dubbo源码分析系列——dubbo-rpc-default模块源码分析

时间 2019-12-05

标签 dubbo 源码分析系列 rpc default 模块栏目 Dubbo 繁體版

原文原文链接

简化类图

从图中能够看出该模块下的类主要是实现了dubbo-rpc-api和dubbo-remoting-api两个模块中定义的一些接口和抽象类。扩展了一种duubo框架自定义的dubbo协议，包括编解码和方法调用处理等。java

DubboProtocol

该类是抽象协议实现类AbstractProtocol的具体的dubbo协议的实现，从该类开始着手分析。api

发布服务方法export的实现

public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
        URL url = invoker.getUrl();
        
        // export service. 经过url得到该服务的key。格式如：{serviceGroup}/{serviceName}:{serviceVersion}:{port}
        String key = serviceKey(url);
        //Dubbo协议实现的服务发布器。
        DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap);
        exporterMap.put(key, exporter);
        
        //export an stub service for dispaching event
        //参数STUB_EVENT_KEY和IS_CALLBACK_SERVICE的含义不太清楚，须要后续深究。
        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);
            }
        }

        //调用打开服务器绑定url的方法，这个地方是核心，须要进入深究。
        openServer(url);
        
        return exporter;
    }

该方法实现了dubbo协议的服务发布，显示构造一个DubboExporter实现类的Exporter，用于返回。最核心的是调用内部方法openServer(url);将该url发布到dubbo服务器上。咱们进入该方法看看。缓存

private void openServer(URL url) {
        // find server.
        String key = url.getAddress();
        //client 也能够暴露一个只有server能够调用的服务。
        boolean isServer = url.getParameter(Constants.IS_SERVER_KEY,true);
        if (isServer) {
        	ExchangeServer server = serverMap.get(key);
        	if (server == null) {
        		serverMap.put(key, createServer(url));
        	} else {
        		//server支持reset,配合override功能使用
        		server.reset(url);
        	}
        }
    }

该方法是得到url的地址，经过地址找到对应的server，若已经有相同的地址则无需构造新的server，只须要直接使用，只就起到了缓存server的做用，避免重复构建server。若已经找到了该地址，则会调用server.reset(url)重置一下。url中的参数Constants.IS_SERVER_KEY参数能够禁止发布远程服务，只能本地调用。具体意义不是十分清楚。继续进入方法：createServer(url)服务器

private ExchangeServer createServer(URL url) {
        //默认开启server关闭时发送readonly事件
        url = url.addParameterIfAbsent(Constants.CHANNEL_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString());
        //默认开启heartbeat
        url = url.addParameterIfAbsent(Constants.HEARTBEAT_KEY, String.valueOf(Constants.DEFAULT_HEARTBEAT));
        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);

        url = url.addParameter(Constants.CODEC_KEY, Version.isCompatibleVersion() ? COMPATIBLE_CODEC_NAME : DubboCodec.NAME);
        ExchangeServer server;
        try {
            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<String> supportedTypes = ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions();
            if (!supportedTypes.contains(str)) {
                throw new RpcException("Unsupported client type: " + str);
            }
        }
        return server;
    }

该方法先增长了一些默认的参数，好比heartbeat、server等。检查参数的合法性。最后调用Exchangers.bind(url, requestHandler)将url绑定到requestHandler上得到绑定的服务器，Exchangers是网络通信模块dubbo-remoting-api中定义的，详细的含义，等咱们分析该模块再了解。咱们猜想该方法的含义是绑定url的处理器为requestHandler，并返回服务器。requestHandler就是如何处理接收的请求，这个地方是核心，咱们进入该对象的定义看看。网络

private ExchangeHandler requestHandler = new ExchangeHandlerAdapter() {
        
        public Object reply(ExchangeChannel channel, Object message) throws RemotingException {
            if (message instanceof Invocation) {
                Invocation inv = (Invocation) message;
                Invoker<?> invoker = getInvoker(channel, inv);
                //若是是callback 须要处理高版本调用低版本的问题
                if (Boolean.TRUE.toString().equals(inv.getAttachments().get(IS_CALLBACK_SERVICE_INVOKE))){
                    String methodsStr = invoker.getUrl().getParameters().get("methods");
                    boolean hasMethod = false;
                    if (methodsStr == null || methodsStr.indexOf(",") == -1){
                        hasMethod = inv.getMethodName().equals(methodsStr);
                    } else {
                        String[] methods = methodsStr.split(",");
                        for (String method : methods){
                            if (inv.getMethodName().equals(method)){
                                hasMethod = true;
                                break;
                            }
                        }
                    }
                    if (!hasMethod){
                        logger.warn(new IllegalStateException("The methodName "+inv.getMethodName()+" not found in callback service interface ,invoke will be ignored. please update the api interface. url is:" + invoker.getUrl()) +" ,invocation is :"+inv );
                        return null;
                    }
                }
                RpcContext.getContext().setRemoteAddress(channel.getRemoteAddress());
                return invoker.invoke(inv);
            }
            throw new RemotingException(channel, "Unsupported request: " + message == null ? null : (message.getClass().getName() + ": " + message) + ", channel: consumer: " + channel.getRemoteAddress() + " --> provider: " + channel.getLocalAddress());
        }

        @Override
        public void received(Channel channel, Object message) throws RemotingException {
            if (message instanceof Invocation) {
                reply((ExchangeChannel) channel, message);
            } else {
                super.received(channel, message);
            }
        }

        @Override
        public void connected(Channel channel) throws RemotingException {
            invoke(channel, Constants.ON_CONNECT_KEY);
        }

        @Override
        public void disconnected(Channel channel) throws RemotingException {
            if(logger.isInfoEnabled()){
                logger.info("disconected from "+ channel.getRemoteAddress() + ",url:" + channel.getUrl());
            }
            invoke(channel, Constants.ON_DISCONNECT_KEY);
        }
        
        private void invoke(Channel channel, String methodKey) {
            Invocation invocation = createInvocation(channel, channel.getUrl(), methodKey);
            if (invocation != null) {
                try {
                    received(channel, invocation);
                } catch (Throwable t) {
                    logger.warn("Failed to invoke event method " + invocation.getMethodName() + "(), cause: " + t.getMessage(), t);
                }
            }
        }
        
        private Invocation createInvocation(Channel channel, URL url, String methodKey) {
            String method = url.getParameter(methodKey);
            if (method == null || method.length() == 0) {
                return null;
            }
            RpcInvocation invocation = new RpcInvocation(method, new Class<?>[0], new Object[0]);
            invocation.setAttachment(Constants.PATH_KEY, url.getPath());
            invocation.setAttachment(Constants.GROUP_KEY, url.getParameter(Constants.GROUP_KEY));
            invocation.setAttachment(Constants.INTERFACE_KEY, url.getParameter(Constants.INTERFACE_KEY));
            invocation.setAttachment(Constants.VERSION_KEY, url.getParameter(Constants.VERSION_KEY));
            if (url.getParameter(Constants.STUB_EVENT_KEY, false)){
                invocation.setAttachment(Constants.STUB_EVENT_KEY, Boolean.TRUE.toString());
            }
            return invocation;
        }
    };

该对象是一个匿名类对象，实现了接口ExchangeHandler，应该就是一个远程通信的抽象，是一个通信处理类，处理接收到信息。其中方法reply是响应客户端请求信息，它根据Invocation对象得到invoker，最后再调用invoker.invoke方法执行目标对象的方法，将返回结果发回给客户端。其它的几个事件的方法也作了响应的处理，包括：received、connected和disconnected等事件。框架

引用服务方法refer的实现

public <T> Invoker<T> refer(Class<T> serviceType, URL url) throws RpcException {
        // create rpc invoker.
        DubboInvoker<T> invoker = new DubboInvoker<T>(serviceType, url, getClients(url), invokers);
        invokers.add(invoker);
        return invoker;
    }
    
    private ExchangeClient[] getClients(URL url){
        //是否共享链接
        boolean service_share_connect = false;
        int connections = url.getParameter(Constants.CONNECTIONS_KEY, 0);
        //若是connections不配置，则共享链接，不然每服务每链接
        if (connections == 0){
            service_share_connect = true;
            connections = 1;
        }
        
        ExchangeClient[] clients = new ExchangeClient[connections];
        for (int i = 0; i < clients.length; i++) {
            if (service_share_connect){
                clients[i] = getSharedClient(url);
            } else {
                clients[i] = initClient(url);
            }
        }
        return clients;
    }
    
    /**
     *获取共享链接 
     */
    private ExchangeClient getSharedClient(URL url){
        String key = url.getAddress();
        ReferenceCountExchangeClient client = referenceClientMap.get(key);
        if ( client != null ){
            if ( !client.isClosed()){
                client.incrementAndGetCount();
                return client;
            } else {
//                logger.warn(new IllegalStateException("client is closed,but stay in clientmap .client :"+ client));
                referenceClientMap.remove(key);
            }
        }
        ExchangeClient exchagneclient = initClient(url);
        
        client = new ReferenceCountExchangeClient(exchagneclient, ghostClientMap);
        referenceClientMap.put(key, client);
        ghostClientMap.remove(key);
        return client; 
    }

    /**
     * 建立新链接.
     */
    private ExchangeClient initClient(URL url) {
        
        // client type setting.
        String str = url.getParameter(Constants.CLIENT_KEY, url.getParameter(Constants.SERVER_KEY, Constants.DEFAULT_REMOTING_CLIENT));

        String version = url.getParameter(Constants.DUBBO_VERSION_KEY);
        boolean compatible = (version != null && version.startsWith("1.0."));
        url = url.addParameter(Constants.CODEC_KEY, Version.isCompatibleVersion() && compatible ? COMPATIBLE_CODEC_NAME : DubboCodec.NAME);
        //默认开启heartbeat
        url = url.addParameterIfAbsent(Constants.HEARTBEAT_KEY, String.valueOf(Constants.DEFAULT_HEARTBEAT));
        
        // BIO存在严重性能问题，暂时不容许使用
        if (str != null && str.length() > 0 && ! ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) {
            throw new RpcException("Unsupported client type: " + str + "," +
                    " supported client type is " + StringUtils.join(ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions(), " "));
        }
        
        ExchangeClient client ;
        try {
            //设置链接应该是lazy的 
            if (url.getParameter(Constants.LAZY_CONNECT_KEY, false)){
                client = new LazyConnectExchangeClient(url ,requestHandler);
            } else {
                client = Exchangers.connect(url ,requestHandler);
            }
        } catch (RemotingException e) {
            throw new RpcException("Fail to create remoting client for service(" + url
                    + "): " + e.getMessage(), e);
        }
        return client;
    }

该方法先直接构造一个DubboInvoker类型的对象，其中获取客户端的参数调用了方法getClients(url)。看是否配置了参数connections，若未配置或配置为0则表示共享客户端链接，若是不共享则直接建立一个新的客户端对象，不然得到已经共享的链接，而且返回一个建立包装器ReferenceCountExchangeClient的客户端实例，该实例会记录被引用次数，最终的方法仍是调用目标的client对象。异步

初始化一个全新的Client对象的方法是核心，它也是先配置一些默认的参数，若是配置参数lazy则表示延迟建立客户端链接，则直接返回一个LazyConnectExchangeClient对象，该对象也是ExchangeClient的包装器对象，它会在请求的时候先检查链接，若未建立链接则会先建立链接。最后调用client = Exchangers.connect(url ,requestHandler);将url绑定到请求处理器requestHandler上。async

DubboInvoker

该类是消费者dubbo协议的执行器。它处理了dubbo协议在客户端调用远程接口的逻辑实现。核心方法是doInvoke，咱们重点看看这个方法的实现。ide

@Override
    protected Result doInvoke(final Invocation invocation) throws Throwable {
        RpcInvocation inv = (RpcInvocation) invocation;
        final String methodName = RpcUtils.getMethodName(invocation);
        inv.setAttachment(Constants.PATH_KEY, getUrl().getPath());
        inv.setAttachment(Constants.VERSION_KEY, version);
        
        ExchangeClient currentClient;
        if (clients.length == 1) {
            currentClient = clients[0];
        } else {
            currentClient = clients[index.getAndIncrement() % clients.length];
        }
        try {
            boolean isAsync = RpcUtils.isAsync(getUrl(), invocation);
            boolean isOneway = RpcUtils.isOneway(getUrl(), invocation);
            int timeout = getUrl().getMethodParameter(methodName, Constants.TIMEOUT_KEY,Constants.DEFAULT_TIMEOUT);
            if (isOneway) {
            	boolean isSent = getUrl().getMethodParameter(methodName, Constants.SENT_KEY, false);
                currentClient.send(inv, isSent);
                RpcContext.getContext().setFuture(null);
                return new RpcResult();
            } else if (isAsync) {
            	ResponseFuture future = currentClient.request(inv, timeout) ;
                RpcContext.getContext().setFuture(new FutureAdapter<Object>(future));
                return new RpcResult();
            } else {
            	RpcContext.getContext().setFuture(null);
                return (Result) currentClient.request(inv, timeout).get();
            }
        } catch (TimeoutException e) {
            throw new RpcException(RpcException.TIMEOUT_EXCEPTION, "Invoke remote method timeout. method: " + invocation.getMethodName() + ", provider: " + getUrl() + ", cause: " + e.getMessage(), e);
        } catch (RemotingException e) {
            throw new RpcException(RpcException.NETWORK_EXCEPTION, "Failed to invoke remote method: " + invocation.getMethodName() + ", provider: " + getUrl() + ", cause: " + e.getMessage(), e);
        }
    }

首先客户端支持多个链接调用服务，这个能够经过参数设置，会轮询链接去调用服务。支持三种调用方式，分别是oneway（单向调用）、async（异步）和sync（同步），这个都是能够经过url参数指定，经过客户端对应的方法去调用服务端的服务。性能