dubbo超时异常

在调用dubbo服务时经常看到如下错误： Caused by: com.alibaba.dubbo.remoting.TimeoutException: Waiting server-side response timeout by scan timer.

源码分析

客户端调用远程服务时，本地会生成一个DefaultFuture，调用DefaultFuture.get()获取远程服务返回的结构,此方法获取锁，调用await方法，此时当前线程进入等待队列，此线程会有两种结果过：要么超时，抛出TimeOutException；如果被唤醒，则返回rpc的结果。 而这里的报错很明显是由于等待服务端返回结果时客户端超时异常，查看源码如下：

public class DefaultFuture implements ResponseFuture {    private static final Logger                   logger = LoggerFactory.getLogger(DefaultFuture.class);    private static final Map
    
            CHANNELS   = new ConcurrentHashMap
     
      ();    private static final Map
      
        FUTURES   = new ConcurrentHashMap
       
        ();    // invoke id.    private final long                            id;    private final Channel                         channel;        private final Request                         request;    private final int                             timeout;    private final Lock                            lock = new ReentrantLock();    private final Condition                       done = lock.newCondition();    private final long                            start = System.currentTimeMillis();    private volatile long                         sent;        private volatile Response                     response;    private volatile ResponseCallback             callback;    public DefaultFuture(Channel channel, Request request, int timeout){        this.channel = channel;        this.request = request;        this.id = request.getId();        this.timeout = timeout > 0 ? timeout : channel.getUrl().getPositiveParameter(Constants.TIMEOUT_KEY, Constants.DEFAULT_TIMEOUT);        // put into waiting map.        FUTURES.put(id, this);        CHANNELS.put(id, channel);    }        public Object get() throws RemotingException {        return get(timeout);    }    public Object get(int timeout) throws RemotingException {        if (timeout <= 0) {            timeout = Constants.DEFAULT_TIMEOUT;        }        if (! isDone()) {            long start = System.currentTimeMillis();            lock.lock();            try {                while (! isDone()) {                    done.await(timeout, TimeUnit.MILLISECONDS);                    if (isDone() || System.currentTimeMillis() - start > timeout) {                        break;                    }                }            } catch (InterruptedException e) {                throw new RuntimeException(e);            } finally {                lock.unlock();            }            if (! isDone()) {                throw new TimeoutException(sent > 0, channel, getTimeoutMessage(false));            }        }        return returnFromResponse();    }}
       
      
     
    

这里的超时时间设置的是1s

public static final int     DEFAULT_TIMEOUT                    = 1000;

解决方案

检查消费者配置查看是否配置总的超时时长，这里建议配置一个总的，我由于没配置导致使用的是默认配置使得超过1s就报错。

也可以在消费者端对每个服务自定义配置

这里也需要注意服务端也有一个超时时间

• 全局配置

• 服务配置

当客户端timeout值>服务端timeout值，会出现超时日志，但是仍然可以获取到结果。客户端timeout超时抛出异常时，有一个线程RemotingInvocationTimeoutScan会自动清理对应超时的Future。