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From "Bill Graham (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-1313) PigServer leaks memory over time
Date Mon, 22 Mar 2010 23:39:27 GMT

    [ https://issues.apache.org/jira/browse/PIG-1313?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12848442#action_12848442
] 

Bill Graham commented on PIG-1313:
----------------------------------

Thanks for the pointer to PIG-240. The patch included make it look like that bug is focusing
specifically on the LogicalPlan refactor. 

In my case I do need a multi-threaded PigServer instance. My VM is running a scheduler which
wakes up and invokes scripts periodically and it is possible that one script will be kicked
off while another is already running.  As a result, calling FileLocalizer.deleteTempFiles()
can cause problem. This is because the toDelete Stack and others are static.

One possible fix would be to bind a toDelete Stack to each thread local instance, or to make
FileLocalizer non-static. The later seems cleaner but would require modifying a lot more code.

> PigServer leaks memory over time
> --------------------------------
>
>                 Key: PIG-1313
>                 URL: https://issues.apache.org/jira/browse/PIG-1313
>             Project: Pig
>          Issue Type: Bug
>            Reporter: Bill Graham
>
> When {{PigServer}} runs it creates temporary files using the {{FileLocalizer.getTemporaryPath(..)}}.
This static method creates and returns a handle to a temporary file (as an instance of {{ElementDescriptor}}).
The {{ElementDescriptors}} returned by this method are kept on a static {{Stack}} named {{toDelete}}.
The items on {{toDelete}} get removed by the {{FileLocalizer.deleteTempFile()}} method.
> The only place in the code where I see {{FileLocalizer.deleteTempFile()}} called is in
the Main class. {{PigServer}} does not call that method though, so a long-running VM that
repeatedly uses instances of {{PigServer}} to run jobs will leak memory via {{toDelete}}.
> One suggested fix is to have {{PigServer.shutdown()}} call {{FileLocalizer.deleteTempFile()}},
but this would cause problems in a multi-threaded environment, since it seems {{ElementDescriptors}}
are pushed onto the {{toDelete}} stack before they're used, not once they're done with. With
this approach, running multiple instances of {{PigServer}} in separate threads could cause
one completed job to clobber the other's still-in-use temp files.

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