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https://issues.apache.org/jira/browse/HIVE-20600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17178191#comment-17178191
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Stamatis Zampetakis commented on HIVE-20600:
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Looking into another case we observed that in some cases the counter of current
connections was by far off from the reality verified via netstat. This is not
meant to say that there is no problem but before reaching out to conclusions it
would be to good to check the actual open connections via a util like netstat.
> Metastore connection leak
> -------------------------
>
> Key: HIVE-20600
> URL: https://issues.apache.org/jira/browse/HIVE-20600
> Project: Hive
> Issue Type: Bug
> Components: HiveServer2
> Affects Versions: 2.3.3
> Reporter: Damon Cortesi
> Priority: Major
> Attachments: HIVE-20600.patch, consume_threads.py
>
>
> Within the execute method of HiveServer2, there appears to be a connection
> leak. With fairly straightforward series of INSERT statements, the connection
> count in the logs continues to increase over time. Under certain loads, this
> can also consume all underlying threads of the Hive metastore and result in
> HS2 becoming unresponsive to new connections.
> The log below is the result of some python code executing a single insert
> statement, and then looping through a series of 10 more insert statements. We
> can see there's one dangling connection left open after each execution
> leaving us with 12 open connections (11 from the execute statements + 1 from
> HS2 startup).
> {code}
> 2018-09-19T17:14:32,108 INFO [main([])]: hive.metastore
> (HiveMetaStoreClient.java:open(481)) - Opened a connection to metastore,
> current connections: 1
> 2018-09-19T17:14:48,175 INFO [29049f74-73c4-4f48-9cf7-b4bfe524a85b
> HiveServer2-Handler-Pool: Thread-31([])]: hive.metastore
> (HiveMetaStoreClient.java:open(481)) - Opened a connection to metastore,
> current connections: 2
> 2018-09-19T17:15:05,543 INFO [HiveServer2-Background-Pool: Thread-36([])]:
> hive.metastore (HiveMetaStoreClient.java:close(564)) - Closed a connection to
> metastore, current connections: 1
> 2018-09-19T17:15:05,548 INFO [HiveServer2-Background-Pool: Thread-36([])]:
> hive.metastore (HiveMetaStoreClient.java:open(481)) - Opened a connection to
> metastore, current connections: 2
> 2018-09-19T17:15:05,932 INFO [HiveServer2-Background-Pool: Thread-36([])]:
> hive.metastore (HiveMetaStoreClient.java:close(564)) - Closed a connection to
> metastore, current connections: 1
> 2018-09-19T17:15:05,935 INFO [HiveServer2-Background-Pool: Thread-36([])]:
> hive.metastore (HiveMetaStoreClient.java:open(481)) - Opened a connection to
> metastore, current connections: 2
> 2018-09-19T17:15:06,123 INFO [HiveServer2-Background-Pool: Thread-36([])]:
> hive.metastore (HiveMetaStoreClient.java:close(564)) - Closed a connection to
> metastore, current connections: 1
> 2018-09-19T17:15:06,126 INFO [HiveServer2-Background-Pool: Thread-36([])]:
> hive.metastore (HiveMetaStoreClient.java:open(481)) - Opened a connection to
> metastore, current connections: 2
> ...
> 2018-09-19T17:15:20,626 INFO [29049f74-73c4-4f48-9cf7-b4bfe524a85b
> HiveServer2-Handler-Pool: Thread-31([])]: hive.metastore
> (HiveMetaStoreClient.java:open(481)) - Opened a connection to metastore,
> current connections: 12
> 2018-09-19T17:15:21,153 INFO [HiveServer2-Background-Pool: Thread-162([])]:
> hive.metastore (HiveMetaStoreClient.java:close(564)) - Closed a connection to
> metastore, current connections: 11
> 2018-09-19T17:15:21,155 INFO [HiveServer2-Background-Pool: Thread-162([])]:
> hive.metastore (HiveMetaStoreClient.java:open(481)) - Opened a connection to
> metastore, current connections: 12
> 2018-09-19T17:15:21,306 INFO [HiveServer2-Background-Pool: Thread-162([])]:
> hive.metastore (HiveMetaStoreClient.java:close(564)) - Closed a connection to
> metastore, current connections: 11
> 2018-09-19T17:15:21,308 INFO [HiveServer2-Background-Pool: Thread-162([])]:
> hive.metastore (HiveMetaStoreClient.java:open(481)) - Opened a connection to
> metastore, current connections: 12
> 2018-09-19T17:15:21,385 INFO [HiveServer2-Background-Pool: Thread-162([])]:
> hive.metastore (HiveMetaStoreClient.java:close(564)) - Closed a connection to
> metastore, current connections: 11
> 2018-09-19T17:15:21,387 INFO [HiveServer2-Background-Pool: Thread-162([])]:
> hive.metastore (HiveMetaStoreClient.java:open(481)) - Opened a connection to
> metastore, current connections: 12
> 2018-09-19T17:15:21,541 INFO [HiveServer2-Handler-Pool: Thread-31([])]:
> hive.metastore (HiveMetaStoreClient.java:open(481)) - Opened a connection to
> metastore, current connections: 13
> 2018-09-19T17:15:21,542 INFO [HiveServer2-Handler-Pool: Thread-31([])]:
> hive.metastore (HiveMetaStoreClient.java:close(564)) - Closed a connection to
> metastore, current connections: 12
> {code}
> Attached is a simple [impyla|https://github.com/cloudera/impyla] script that
> triggers the condition.
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