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https://issues.apache.org/jira/browse/MAPREDUCE-7094?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16470536#comment-16470536
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Adam Szita commented on MAPREDUCE-7094:
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Thanks for taking a look [~pbacsko] and [~wilfreds]. That's right - only one CL
will be created when LocalJobRunner calls the {{makeClassLoader}} method and
right now there's no other class invoking it. If we don't expect this to be
changed in the near future we can indeed drop the HashSet part from the
solution. See my updated patch: [^MAPREDUCE-7094.2.patch]
> LocalDistributedCacheManager leaves classloaders open, which leaks FDs
> ----------------------------------------------------------------------
>
> Key: MAPREDUCE-7094
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-7094
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 2.6.0
> Reporter: Adam Szita
> Priority: Major
> Attachments: MAPREDUCE-7094.0.patch, MAPREDUCE-7094.1.patch,
> MAPREDUCE-7094.2.patch
>
>
> When a user starts a local mapred task from Hive's beeline, it will leave
> open file descriptors on the HS2 process (which runs the mapred task).
> I debugged this and saw that it is caused by LocalDistributedCacheManager
> class, which creates a new URLClassLoader, with a classpath for the two jars
> seen below. Somewhere down the line Loaders will be created in this
> URLClassLoader for these files effectively creating the FD's on the OS level.
> This is never cleaned up after execution, although
> LocalDistributedCacheManager removes the files, it will not close the
> ClassLoader, so FDs are left open although they point to deleted files at
> that time:
> {code:java}
> [root@host-1 ~]# lsof -p 14439 | grep hadoop-hive
> java 14439 hive DEL REG 8,1 3348748
> /tmp/hadoop-hive/mapred/local/1525789796610/hive-exec-core.jar
> java 14439 hive DEL REG 8,1 3348750
> /tmp/hadoop-hive/mapred/local/1525789796609/hive-exec-1.1.0-cdh5.13.4-SNAPSHOT-core.jar
> java 14439 hive 649r REG 8,1 8112438 3348750
> /tmp/hadoop-hive/mapred/local/1525789796609/hive-exec-1.1.0-cdh5.13.4-SNAPSHOT-core.jar
> (deleted)
> java 14439 hive 650r REG 8,1 8112438 3348748
> /tmp/hadoop-hive/mapred/local/1525789796610/hive-exec-core.jar (deleted)
> {code}
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