果是write事件，则调用底层代码写入逻辑
            // 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
            //如果是读事件，交给底层逻辑处理
            if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {
                unsafe.read();
            }
        } catch (CancelledKeyException ignored) {
            unsafe.close(unsafe.voidPromise());
        }
    }