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Alibaba Dubbo框架同步调用原理分析-2

2014-02-22 22:44 405 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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