Task.TaskReporter.done method blocked for some time when task is finishing
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                 Key: MAPREDUCE-3612
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3612
             Project: Hadoop Map/Reduce
          Issue Type: Bug
            Reporter: Binglin Chang


We recently have done some tests to evaluate performances of different Hadoop versions(1.0, 0.23, Baidu internal version), and found some weird results. One of them is in 1.0 Task.TaskReporter.done() takes too much time, about 2s, this is bad for small tasks. After reviewing source code and add some log, the following code block Task.TaskReporter.done

src/mapred/org/apache/hadoop/mapred/Task.java

 658           try {
 659             Thread.sleep(PROGRESS_INTERVAL);
 660           }


 723     public void stopCommunicationThread() throws InterruptedException {
 724       // Updating resources specified in ResourceCalculatorPlugin
 725       if (pingThread != null) {
 726         synchronized(lock) {
 727           while(!done) {
 728             lock.wait();
 729           }
 730         }
 731         pingThread.interrupt();
 732         pingThread.join();
 733       }
 734     }

Originally line 724-730 don't exists, I don't know why it is added. If it is needed, we can replace Thread.sleep with Object.wait(timeout) and Object.notify instead, so it won't block.




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