启动过程总体流程

Server > ThreadPool 、Handler > Connector

Server

启动过程，主要做了以下的事情:

• 检查，如果 ErrorHandler 没有，则创建一个

• 注册和启动关闭钩子

• 启动除了 Connector 的其他所有组件 ThreadPool 、Handler

• 最后启动 Connector

  // Server.java @Override protected void doStart() throws Exception { // 1.如果 ErrorHandler 没有，则创建一个 if (_errorHandler == null) _errorHandler = getBean(ErrorHandler.class); if (_errorHandler == null) setErrorHandler(new ErrorHandler()); if (_errorHandler instanceof ErrorHandler.ErrorPageMapper) LOG.warn("ErrorPageMapper not supported for Server level Error Handling"); _errorHandler.setServer(this); //2.If the Server should be stopped when the jvm exits, register //with the shutdown handler thread. if (getStopAtShutdown()) ShutdownThread.register(this); //3. Register the Server with the handler thread for receiving //remote stop commands ShutdownMonitor.register(this); //Start a thread waiting to receive "stop" commands. ShutdownMonitor.getInstance().start(); // initialize // 4.启动 Server, 将会启动除了 Connector 的其他所有组件 MultiException mex = new MultiException(); try { super.doStart(); } catch (Throwable e) { mex.add(e); } // 5.最后启动 Connector if (mex.size() == 0) { for (Connector connector : _connectors) { try { connector.start(); } catch (Throwable e) { mex.add(e); } } } if (isDumpAfterStart()) dumpStdErr(); mex.ifExceptionThrow(); LOG.info(String.format("Started @%dms", Uptime.getUptime())); }

比如 embedded-jetty-jsp

         server = new Server();

        // Define ServerConnector
        ServerConnector connector = new ServerConnector(server);
        connector.setPort(port);
        server.addConnector(connector);

         // Create Servlet context
        ServletContextHandler servletContextHandler = new ServletContextHandler(ServletContextHandler.SESSIONS);
        servletContextHandler.setContextPath("/");
        servletContextHandler.setResourceBase(baseUri.toASCIIString());

        // Since this is a ServletContextHandler we must manually configure JSP support.
        enableEmbeddedJspSupport(servletContextHandler);
    
        // Add Application Servlets
        servletContextHandler.addServlet(DateServlet.class, "/date/");
        // Create Example of mapping jsp to path spec
        ServletHolder holderAltMapping = new ServletHolder();
        holderAltMapping.setName("foo.jsp");
        holderAltMapping.setForcedPath("/test/foo/foo.jsp");
        servletContextHandler.addServlet(holderAltMapping, "/test/foo/");
    
        // Default Servlet (always last, always named "default")
        ServletHolder holderDefault = new ServletHolder("default", DefaultServlet.class);
        holderDefault.setInitParameter("resourceBase", baseUri.toASCIIString());
        holderDefault.setInitParameter("dirAllowed", "true");
        servletContextHandler.addServlet(holderDefault, "/");
        server.setHandler(servletContextHandler);

        // Start Server
        server.start();

Connector

Connector 的实现类 ServerConnector 中，有一个_acceptors的数组，在 Connector 启动的时候, 会根据_acceptors数组的长度创建对应数量的 Acceptor，而 Acceptor 的个数可以配置。

• 启动 HttpConnectionFactory, SelectorManager 等

• 根据_acceptors数组的长度创建对应数量的 Acceptor， 并启动

  // AbstractConnector.java @Override protected void doStart() throws Exception { ... // 启动 HttpConnectionFactory, SelectorManager 等 super.doStart(); ... for (int i = 0; i < _acceptors.length; i++) { Acceptor a = new Acceptor(i); addBean(a); getExecutor().execute(a); } }

Acceptor 本质是一个线程。

// ServerConnector.java
    @Override
    public void accept(int acceptorID) throws IOException
    {
        ServerSocketChannel serverChannel = _acceptChannel;
        if (serverChannel != null && serverChannel.isOpen())
        {
            // 阻塞等待客户端的连接
            SocketChannel channel = serverChannel.accept();
            // 连接成功
            accepted(channel);
        }
    }
     
    // 这里已经连接成功
    private void accepted(SocketChannel channel) throws IOException
    {
        channel.configureBlocking(false);
        Socket socket = channel.socket();
        configure(socket);
        // _manager 是 SelectorManager 实例，里面管理了所有的 Selector 实例
        _manager.accept(channel);
    }

SelectorManager

SelectorManager 启动的时候，会把所有的 ManagedSelector 启动了。

// SelectorManager.java
    @Override
    protected void doStart() throws Exception
    {
        _lease = ThreadPoolBudget.leaseFrom(getExecutor(), this, _selectors.length);
        for (int i = 0; i < _selectors.length; i++)
        {
            ManagedSelector selector = newSelector(i);
            _selectors[i] = selector;
            addBean(selector);
        }
        super.doStart();
    }

ManagedSelector 启动的时候，会启动 SelectorProducer （使用策略 EatWhatYouKill ）

// ManagedSelector.java
    public ManagedSelector(SelectorManager selectorManager, int id)
    {
        _selectorManager = selectorManager;
        _id = id;
        SelectorProducer producer = new SelectorProducer();
        Executor executor = selectorManager.getExecutor();
        _strategy = new EatWhatYouKill(producer, executor);
        addBean(_strategy, true);
        setStopTimeout(5000);
    }
    
    @Override
    protected void doStart() throws Exception
    {
        super.doStart();
        _selector = _selectorManager.newSelector();

        // The producer used by the strategies will never
        // be idle (either produces a task or blocks).

        // The normal strategy obtains the produced task, schedules
        // a new thread to produce more, runs the task and then exits.
        _selectorManager.execute(_strategy::produce);

        // Set started only if we really are started
        Start start = new Start();
        submit(start);
        start._started.await();
    }

相关

Jetty源码导读二：接受请求过程 https://my.oschina.net/langxSpirit/blog/3144657

by 斯武丶风晴 https://my.oschina.net/langxSpirit