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https://issues.apache.org/jira/browse/HADOOP-10794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14063901#comment-14063901
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Colin Patrick McCabe commented on HADOOP-10794:
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bq. I'm afraid each component may more or less have made the assumption that
clock is synchronized across the cluster.
Can you explain which components make this assumption, and what happens if it's
violated? So far the only example presented is statistics in YARN.
> 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 YARN-2251, 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 YARN-2251, 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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