4.3 dubbo provider启动之终极之战 netty启动详解

启动过程中的‘阻碍’讲完了，该进入正题了。

这里启动选择的默认dubbo协议的netty4。从看源码的角度要剔除掉很多的干扰项，dubbo为了兼容，所以扩展了很多东西，其中有大部分可能是不会使用使用，在研究的dubbo的时候一定要选择重点逻辑研究，比如像一些配置怎么在这里，这个配置从哪里来，到哪里去，可以暂缓研究，也可以不去研究，到亲手操刀写的时候，再研究配置和数据传递为何要这样写不迟，这样能以最简短的时间深入了解整个架构。像netty的组件层，各个server的实现都是实现的abstract里面的doOpen，但是有netty3，甚至mina的实现，在目前的角度，没多大的意义。毕竟netty4稳定许多年了。适时的放弃一些源码中间的逻辑和自身的逻辑校验之内的，只看你需要的才是王道，你去菜市场买个猪蹄，总不至于要从杀猪开始一步一步看起吧？哈哈，下面进入provider的最终启动。

先总的说一下大纲：dubbo以url传递信息，要发布的接口封装成invoker缓存供给调用。然后辅以filter，SPI，wrapper等构造出dubbo整个服务器的稳定性和兼容性。

1.service.export()进入netty启动。

        ServiceConfig service = new ServiceConfig<>();
        service.setApplication(application);
        // 使用指定的协议暴露服务
        service.setProtocol(protocol);
        // 向指定注册中心注册，在多个注册中心时使用
        service.setRegistry(registry);
        // 服务接口名
        service.setInterface(DemoService.class);
        // 服务对象实现引用
        service.setRef(new DemoServiceImpl());
        // 发布接口
        service.export();

2.doExport()继续进入发布。

    public synchronized void export() {
        checkAndUpdateSubConfigs();

        if (!shouldExport()) {
            return;
        }

        if (shouldDelay()) {
            delayExportExecutor.schedule(this::doExport, delay, TimeUnit.MILLISECONDS);
        } else {
            doExport();
        }
    }

3.doExportUrls继续进入发布。

    // 发布
    protected synchronized void doExport() {
        if (unexported) {
            throw new IllegalStateException("The service " + interfaceClass.getName() + " has already unexported!");
        }
        if (exported) {
            return;
        }
        exported = true;

        if (StringUtils.isEmpty(path)) {
            path = interfaceName;
        }
        doExportUrls();
    }

4.1 doExportUrlsFor1Protocol继续进入发布。

private void doExportUrls() {
    List registryURLs = loadRegistries(true);
    for (ProtocolConfig protocolConfig : protocols) {
        String pathKey = URL.buildKey(getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), group, version);
        ProviderModel providerModel = new ProviderModel(pathKey, ref, interfaceClass);
        ApplicationModel.initProviderModel(pathKey, providerModel);
        doExportUrlsFor1Protocol(protocolConfig, registryURLs);
    }
}

4.2 初始化ProviderModel

/**
* ProviderModel which is about published services
*/
public class ProviderModel {
    // pathKey==>1.0/org.apache.dubbo.demo.DemoService:1.0
    private final String serviceName;
    // 接口实现类
    private final Object serviceInstance;
        // 接口
    private final Class serviceInterfaceClass;
   // 接口包含的方法
    private final Map> methods = new HashMap>();
    。。。。。。
}

4.3  调用ProviderModel的构造函数里面的initMethod()

// 初始化接口方法
private void initMethod() {
    Method[] methodsToExport = null;
    methodsToExport = this.serviceInterfaceClass.getMethods();
    for (Method method : methodsToExport) {
        method.setAccessible(true);
        List methodModels = methods.get(method.getName());
        if (methodModels == null) {
            methodModels = new ArrayList(1);
            methods.put(method.getName(), methodModels);
        }
        methodModels.add(new ProviderMethodModel(method, serviceName));
    }
}

4.4 将抽象出来的ProviderModel放进ApplicationModel中的providedServices，进行缓存

public static void initProviderModel(String serviceName, ProviderModel providerModel) {
    if (providedServices.putIfAbsent(serviceName, providerModel) != null) {
        LOGGER.warn("Already register the same:" + serviceName);
    }
}

5 进入doExportUrlsFor1Protocol（）

   private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List registryURLs) {{
        String name = protocolConfig.getName();// 获取协议名称
        if (StringUtils.isEmpty(name)) {
            name = Constants.DUBBO;
        }

        Map map = new HashMap();// 初始化一系列参数
        map.put(Constants.SIDE_KEY, Constants.PROVIDER_SIDE);
        appendRuntimeParameters(map);
        appendParameters(map, application);
        appendParameters(map, module);
        appendParameters(map, provider, Constants.DEFAULT_KEY);
        appendParameters(map, protocolConfig);
        appendParameters(map, this);
        
        ......
        ......
        ......


        // export service 导出服务
        // 获得ip
        String host = this.findConfigedHosts(protocolConfig, registryURLs, map);
        // 获取端口
        Integer port = this.findConfigedPorts(protocolConfig, name, map);
        URL url = new URL(name, host, port, getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), map);

        if (ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
                .hasExtension(url.getProtocol())) {
            url = ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
                    .getExtension(url.getProtocol()).getConfigurator(url).configure(url);
        }

        String scope = url.getParameter(Constants.SCOPE_KEY);
        // don't export when none is configured
        if (!Constants.SCOPE_NONE.equalsIgnoreCase(scope)) {

            // export to local if the config is not remote (export to remote only when config is remote)
            if (!Constants.SCOPE_REMOTE.equalsIgnoreCase(scope)) {
                exportLocal(url);
            }
            // export to remote if the config is not local (export to local only when config is local)
            if (!Constants.SCOPE_LOCAL.equalsIgnoreCase(scope)) {
                if (logger.isInfoEnabled()) {
                    logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url);
                }
                if (CollectionUtils.isNotEmpty(registryURLs)) {
                    for (URL registryURL : registryURLs) {
                        url = url.addParameterIfAbsent(Constants.DYNAMIC_KEY, registryURL.getParameter(Constants.DYNAMIC_KEY));
                        URL monitorUrl = loadMonitor(registryURL);
                        if (monitorUrl != null) {
                            url = url.addParameterAndEncoded(Constants.MONITOR_KEY, monitorUrl.toFullString());
                        }
                        if (logger.isInfoEnabled()) {
                            logger.info("Register dubbo service " + interfaceClass.getName() + " url " + url + " to registry " + registryURL);
                        }

                        // For providers, this is used to enable custom proxy to generate invoker
                        String proxy = url.getParameter(Constants.PROXY_KEY);
                        if (StringUtils.isNotEmpty(proxy)) {
                            registryURL = registryURL.addParameter(Constants.PROXY_KEY, proxy);
                        }
                        // 生成Invoker
                        Invoker invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString()));
                        // Invoker包装类，包含了serviceConfig参数
                        DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
                        // 发布Invoker
                        Exporter exporter = protocol.export(wrapperInvoker);
                        exporters.add(exporter);
                    }
                } else {
                    Invoker invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, url);
                    DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
                    
                    Exporter exporter = protocol.export(wrapperInvoker);
                    exporters.add(exporter);
                }
                /**
                 * @since 2.7.0
                 * ServiceData Store
                 */
                MetadataReportService metadataReportService = null;
                if ((metadataReportService = getMetadataReportService()) != null) {
                    metadataReportService.publishProvider(url);
                }
            }
        }
        this.urls.add(url);
    }

6.进入QosProtocolWrapper,启动qos服务。

    @Override
    public  Exporter export(Invoker invoker) throws RpcException {
        if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
            startQosServer(invoker.getUrl());// qos:Quality of Service,动态的对服务进行查询和控制
            return protocol.export(invoker);
        }
        return protocol.export(invoker);
    }

7.最终发布是在RegistryProtocol里面。

   @Override
    public  Exporter export(final Invoker originInvoker) throws RpcException {
        URL registryUrl = getRegistryUrl(originInvoker);
        // url to export locally
        URL providerUrl = getProviderUrl(originInvoker);

        // Subscribe the override data
        // FIXME When the provider subscribes, it will affect the scene : a certain JVM exposes the service and call
        //  the same service. Because the subscribed is cached key with the name of the service, it causes the
        //  subscription information to cover.
        final URL overrideSubscribeUrl = getSubscribedOverrideUrl(providerUrl);
        final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
        overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);

        providerUrl = overrideUrlWithConfig(providerUrl, overrideSubscribeListener);
        // 发布Invoker！！！！！！！！！！！！！！！！！！！
        final ExporterChangeableWrapper exporter = doLocalExport(originInvoker, providerUrl);

        // url to registry
        final Registry registry = getRegistry(originInvoker);
        final URL registeredProviderUrl = getRegisteredProviderUrl(providerUrl, registryUrl);
        ProviderInvokerWrapper providerInvokerWrapper = ProviderConsumerRegTable.registerProvider(originInvoker,
                registryUrl, registeredProviderUrl);
        //to judge if we need to delay publish
        boolean register = registeredProviderUrl.getParameter("register", true);
        if (register) {
            register(registryUrl, registeredProviderUrl);
            providerInvokerWrapper.setReg(true);
        }

        // Deprecated! Subscribe to override rules in 2.6.x or before.
        registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);

        exporter.setRegisterUrl(registeredProviderUrl);
        exporter.setSubscribeUrl(overrideSubscribeUrl);
        //Ensure that a new exporter instance is returned every time export
        return new DestroyableExporter<>(exporter);
    }

8.接着进入RegistryProtocol的doLocalExport方法。

    private  ExporterChangeableWrapper doLocalExport(final Invoker originInvoker, URL providerUrl) {
        // key:dubbo://192.168.55.168:20880/org.apache.dubbo.demo.DemoService?accepts=0&anyhost=true&application=dubbo-demo-api-provider&bind.ip=192.168.55.168&bind.port=20880&compiler=javassist&default.deprecated=false&default.dynamic=false&default.register=true&deprecated=false&dispatcher=direct&dubbo=2.0.2&generic=false&interface=org.apache.dubbo.demo.DemoService&methods=sayHello&pid=13028®ister=true&release=&side=provider&threadpool=fixed&threads=200×tamp=1556159946813
        String key = getCacheKey(originInvoker);

        return (ExporterChangeableWrapper) bounds.computeIfAbsent(key, s -> {
            Invoker invokerDelegate = new InvokerDelegate<>(originInvoker, providerUrl);
            return new ExporterChangeableWrapper<>((Exporter) protocol.export(invokerDelegate), originInvoker);
        });
    }

9.再次回到ProtocolFilterWrapper中。这里很关键，buildInvokerChain这步就是构建dubbo filter，参考前面讲的filter那一章。

    @Override
    public  Exporter export(Invoker invoker) throws RpcException {
        if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
            return protocol.export(invoker);
        }
        // 执行这步
        return protocol.export(buildInvokerChain(invoker, Constants.SERVICE_FILTER_KEY, Constants.PROVIDER));
    }

10.进入QosProtocolWrapper。

    @Override
    public  Exporter export(Invoker invoker) throws RpcException {
        if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
            startQosServer(invoker.getUrl());// qos:Quality of Service,动态的对服务进行查询和控制
            return protocol.export(invoker);
        }
        return protocol.export(invoker);
    }

11.进入ProtocolListenerWrapper执行。

    @Override
    public  Exporter export(Invoker invoker) throws RpcException {
        if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
            return protocol.export(invoker);
        }
        return new ListenerExporterWrapper(protocol.export(invoker),
                Collections.unmodifiableList(ExtensionLoader.getExtensionLoader(ExporterListener.class)
                        .getActivateExtension(invoker.getUrl(), Constants.EXPORTER_LISTENER_KEY)));
    }

12.最终回到dubboProtocol，启动netty服务器。

@Override
public  Exporter export(Invoker invoker) throws RpcException {
    URL url = invoker.getUrl();

    // key-->org.apache.dubbo.demo.DemoService:20880
    String key = serviceKey(url);
    DubboExporter exporter = new DubboExporter(invoker, key, exporterMap);
    exporterMap.put(key, exporter);

    //export an stub service for dispatching event
    Boolean isStubSupportEvent = url.getParameter(Constants.STUB_EVENT_KEY, Constants.DEFAULT_STUB_EVENT);
    Boolean isCallbackservice = url.getParameter(Constants.IS_CALLBACK_SERVICE, false);
    if (isStubSupportEvent && !isCallbackservice) {
        String stubServiceMethods = url.getParameter(Constants.STUB_EVENT_METHODS_KEY);
        if (stubServiceMethods == null || stubServiceMethods.length() == 0) {
            if (logger.isWarnEnabled()) {
                logger.warn(new IllegalStateException("consumer [" + url.getParameter(Constants.INTERFACE_KEY) +
                        "], has set stubproxy support event ,but no stub methods founded."));
            }

        } else {
            stubServiceMethodsMap.put(url.getServiceKey(), stubServiceMethods);
        }
    }
    // 启动netty服务器！！！！！！！！！！！！！！！！！
    openServer(url);
    optimizeSerialization(url);

    return exporter;
}

13.进入openServer。

    private void openServer(URL url) {
        // find server. key==>192.168.55.168:20880
        String key = url.getAddress();
        //client can export a service which's only for server to invoke
        boolean isServer = url.getParameter(Constants.IS_SERVER_KEY, true);
        if (isServer) {
            ExchangeServer server = serverMap.get(key);
            if (server == null) {
                synchronized (this) {
                    server = serverMap.get(key);
                    if (server == null) {
                        // 构建netty server
                        serverMap.put(key, createServer(url));
                    }
                }
            } else {
                // server supports reset, use together with override
                server.reset(url);
            }
        }
    }

14.进入createServer。

    private ExchangeServer createServer(URL url) {
        url = URLBuilder.from(url)
                // send readonly event when server closes, it's enabled by default
                .addParameterIfAbsent(Constants.CHANNEL_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString())
                // enable heartbeat by default
                .addParameterIfAbsent(Constants.HEARTBEAT_KEY, String.valueOf(Constants.DEFAULT_HEARTBEAT))
                .addParameter(Constants.CODEC_KEY, DubboCodec.NAME)
                .build();
        String str = url.getParameter(Constants.SERVER_KEY, Constants.DEFAULT_REMOTING_SERVER);

        if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) {
            throw new RpcException("Unsupported server type: " + str + ", url: " + url);
        }

        ExchangeServer server;
        try {
            // 绑定ip端口启动服务器
            server = Exchangers.bind(url, requestHandler);
        } catch (RemotingException e) {
            throw new RpcException("Fail to start server(url: " + url + ") " + e.getMessage(), e);
        }

        str = url.getParameter(Constants.CLIENT_KEY);
        if (str != null && str.length() > 0) {
            Set supportedTypes = ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions();
            if (!supportedTypes.contains(str)) {
                throw new RpcException("Unsupported client type: " + str);
            }
        }

        return server;
    }

15.进入Exchanges。

    public static ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException {
        if (url == null) {
            throw new IllegalArgumentException("url == null");
        }
        if (handler == null) {
            throw new IllegalArgumentException("handler == null");
        }
        url = url.addParameterIfAbsent(Constants.CODEC_KEY, "exchange");
        // bind端口
        return getExchanger(url).bind(url, handler);
    }

16.最终进入NettyTransporter。

    @Override
    public Server bind(URL url, ChannelHandler listener) throws RemotingException {
        return new NettyServer(url, listener);
    }

17.调用super（）进入AbstractServer。

    public AbstractServer(URL url, ChannelHandler handler) throws RemotingException {
        super(url, handler);
        localAddress = getUrl().toInetSocketAddress();
        // ip
        String bindIp = getUrl().getParameter(Constants.BIND_IP_KEY, getUrl().getHost());
        // 端口
        int bindPort = getUrl().getParameter(Constants.BIND_PORT_KEY, getUrl().getPort());
        if (url.getParameter(Constants.ANYHOST_KEY, false) || NetUtils.isInvalidLocalHost(bindIp)) {
            bindIp = Constants.ANYHOST_VALUE;
        }
        bindAddress = new InetSocketAddress(bindIp, bindPort);
        this.accepts = url.getParameter(Constants.ACCEPTS_KEY, Constants.DEFAULT_ACCEPTS);
        this.idleTimeout = url.getParameter(Constants.IDLE_TIMEOUT_KEY, Constants.DEFAULT_IDLE_TIMEOUT);
        try {
            // 启动netty服务器
            doOpen();
            if (logger.isInfoEnabled()) {
                logger.info("Start " + getClass().getSimpleName() + " bind " + getBindAddress() + ", export " + getLocalAddress());
            }
        } catch (Throwable t) {
            throw new RemotingException(url.toInetSocketAddress(), null, "Failed to bind " + getClass().getSimpleName()
                    + " on " + getLocalAddress() + ", cause: " + t.getMessage(), t);
        }
        //fixme replace this with better method
        DataStore dataStore = ExtensionLoader.getExtensionLoader(DataStore.class).getDefaultExtension();
        executor = (ExecutorService) dataStore.get(Constants.EXECUTOR_SERVICE_COMPONENT_KEY, Integer.toString(url.getPort()));
    }

18.执行NettyServer重写的doOpen方法。到这一步整个netty启动过程就结束了。

    @Override
    protected void doOpen() throws Throwable {
        bootstrap = new ServerBootstrap();

        bossGroup = new NioEventLoopGroup(1, new DefaultThreadFactory("NettyServerBoss", true));
        workerGroup = new NioEventLoopGroup(getUrl().getPositiveParameter(Constants.IO_THREADS_KEY, Constants.DEFAULT_IO_THREADS),
                new DefaultThreadFactory("NettyServerWorker", true));

        final NettyServerHandler nettyServerHandler = new NettyServerHandler(getUrl(), this);
        channels = nettyServerHandler.getChannels();

        bootstrap.group(bossGroup, workerGroup)
                .channel(NioServerSocketChannel.class)
                .childOption(ChannelOption.TCP_NODELAY, Boolean.TRUE)
                .childOption(ChannelOption.SO_REUSEADDR, Boolean.TRUE)
                .childOption(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT)
                .childHandler(new ChannelInitializer() {
                    @Override
                    protected void initChannel(NioSocketChannel ch) throws Exception {
                        // FIXME: should we use getTimeout()?
                        int idleTimeout = UrlUtils.getIdleTimeout(getUrl());
                        NettyCodecAdapter adapter = new NettyCodecAdapter(getCodec(), getUrl(), NettyServer.this);
                        ch.pipeline()//.addLast("logging",new LoggingHandler(LogLevel.INFO))//for debug
                                .addLast("decoder", adapter.getDecoder())
                                .addLast("encoder", adapter.getEncoder())
                                .addLast("server-idle-handler", new IdleStateHandler(0, 0, idleTimeout, MILLISECONDS))
                                .addLast("handler", nettyServerHandler);
                    }
                });
        // bind
        ChannelFuture channelFuture = bootstrap.bind(getBindAddress());
        channelFuture.syncUninterruptibly();
        channel = channelFuture.channel();

    }