Dubbo原始碼解析之服務端接收訊息

寒武沒有紀發表於2018-11-04
原始碼服務端

準備

dubbo 版本：2.5.4

服務端接收訊息流程

Handler鏈路

DubboProtocol

private ExchangeServer createServer(URL url) {
    url = url.addParameterIfAbsent("channel.readonly.sent", Boolean.TRUE.toString());
    url = url.addParameterIfAbsent("heartbeat", String.valueOf(60000));
    String str = url.getParameter("server", "netty");
    if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) {
        throw new RpcException("Unsupported server type: " + str + ", url: " + url);
    } else {
        url = url.addParameter("codec", Version.isCompatibleVersion() ? "dubbo1compatible" : "dubbo");

        ExchangeServer server;
        try {
            // requestHandler -> new ExchangeHandlerAdapter() {}
            server = Exchangers.bind(url, this.requestHandler);
        } catch (RemotingException var5) {
            throw new RpcException("Fail to start server(url: " + url + ") " + var5.getMessage(), var5);
        }

        str = url.getParameter("client");
        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;
    }
}

HeaderExchanger

public ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException {
    // DecodeHandler(HeaderExchangeHandler(ExchangeHandlerAdapter))
    return new HeaderExchangeServer(Transporters.bind(url, new DecodeHandler(new HeaderExchangeHandler(handler))));
}

NettyServer

public NettyServer(URL url, ChannelHandler handler) throws RemotingException{
    super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));
}

ChannelHandlers

protected ChannelHandler wrapInternal(ChannelHandler handler, URL url) {
    // extension = ExtensionLoader.getExtensionLoader(Dispatcher.class).getAdaptiveExtension()
    // extension = AllDispatcher
    return new MultiMessageHandler(new HeartbeatHandler(((Dispatcher)ExtensionLoader.getExtensionLoader(Dispatcher.class).getAdaptiveExtension()).dispatch(handler, url)));
}

AllDispatcher

public class AllDispatcher implements Dispatcher {
    public static final String NAME = "all";
    public ChannelHandler dispatch(ChannelHandler handler, URL url) {
        // AllChannelHandler
        return new AllChannelHandler(handler, url);
    }
}

所以，服務端完整的 handler 鏈路為：

MultiMessageHandler -> HeartbeatHandler -> AllChannelHandler -> DecodeHandler -> HeaderExchangeHandler -> ExchangeHandlerAdapter

接收訊息流程

NettyHandler

public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
    NettyChannel channel = NettyChannel.getOrAddChannel(ctx.getChannel(), this.url, this.handler);

    try {
        // 呼叫MultiMessageHandler處理
        this.handler.received(channel, e.getMessage());
    } finally {
        NettyChannel.removeChannelIfDisconnected(ctx.getChannel());
    }
}

MultiMessageHandler

public void received(Channel channel, Object message) throws RemotingException {
    if (message instanceof MultiMessage) {
        MultiMessage list = (MultiMessage)message;
        for(Object obj : list) {
            handler.received(channel, obj);
        }
    } else {
        // 呼叫HeartbeatHandler處理
        handler.received(channel, message);
    }
}

HeartbeatHandler

public void received(Channel channel, Object message) throws RemotingException {
    setReadTimestamp(channel);
    if (isHeartbeatRequest(message)) {
        Request req = (Request) message;
        if (req.isTwoWay()) {
            Response res = new Response(req.getId(), req.getVersion());
            res.setEvent(Response.HEARTBEAT_EVENT);
            channel.send(res);
            if (logger.isInfoEnabled()) {
                int heartbeat = channel.getUrl().getParameter(Constants.HEARTBEAT_KEY, 0);
                if(logger.isDebugEnabled()) {
                    logger.debug("Received heartbeat from remote channel " + channel.getRemoteAddress()
                                    + ", cause: The channel has no data-transmission exceeds a heartbeat period"
                                    + (heartbeat > 0 ? ": " + heartbeat + "ms" : ""));
                }
         }
        }
        return;
    }
    if (isHeartbeatResponse(message)) {
        if (logger.isDebugEnabled()) {
           logger.debug(
                new StringBuilder(32)
                    .append("Receive heartbeat response in thread ")
                    .append(Thread.currentThread().getName())
                    .toString());
        }
        return;
    }
    // 呼叫AllChannelHandler處理
    handler.received(channel, message);
}

AllChannelHandler

public void received(Channel channel, Object message) throws RemotingException {
    ExecutorService cexecutor = getExecutorService();
    try {
        cexecutor.execute(new ChannelEventRunnable(channel, handler, ChannelState.RECEIVED, message));
    } catch (Throwable t) {
        throw new ExecutionException(message, channel, getClass() + " error when process received event .", t);
    }
}

ChannelEventRunnable

public void run() {
    switch (state) {
        case CONNECTED:
            try{
                handler.connected(channel);
            }catch (Exception e) {
                logger.warn("ChannelEventRunnable handle " + state + " operation error, channel is " + channel, e);
            }
            break;
        case DISCONNECTED:
            try{
                handler.disconnected(channel);
            }catch (Exception e) {
                logger.warn("ChannelEventRunnable handle " + state + " operation error, channel is " + channel, e);
            }
            break;
        case SENT:
            try{
                handler.sent(channel,message);
            }catch (Exception e) {
                logger.warn("ChannelEventRunnable handle " + state + " operation error, channel is " + channel
                        + ", message is "+ message,e);
            }
            break;
        case RECEIVED:
            try{
                // 呼叫DecodeHandler處理
                handler.received(channel, message);
            }catch (Exception e) {
                logger.warn("ChannelEventRunnable handle " + state + " operation error, channel is " + channel
                        + ", message is "+ message,e);
            }
            break;
        case CAUGHT:
            try{
                handler.caught(channel, exception);
            }catch (Exception e) {
                logger.warn("ChannelEventRunnable handle " + state + " operation error, channel is "+ channel
                        + ", message is: " + message + ", exception is " + exception,e);
            }
            break;
        default:
            logger.warn("unknown state: " + state + ", message is " + message);
    }
}

DecodeHandler

public void received(Channel channel, Object message) throws RemotingException {
    if (message instanceof Decodeable) {
        decode(message);
    }

    if (message instanceof Request) {
        decode(((Request)message).getData());
    }

    if (message instanceof Response) {
        decode( ((Response)message).getResult());
    }
	// 呼叫HeaderExchangeHandler處理
    handler.received(channel, message);
}

HeaderExchangeHandler

public void received(Channel channel, Object message) throws RemotingException {
    channel.setAttribute(KEY_READ_TIMESTAMP, System.currentTimeMillis());
    ExchangeChannel exchangeChannel = HeaderExchangeChannel.getOrAddChannel(channel);
    try {
        if (message instanceof Request) {
            // handle request.
            Request request = (Request) message;
            if (request.isEvent()) {
                handlerEvent(channel, request);
            } else {
                if (request.isTwoWay()) {
                    // 處理請求
                    Response response = handleRequest(exchangeChannel, request);
                    channel.send(response);
                } else {
                    handler.received(exchangeChannel, request.getData());
                }
            }
        } else if (message instanceof Response) {
            handleResponse(channel, (Response) message);
        } else if (message instanceof String) {
            if (isClientSide(channel)) {
                Exception e = new Exception("Dubbo client can not supported string message: " + message + " in channel: " + channel + ", url: " + channel.getUrl());
                logger.error(e.getMessage(), e);
            } else {
                String echo = handler.telnet(channel, (String) message);
                if (echo != null && echo.length() > 0) {
                    channel.send(echo);
                }
            }
        } else {
            handler.received(exchangeChannel, message);
        }
    } finally {
        HeaderExchangeChannel.removeChannelIfDisconnected(channel);
    }
}

// HeaderExchangeHandler
Response handleRequest(ExchangeChannel channel, Request req) throws RemotingException {
    Response res = new Response(req.getId(), req.getVersion());
    if (req.isBroken()) {
        Object data = req.getData();

        String msg;
        if (data == null) msg = null;
        else if (data instanceof Throwable) msg = StringUtils.toString((Throwable) data);
        else msg = data.toString();
        res.setErrorMessage("Fail to decode request due to: " + msg);
        res.setStatus(Response.BAD_REQUEST);

        return res;
    }
    // find handler by message class.
    Object msg = req.getData();
    try {
        // handle data.
        Object result = handler.reply(channel, msg);
        res.setStatus(Response.OK);
        res.setResult(result);
    } catch (Throwable e) {
        res.setStatus(Response.SERVICE_ERROR);
        res.setErrorMessage(StringUtils.toString(e));
    }
    return res;
}

DubboProtocol 成員變數 requestHandler 匿名內部類實現

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 需要處理高版本呼叫低版本的問題
        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());
        // invoker -> Filter(Listener(InvokerDelegete(AbstractProxyInvoker (Wrapper.invokeMethod)))
        return invoker.invoke(inv);
    }
    throw new RemotingException(channel, "Unsupported request: " + message == null ? null : (message.getClass().getName() + ": " + message) + ", channel: consumer: " + channel.getRemoteAddress() + " --> provider: " + channel.getLocalAddress());
}

服務端接收訊息流程完成。

相關文章