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https://issues.apache.org/jira/browse/MAPREDUCE-4772?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13492620#comment-13492620
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Hadoop QA commented on MAPREDUCE-4772:
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{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12552513/MR-4772-trunk.txt
against trunk revision .
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:green}+1 tests included{color}. The patch appears to include 2 new
or modified test files.
{color:red}-1 javac{color}. The applied patch generated 2031 javac
compiler warnings (more than the trunk's current 2025 warnings).
{color:green}+1 javadoc{color}. The javadoc tool did not generate any
warning messages.
{color:green}+1 eclipse:eclipse{color}. The patch built with
eclipse:eclipse.
{color:green}+1 findbugs{color}. The patch does not introduce any new
Findbugs (version 1.3.9) warnings.
{color:green}+1 release audit{color}. The applied patch does not increase
the total number of release audit warnings.
{color:green}+1 core tests{color}. The patch passed unit tests in
hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app
hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core.
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/2993//testReport/
Javac warnings:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/2993//artifact/trunk/patchprocess/diffJavacWarnings.txt
Console output:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/2993//console
This message is automatically generated.
> Fetch failures can take way too long for a map to be restarted
> --------------------------------------------------------------
>
> Key: MAPREDUCE-4772
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4772
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mrv2
> Affects Versions: 0.23.4
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Priority: Critical
> Attachments: MR-4772-0.23.txt, MR-4772-trunk.txt
>
>
> In one particular case we saw a NM go down at just the right time, that most
> of the reducers got the output of the map tasks, but not all of them.
> The ones that failed to get the output reported to the AM rather quickly that
> they could not fetch from the NM, but because the other reducers were still
> running the AM would not relaunch the map task because there weren't more
> than 50% of the running reducers that had reported fetch failures. Then
> because of the exponential back-off for fetches on the reducers it took until
> 1 hour 45 min for the reduce tasks to hit another 10 fetch failures and
> report in again. At that point the other reducers had finished and the job
> relaunched the map task. If the reducers had still been running at 1:45 I
> have no idea how long it would have taken for each of the tasks to get to 30
> fetch failures.
> We need to trigger the map based off of percentage of reducers shuffling, not
> percentage of reducers running, we also need to have a maximum limit of the
> back off, so that we don't ever have the reducer waiting for days to try and
> fetch map output.
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