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https://issues.apache.org/jira/browse/HIVE-12790?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15088083#comment-15088083
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Thejas M Nair commented on HIVE-12790:
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bq. The proposed fix calls SessionState.close() from its run() method, so it
should only close it when executing in a new thread.
SeesionState is needed beyond the lifetime of the current query execution, as
it represents a session.
bq. But shouldn't the thread local variables be cleaned up when a session is
closed?
We don't maintain a session to threads/threadlocal mapping. It should ideally
be closed when the thread is being released.
Also, Hive.get() is called from many places outside of SessionState as well.
You can call Hive.closeCurrent() in the place where you added the call to
ss.close to fix this.
> Metastore connection leaks in HiveServer2
> -----------------------------------------
>
> Key: HIVE-12790
> URL: https://issues.apache.org/jira/browse/HIVE-12790
> Project: Hive
> Issue Type: Bug
> Components: HiveServer2
> Affects Versions: 1.1.0
> Reporter: Naveen Gangam
> Assignee: Naveen Gangam
> Attachments: HIVE-12790.patch, snippedLog.txt
>
>
> HiveServer2 keeps opening new connections to HMS each time it launches a
> task. These connections do not appear to be closed when the task completes
> thus causing a HMS connection leak. "lsof" for the HS2 process shows
> connections to port 9083.
> {code}
> 2015-12-03 04:20:56,352 INFO [HiveServer2-Background-Pool: Thread-424756()]:
> ql.Driver (SessionState.java:printInfo(558)) - Launching Job 11 out of 41
> 2015-12-03 04:20:56,354 INFO [Thread-405728()]: hive.metastore
> (HiveMetaStoreClient.java:open(311)) - Trying to connect to metastore with
> URI thrift://<anonymizedURL>:9083
> 2015-12-03 04:20:56,360 INFO [Thread-405728()]: hive.metastore
> (HiveMetaStoreClient.java:open(351)) - Opened a connection to metastore,
> current connections: 14824
> 2015-12-03 04:20:56,360 INFO [Thread-405728()]: hive.metastore
> (HiveMetaStoreClient.java:open(400)) - Connected to metastore.
> ....
> 2015-12-03 04:21:06,355 INFO [HiveServer2-Background-Pool: Thread-424756()]:
> ql.Driver (SessionState.java:printInfo(558)) - Launching Job 12 out of 41
> 2015-12-03 04:21:06,357 INFO [Thread-405756()]: hive.metastore
> (HiveMetaStoreClient.java:open(311)) - Trying to connect to metastore with
> URI thrift://<anonymizedURL>:9083
> 2015-12-03 04:21:06,362 INFO [Thread-405756()]: hive.metastore
> (HiveMetaStoreClient.java:open(351)) - Opened a connection to metastore,
> current connections: 14825
> 2015-12-03 04:21:06,362 INFO [Thread-405756()]: hive.metastore
> (HiveMetaStoreClient.java:open(400)) - Connected to metastore.
> ...
> 2015-12-03 04:21:08,357 INFO [HiveServer2-Background-Pool: Thread-424756()]:
> ql.Driver (SessionState.java:printInfo(558)) - Launching Job 13 out of 41
> 2015-12-03 04:21:08,360 INFO [Thread-405782()]: hive.metastore
> (HiveMetaStoreClient.java:open(311)) - Trying to connect to metastore with
> URI thrift://<anonymizedURL>:9083
> 2015-12-03 04:21:08,364 INFO [Thread-405782()]: hive.metastore
> (HiveMetaStoreClient.java:open(351)) - Opened a connection to metastore,
> current connections: 14826
> 2015-12-03 04:21:08,365 INFO [Thread-405782()]: hive.metastore
> (HiveMetaStoreClient.java:open(400)) - Connected to metastore.
> ...
> {code}
> The TaskRunner thread starts a new SessionState each time, which creates a
> new connection to the HMS (via Hive.get(conf).getMSC()) that is never closed.
> Even SessionState.close(), currently not being called by the TaskRunner
> thread, does not close this connection.
> Attaching a anonymized log snippet where the number of HMS connections
> reaches north of 25000+ connections.
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