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https://issues.apache.org/jira/browse/MAPREDUCE-6344?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Preston Koprivica updated MAPREDUCE-6344:
-----------------------------------------
Description:
We recently upgraded to MRv2 on YARN and have been noticing very inconsistent
classloading between the job submission client and the tasks as they start up.
I've tracked the issue to this method:
https://github.com/apache/hadoop/blob/release-2.5.0/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-common/src/main/java/org/apache/hadoop/mapreduce/v2/util/MRApps.java#L264
It appears that the classpath is simply "wild carded". According the javase
7&8 docs, the order of enumeration is not specified and may differ from moment
to moment [1][2]. This is a problem for applications that rely on strict
ordering, which the MRv1 DistributedCache used to provide.
I'm unable to track down all the things that are linked or landed into the $PWD
of the container, but assuming we can't account for all these things, a simple
solution could be to explicitly enumerate the files in DistributedCache -
similar to the "non jar" case [3] - and then add the "*" for passivity.
[1] http://docs.oracle.com/javase/7/docs/technotes/tools/windows/classpath.htm
[2]
http://docs.oracle.com/javase/8/docs/technotes/tools/windows/classpath.html#A1100762
[3]
https://github.com/apache/hadoop/blob/release-2.5.0/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-common/src/main/java/org/apache/hadoop/mapreduce/v2/util/MRApps.java#L270
was:
We recently upgraded to MRv2 on YARN and have been noticing very inconsistent
classloading between the job submission client and the tasks as they start up.
I've tracked the issue to this method:
https://github.com/apache/hadoop/blob/release-2.5.0/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-common/src/main/java/org/apache/hadoop/mapreduce/v2/util/MRApps.java#L264
It appears that the classpath is simply "wild carded". According the javase
7&8 docs, the order of enumeration is not specified and may differ from moment
to moment [1][2]. This is a problem for applications that rely on strict
ordering, which the MRv1 DistributedCache used to honor.
I'm unable to track down all the things that are linked or landed into the
\$PWD of the container, but assuming we can't account for all these things, a
simple solution could be to explicitly enumerate the files in DistributedCache
- similar to the "non jar" case [3] - and then add the "*" for passivity.
[1] http://docs.oracle.com/javase/7/docs/technotes/tools/windows/classpath.htm
[2]
http://docs.oracle.com/javase/8/docs/technotes/tools/windows/classpath.html#A1100762
[3]
https://github.com/apache/hadoop/blob/release-2.5.0/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-common/src/main/java/org/apache/hadoop/mapreduce/v2/util/MRApps.java#L270
> Inconsistent classpath/classloading from DistributedCache archives
> ------------------------------------------------------------------
>
> Key: MAPREDUCE-6344
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6344
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 2.5.0, 2.6.0, 2.7.0, 2.5.1, 2.5.2
> Reporter: Preston Koprivica
>
> We recently upgraded to MRv2 on YARN and have been noticing very inconsistent
> classloading between the job submission client and the tasks as they start
> up.
> I've tracked the issue to this method:
> https://github.com/apache/hadoop/blob/release-2.5.0/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-common/src/main/java/org/apache/hadoop/mapreduce/v2/util/MRApps.java#L264
> It appears that the classpath is simply "wild carded". According the javase
> 7&8 docs, the order of enumeration is not specified and may differ from
> moment to moment [1][2]. This is a problem for applications that rely on
> strict ordering, which the MRv1 DistributedCache used to provide.
> I'm unable to track down all the things that are linked or landed into the
> $PWD of the container, but assuming we can't account for all these things, a
> simple solution could be to explicitly enumerate the files in
> DistributedCache - similar to the "non jar" case [3] - and then add the "*"
> for passivity.
> [1] http://docs.oracle.com/javase/7/docs/technotes/tools/windows/classpath.htm
> [2]
> http://docs.oracle.com/javase/8/docs/technotes/tools/windows/classpath.html#A1100762
> [3]
> https://github.com/apache/hadoop/blob/release-2.5.0/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-common/src/main/java/org/apache/hadoop/mapreduce/v2/util/MRApps.java#L270
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