[jira] [Commented] (HIVE-20682) Async query execution can potentially fail if shared sessionHive is closed by master thread.

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-20682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16671872#comment-16671872 ] 

ASF GitHub Bot commented on HIVE-20682:
---------------------------------------

Github user sankarh closed the pull request at:

    https://github.com/apache/hive/pull/452


> Async query execution can potentially fail if shared sessionHive is closed by master thread.
> --------------------------------------------------------------------------------------------
>
>                 Key: HIVE-20682
>                 URL: https://issues.apache.org/jira/browse/HIVE-20682
>             Project: Hive
>          Issue Type: Bug
>          Components: HiveServer2
>    Affects Versions: 3.1.0, 4.0.0
>            Reporter: Sankar Hariappan
>            Assignee: Sankar Hariappan
>            Priority: Major
>              Labels: pull-request-available
>         Attachments: HIVE-20682.01.patch, HIVE-20682.02.patch, HIVE-20682.03.patch, HIVE-20682.04.patch
>
>
> *Problem description:*
> The master thread initializes the *sessionHive* object in *HiveSessionImpl* class when we open a new session for a client connection and by default all queries from this connection shares the same sessionHive object. 
> If the master thread executes a *synchronous* query, it closes the sessionHive object (referred via thread local hiveDb) if  {{Hive.isCompatible}} returns false and sets new Hive object in thread local HiveDb but doesn't change the sessionHive object in the session. Whereas, *asynchronous* query execution via async threads never closes the sessionHive object and it just creates a new one if needed and sets it as their thread local hiveDb.
> So, the problem can happen in the case where an *asynchronous* query is being executed by async threads refers to sessionHive object and the master thread receives a *synchronous* query that closes the same sessionHive object. 
> Also, each query execution overwrites the thread local hiveDb object to sessionHive object which potentially leaks a metastore connection if the previous synchronous query execution re-created the Hive object.
> *Possible Fix:*
> The *sessionHive* object could be shared my multiple threads and so it shouldn't be allowed to be closed by any query execution threads when they re-create the Hive object due to changes in Hive configurations. But the Hive objects created by query execution threads should be closed when the thread exits.
> So, it is proposed to have an *isAllowClose* flag (default: *true*) in Hive object which should be set to *false* for *sessionHive* and would be forcefully closed when the session is closed or released.
> cc [~pvary]



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