You are viewing a plain text version of this content. The canonical link for it is here.
Posted to dev@hive.apache.org by "Ashutosh Chauhan (JIRA)" <ji...@apache.org> on 2012/07/11 09:09:35 UTC
[jira] [Commented] (HIVE-3098) Memory leak from large number of
FileSystem instances in FileSystem.CACHE. (Must cache UGIs.)
[ https://issues.apache.org/jira/browse/HIVE-3098?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13411287#comment-13411287 ]
Ashutosh Chauhan commented on HIVE-3098:
----------------------------------------
[~rohini] / [~mithun] : After reading through all the comments, my recommendation is to instead of adding more code (and complexity) in Hive to workaround underlying Filesystem issue, lets just disable the fs.cache via config parameter because:
* By disabling cache we are not making anything worse then its today, since we are already unable to reuse FS objects without this patch.
* Disabling cache will plug the memory leak by not filling FS cache.
* Once FSContext apis are declared stable for other projects to consume, we can switch over to those where the promise is that underlying problem is fixed.
> Memory leak from large number of FileSystem instances in FileSystem.CACHE. (Must cache UGIs.)
> ---------------------------------------------------------------------------------------------
>
> Key: HIVE-3098
> URL: https://issues.apache.org/jira/browse/HIVE-3098
> Project: Hive
> Issue Type: Bug
> Components: Shims
> Affects Versions: 0.9.0
> Environment: Running with Hadoop 20.205.0.3+ / 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 backend).
> 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.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira