Zhijie Shen created HADOOP-10794:
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             Summary: A hadoop cluster needs clock synchronization
                 Key: HADOOP-10794
                 URL: https://issues.apache.org/jira/browse/HADOOP-10794
             Project: Hadoop Common
          Issue Type: Bug
            Reporter: Zhijie Shen


As a distributed system, a hadoop cluster wants the clock on all the 
participating hosts synchronized. Otherwise, some problems might happen. For 
example, in MAPREDUCE-5940, due to the clock on the host for the task container 
falls behind that on the host of the AM container, the computed elapsed time 
(the diff between the timestamps produced on two hosts) becomes negative.

In MAPREDUCE-5940, we tried to mask the negative elapsed time. However, we 
should seek for a decent long term solution, such as providing mechanism to do 
and check clock synchronization.



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