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https://issues.apache.org/jira/browse/HADOOP-3130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12584154#action_12584154
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Runping Qi commented on HADOOP-3130:
------------------------------------
>From timing point view,
the following two are equivalent:
{code}
connect( , N_units_timeout);
{code}
{code}
lastException=null;
lastTime=-1;
for (int i = 0; i < N; i++) {
try {
connect( , N_units_timeout);
break;
}
catch (IOException e) {
lastException = e;
lastTime = i;
}
}
if (lastTime==N-1) throw lastException;
{code}
But the second one has a much stronger liveness.
> Shuffling takes too long to get the last map output.
> ----------------------------------------------------
>
> Key: HADOOP-3130
> URL: https://issues.apache.org/jira/browse/HADOOP-3130
> Project: Hadoop Core
> Issue Type: Bug
> Reporter: Runping Qi
> Attachments: HADOOP-3130.patch, shuffling.log
>
>
> I noticed that towards the end of shufflling, the map output fetcher of the
> reducer backs off too aggressively.
> I attach a fraction of one reduce log of my job.
> Noticed that the last map output was not fetched in 2 minutes.
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