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Alibaba Dubbo框架同步调用原理分析-2

2015-02-01 00:00 429 查看

接上一篇，看一下Dubbo的相关代码

关键代码：

com.taobao.remoting.impl.DefaultClient.java //同步调用远程接口 public Object invokeWithSync(Object appRequest, RequestControl control) throws RemotingException, InterruptedException { byte protocol = getProtocol(control); if (!TRConstants.isValidProtocol(protocol)) { throw new RemotingException("Invalid serialization protocol [" + protocol + "] on invokeWithSync."); } ResponseFuture future = invokeWithFuture(appRequest, control); return future.get(); //获取结果时让当前线程等待，ResponseFuture其实就是前面说的callback } public ResponseFuture invokeWithFuture(Object appRequest, RequestControl control) { byte protocol = getProtocol(control); long timeout = getTimeout(control); ConnectionRequest request = new ConnectionRequest(appRequest); request.setSerializeProtocol(protocol); Callback2FutureAdapter adapter = new Callback2FutureAdapter(request); connection.sendRequestWithCallback(request, adapter, timeout); return adapter; }

Callback2FutureAdapter implements ResponseFuture public Object get() throws RemotingException, InterruptedException { synchronized (this) { // 旋锁 while (!isDone) { // 是否有结果了 wait(); //没结果是释放锁，让当前线程处于等待状态 } } if (errorCode == TRConstants.RESULT_TIMEOUT) { throw new TimeoutException("Wait response timeout, request[" + connectionRequest.getAppRequest() + "]."); } else if (errorCode > 0) { throw new RemotingException(errorMsg); } else { return appResp; } } 客户端收到服务端结果后，回调时相关方法，即设置isDone = true并notifyAll() public void handleResponse(Object _appResponse) { appResp = _appResponse; //将远程调用结果设置到callback中来 setDone(); } public void onRemotingException(int _errorType, String _errorMsg) { errorCode = _errorType; errorMsg = _errorMsg; setDone(); } private void setDone() { isDone = true; synchronized (this) { //获取锁，因为前面wait()已经释放了callback的锁了 notifyAll(); // 唤醒处于等待的线程 } }

com.taobao.remoting.impl.DefaultConnection.java // 用来存放请求和回调的MAP private final ConcurrentHashMap<Long, Object[]> requestResidents; //发送消息出去 void sendRequestWithCallback(ConnectionRequest connRequest, ResponseCallback callback, long timeoutMs) { long requestId = connRequest.getId(); long waitBegin = System.currentTimeMillis(); long waitEnd = waitBegin + timeoutMs; Object[] queue = new Object[4]; int idx = 0; queue[idx++] = waitEnd; queue[idx++] = waitBegin; //用于记录日志 queue[idx++] = connRequest; //用于记录日志 queue[idx++] = callback; requestResidents.put(requestId, queue); // 记录响应队列 write(connRequest); // 埋点记录等待响应的Map的大小 StatLog.addStat("TBRemoting-ResponseQueues", "size", requestResidents.size(), 1L); } public void write(final Object connectionMsg) { //mina里的IoSession.write()发送消息 WriteFuture writeFuture = ioSession.write(connectionMsg); // 注册FutureListener，当请求发送失败后，能够立即做出响应 writeFuture.addListener(new MsgWrittenListener(this, connectionMsg)); } /** * 在得到响应后，删除对应的请求队列，并执行回调 * 调用者：MINA线程 */ public void putResponse(final ConnectionResponse connResp) { final long requestId = connResp.getRequestId(); Object[] queue = requestResidents.remove(requestId); if (null == queue) { Object appResp = connResp.getAppResponse(); String appRespClazz = (null == appResp) ? "null" : appResp.getClass().getName(); StringBuilder sb = new StringBuilder(); sb.append("Not found response receiver for requestId=[").append(requestId).append("],"); sb.append("from [").append(connResp.getHost()).append("],"); sb.append("response type [").append(appRespClazz).append("]."); LOGGER.warn(sb.toString()); return; } int idx = 0; idx++; long waitBegin = (Long) queue[idx++]; ConnectionRequest connRequest = (ConnectionRequest) queue[idx++]; ResponseCallback callback = (ResponseCallback) queue[idx++]; // ** 把回调任务交给业务提供的线程池执行 ** Executor callbackExecutor = callback.getExecutor(); callbackExecutor.execute(new CallbackExecutorTask(connResp, callback)); long duration = System.currentTimeMillis() - waitBegin; // 实际读响应时间 logIfResponseError(connResp, duration, connRequest.getAppRequest()); }

CallbackExecutorTask static private class CallbackExecutorTask implements Runnable { final ConnectionResponse resp; final ResponseCallback callback; final Thread createThread; CallbackExecutorTask(ConnectionResponse _resp, ResponseCallback _cb) { resp = _resp; callback = _cb; createThread = Thread.currentThread(); } public void run() { // 预防这种情况：业务提供的Executor，让调用者线程来执行任务 if (createThread == Thread.currentThread() && callback.getExecutor() != DIYExecutor.getInstance()) { StringBuilder sb = new StringBuilder(); sb.append("The network callback task [" + resp.getRequestId() + "] cancelled, cause:"); sb.append("Can not callback task on the network io thhread."); LOGGER.warn(sb.toString()); return; } if (TRConstants.RESULT_SUCCESS == resp.getResult()) { callback.handleResponse(resp.getAppResponse()); //设置调用结果 } else { callback.onRemotingException(resp.getResult(), resp .getErrorMsg()); //处理调用异常 } } }

另外：
1，服务端在处理客户端的消息，然后再处理时，使用了线程池来并行处理，不用一个一个消息的处理
同样，客户端接收到服务端的消息，也是使用线程池来处理消息，再回调

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