[jira] Work started: (HADOOP-547) ReduceTaskRunner can miss sending hearbeats if no map output copy finishes within "mapred.task.timeout"

["Sanjay Dahiya (JIRA)" <ji...@apache.org>]

     [ http://issues.apache.org/jira/browse/HADOOP-547?page=all ]

Work on HADOOP-547 started by Sanjay Dahiya.

> ReduceTaskRunner can miss sending hearbeats if no map output copy finishes within "mapred.task.timeout"
> -------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-547
>                 URL: http://issues.apache.org/jira/browse/HADOOP-547
>             Project: Hadoop
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.6.2
>            Reporter: Sanjay Dahiya
>         Assigned To: Sanjay Dahiya
>
> In ReduceTaskRunner, main loop sending heartbeats waits on copyResults, which releases only if a copy thread finishes copying. This can cause good reduce tasks which are copying data to fail, if no map task output was copied within "mapred.task.timeout". 
> ReduceTaskRunner.java:490
>         try {
>           copyResults.wait();                      <=========== Calls unconditional wait. 
>         } catch (InterruptedException e) { }
> wait() should be with a timeout, possibly taskTimeout/2 after which it should send a hearbeat and go back to wait. 

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