tomcat8.5.57源码阅读笔记4.2

StandardService#startInternal中, 除了调用了 engine.start()外, 还调用了 connector#start()

Connector#start()

 connector.start()最终调用的是 Connector#startInternal()方法.

protected void startInternal() throws LifecycleException {

    // Validate settings before starting
    if (getPort() < 0) {
        throw new LifecycleException(sm.getString(
                "coyoteConnector.invalidPort", Integer.valueOf(getPort())));
    }

    setState(LifecycleState.STARTING);

    try {
        //Http11NioProtocol#start() -> AbstractProtocol#start()
        protocolHandler.start();
    } catch (Exception e) {
        throw new LifecycleException(
                sm.getString("coyoteConnector.protocolHandlerStartFailed"), e);
    }
}

这里的 protocolHandler 就是 Http11NioProtocol

 这里start调用的是 org.apache.coyote.AbstractProtocol#start

public void start() throws Exception {
    if (getLog().isInfoEnabled()) {
        getLog().info(sm.getString("abstractProtocolHandler.start", getName()));
    }

    //NioEndpoint#startInternal()
    endpoint.start();

    // Start timeout thread
    asyncTimeout = new AsyncTimeout();
    Thread timeoutThread = new Thread(asyncTimeout, getNameInternal() + "-AsyncTimeout");
    int priority = endpoint.getThreadPriority();
    if (priority < Thread.MIN_PRIORITY || priority > Thread.MAX_PRIORITY) {
        priority = Thread.NORM_PRIORITY;
    }
    timeoutThread.setPriority(priority);
    timeoutThread.setDaemon(true);
    timeoutThread.start();
}

endpoint 是 NipEndpoint, 他是与 Http11NioProtocol 对应的, 实在创建 Http11NioProtocol  的时候, 就写死传进来的.

这里的start最终也是调用 org.apache.tomcat.util.net.NioEndpoint#startInternal

public void startInternal() throws Exception {

    if (!running) {
        running = true;
        paused = false;

        processorCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
                socketProperties.getProcessorCache());
        eventCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
                        socketProperties.getEventCache());
        nioChannels = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
                socketProperties.getBufferPool());

        // Create worker collection
        if ( getExecutor() == null ) {
            createExecutor();
        }

        initializeConnectionLatch();

        // Start poller threads
        pollers = new Poller[getPollerThreadCount()];
        for (int i=0; i<pollers.length; i++) {
            pollers[i] = new Poller();
            Thread pollerThread = new Thread(pollers[i], getName() + "-ClientPoller-"+i);
            pollerThread.setPriority(threadPriority);
            pollerThread.setDaemon(true);
　　　　　　  //启动 poller 线程
            pollerThread.start();
        }

        startAcceptorThreads();
    }
}

1. 多线程的方式, 启动了 poller 线程

2. 调用 startAcceptorThreads 方法, 启动了接收线程

protected final void startAcceptorThreads() {
    int count = getAcceptorThreadCount();
    acceptors = new Acceptor[count];

    for (int i = 0; i < count; i++) {
        acceptors[i] = createAcceptor();
        String threadName = getName() + "-Acceptor-" + i;
        acceptors[i].setThreadName(threadName);
        Thread t = new Thread(acceptors[i], threadName);
        t.setPriority(getAcceptorThreadPriority());
        t.setDaemon(getDaemon());
        t.start();
    }
}

Poller

//org.apache.tomcat.util.net.NioEndpoint.Poller#run
@Override
public void run() {
    // Loop until destroy() is called
    while (true) {

        boolean hasEvents = false;

        try {
            if (!close) {
                hasEvents = events();
                if (wakeupCounter.getAndSet(-1) > 0) {
                    //if we are here, means we have other stuff to do
                    //do a non blocking select
                    keyCount = selector.selectNow();
                } else {
                    keyCount = selector.select(selectorTimeout);
                }
                wakeupCounter.set(0);
            }
            if (close) {
                //获取了 EventQueue 中所有的 PollerEvent, 然后依次调用 PollerEvent#run() 方法.
                //将 socket 注册到 selector 中.
                events();
                timeout(0, false);
                try {
                    selector.close();
                } catch (IOException ioe) {
                    log.error(sm.getString("endpoint.nio.selectorCloseFail"), ioe);
                }
                break;
            }
        } catch (Throwable x) {
            ExceptionUtils.handleThrowable(x);
            log.error("",x);
            continue;
        }
        //either we timed out or we woke up, process events first
        if ( keyCount == 0 ) hasEvents = (hasEvents | events());

        Iterator<SelectionKey> iterator =
            keyCount > 0 ? selector.selectedKeys().iterator() : null;
        // Walk through the collection of ready keys and dispatch
        // any active event.
        while (iterator != null && iterator.hasNext()) {
            SelectionKey sk = iterator.next();
            NioSocketWrapper attachment = (NioSocketWrapper)sk.attachment();
            // Attachment may be null if another thread has called
            // cancelledKey()
            if (attachment == null) {
                iterator.remove();
            } else {
                iterator.remove();
                //处理 OPEN_READ 和 OPEN_WRITE 事件
                processKey(sk, attachment);
            }
        }//while

        //process timeouts
        timeout(keyCount,hasEvents);
    }//while

    getStopLatch().countDown();
}

while(true) , 设置死循环, 在没有请求进来的时候, 不会执行什么我想看到的功能, 也相当于是在等待客户端请求进来

Acceptor

protected class Acceptor extends AbstractEndpoint.Acceptor {
    @Override
    public void run() {
        int errorDelay = 0;
        // Loop until we receive a shutdown command
        while (running) {
            // Loop if endpoint is paused
            while (paused && running) {
                state = AcceptorState.PAUSED;
                try {
                    Thread.sleep(50);
                } catch (InterruptedException e) {
                    // Ignore
                }
            }

            if (!running) {
                break;
            }
            state = AcceptorState.RUNNING;

            try {
                //if we have reached max connections, wait
                //最大连接数量的限制
                countUpOrAwaitConnection();

                SocketChannel socket = null;
                try {
                    // Accept the next incoming connection from the server
                    // socket 监听阻塞
                    socket = serverSock.accept();
                    //调试添加 监听到之后, 继续往下执行
                    System.out.println("调试添加 : " + socket);
                }
                catch (IOException ioe) {
                    // We didn't get a socket
                    countDownConnection();
                    if (running) {
                        // Introduce delay if necessary
                        errorDelay = handleExceptionWithDelay(errorDelay);
                        // re-throw
                        throw ioe;
                    } else {
                        break;
                    }
                }
                // Successful accept, reset the error delay
                errorDelay = 0;

                // Configure the socket
                if (running && !paused) {
                    // setSocketOptions() will hand the socket off to
                    // an appropriate processor if successful
                    // 调用 NioEndpoint#setSocketOptions() 方法, 对socket进行处理
                    if (!setSocketOptions(socket)) {
                        closeSocket(socket);
                    }
                } else {
                    closeSocket(socket);
                }
            } catch (Throwable t) {
                ExceptionUtils.handleThrowable(t);
                log.error(sm.getString("endpoint.accept.fail"), t);
            }
        }
        state = AcceptorState.ENDED;
    }


    private void closeSocket(SocketChannel socket) {
        ......
    }
}

Acceptor会一直阻塞在这里, 监听socket, 等待客户端连接进来