dubbo源码分析系列——dubbo-rpc-default模块源码分析

扫码关注公众号:Java 技术驿站

发送:vip
将链接复制到本浏览器,永久解锁本站全部文章

【公众号:Java 技术驿站】 【加作者微信交流技术,拉技术群】

作者:杨武兵

出处:https://my.oschina.net/ywbrj042?tab=newest&catalogId=3594617


简化类图

从图中可以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。

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。

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. 通过url获得该服务的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,需要后续深究。
        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,需要进入深究。
        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。我们进入该方法看看。

private void openServer(URL url) {
        // find server.
        String key = url.getAddress();
        //client 也可以暴露一个只有server可以调用的服务。
        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);
            }
        }
    }

该方法是获得url的地址,通过地址找到对应的server,若已经有相同的地址则无需构造新的server,只需要直接使用,只就起到了缓存server的作用,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参数可以禁止发布远程服务,只能本地调用。具体意义不是十分清楚。继续进入方法:createServer(url)

```java 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;
}

该方法先增加了一些默认的参数,比如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上获得绑定的服务器,Exchangers是网络通讯模块dubbo-remoting-api中定义的,详细的含义,等我们分析该模块再了解。我们猜测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,我们进入该对象的定义看看。 ```java 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); //如果是callback 需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讯的抽象,是一个通讯处理类,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对象获得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做了响应的处理,包括:received、connected和disconnected等事件。

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){
        //是否共享连接
        boolean service_share_connect = false;
        int connections = url.getParameter(Constants.CONNECTIONS_KEY, 0);
        //如果connections不配置,则共享连接,否则每服务每连接
        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;
    }

    /**
     *获取共享连接
     */
    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;
    }

    /**
     * 创建新连接.
     */
    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,暂时不允许使用
        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 {
            //设置连接应该是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则表示共享客户端连接,如果不共享则直接创建一个新的客户端对象,否则获得已经共享的连接,并且返回一个创建包装器ReferenceCountExchangeClient的客户端实例,该实例会记录被引用次数,最终的方法还是调用目标的client对象。

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,如果配置参数lazy则表示延迟创建客户端连接,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连接,若未创建连接则会先创建连接。最后调用client = Exchangers.connect(url ,requestHandler);将url绑定到请求处理器requestHandler上。

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,我们重点看看这个方法的实现。

```java @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连接调用服务,这个可以通过参数设置,会轮询连接去调用服务。支持三种调用方式,分别是oneway(单向调用)、async(异步)和sync(同步),这个都是可以通过url参数指定,通过客户端对应的方法去调用服务端的服务。

next

可以看出来,我们有大量的接口和抽象类来自于dubbo-remoting-api模块,我们的疑问都在这里,接下来我们研究该模块才能解决我们的很多疑惑。

赞(0) 打赏
版权归原创作者所有,任何形式的转载请联系博主:daming_90:Java 技术驿站 » dubbo源码分析系列——dubbo-rpc-default模块源码分析

  • 暂无文章

评论 抢沙发

  • 昵称 (必填)
  • 邮箱 (必填)
  • 网址

觉得文章有用就打赏一下文章作者

支付宝扫一扫打赏

微信扫一扫打赏