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From "Carl Steinbach (JIRA)" <>
Subject [jira] [Updated] (HIVE-3098) Memory leak from large number of FileSystem instances in FileSystem.CACHE. (Must cache UGIs.)
Date Thu, 07 Jun 2012 23:35:23 GMT


Carl Steinbach updated HIVE-3098:

    Status: Open  (was: Patch Available)

@Mithun: Please post a review request on reviewboard or phabricator. Thanks.
> Memory leak from large number of FileSystem instances in FileSystem.CACHE. (Must cache
> ---------------------------------------------------------------------------------------------
>                 Key: HIVE-3098
>                 URL:
>             Project: Hive
>          Issue Type: Bug
>          Components: Shims
>    Affects Versions: 0.9.0
>         Environment: Running with Hadoop / 1.0.x with security turned on.
>            Reporter: Mithun Radhakrishnan
>            Assignee: Mithun Radhakrishnan
>         Attachments: HIVE-3098.patch
> The problem manifested from stress-testing HCatalog 0.4.1 (as part of testing the Oracle
> The HCatalog server ran out of memory (-Xmx2048m) when pounded by 60-threads, in under
24 hours. The heap-dump indicates that hadoop::FileSystem.CACHE had 1000000 instances of FileSystem,
whose combined retained-mem consumed the entire heap.
> It boiled down to hadoop::UserGroupInformation::equals() being implemented such that
the "Subject" member is compared for equality ("=="), and not equivalence (".equals()"). This
causes equivalent UGI instances to compare as unequal, and causes a new FileSystem instance
to be created and cached.
> The UGI.equals() is so implemented, incidentally, as a fix for yet another problem (HADOOP-6670);
so it is unlikely that that implementation can be modified.
> The solution for this is to check for UGI equivalence in HCatalog (i.e. in the Hive metastore),
using an cache for UGI instances in the shims.
> I have a patch to fix this. I'll upload it shortly. I just ran an overnight test to confirm
that the memory-leak has been arrested.

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