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https://issues.apache.org/jira/browse/MAPREDUCE-5958?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14052926#comment-14052926
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Hadoop QA commented on MAPREDUCE-5958:
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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/12654179/HADOOP-5958-v2.patch
against trunk revision .
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:red}-1 tests included{color}. The patch doesn't appear to include
any new or modified tests.
Please justify why no new tests are needed for this
patch.
Also please list what manual steps were performed to
verify this patch.
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:green}+1 javadoc{color}. There were no new javadoc 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-core.
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/4715//testReport/
Console output:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/4715//console
This message is automatically generated.
> Wrong reduce task progress if map output is compressed
> ------------------------------------------------------
>
> Key: MAPREDUCE-5958
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5958
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 2.2.0, 2.3.0, 2.2.1, 2.4.0, 2.4.1
> Reporter: Emilio Coppa
> Priority: Minor
> Labels: progress, reduce
> Fix For: 2.4.1
>
> Attachments: HADOOP-5958-v2.patch
>
>
> If the map output is compressed (_mapreduce.map.output.compress_ set to
> _true_) then the reduce task progress may be highly underestimated.
> In the reduce phase (but also in the merge phase), the progress of a reduce
> task is computed as the ratio between the number of processed bytes and the
> number of total bytes. But:
> - the number of total bytes is computed by summing up the uncompressed
> segment sizes (_Merger.Segment.getRawDataLength()_)
> - the number of processed bytes is computed by exploiting the position of the
> current _IFile.Reader_ (using _IFile.Reader.getPosition()_) but this may
> refer to the position in the underlying on disk file (which may be compressed)
> Thus, if the map outputs are compressed then the progress may be
> underestimated (e.g., only 1 map output ondisk file, the compressed file is
> 25% of its original size, then the reduce task progress during the reduce
> phase will range between 0 and 0.25 and then artificially jump to 1.0).
> Attached there is a patch: the number of processed bytes is now computed by
> exploiting _IFile.Reader.bytesRead_ (if the the reader is in memory, then
> _getPosition()_ already returns exactly this field).
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