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From "Amruth S (Jira)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-22165) Synchronisation introduced by HIVE-14296 on SessionManager.closeSession introduces high latency in a busy hive server
Date Sat, 31 Aug 2019 15:03:00 GMT

     [ https://issues.apache.org/jira/browse/HIVE-22165?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Amruth S updated HIVE-22165:
----------------------------
    Description: 
HIVE-14296 introduces this [commit|https://github.com/apache/hive/commit/477a47d3b4b9e3da3c22465217c2024588f7f000] which
adds synchronization to SessionManager.closeSession.

And it looks like it is used only for logging purposes.

In a busy hive server where 5-10 sessions are created closed every second, an increase in
latency of any other downstream services (Zk, HDFS) causes a queueing effect (lot of threads
getting blocked on SessionManager.closeSession) creating an induced latency of 3-5 minutes
at times for just closing the session. 

Since the gauge (MetricsConstant.HS2_OPEN_SESSIONS) is already tracking the open session counts,
the synchronization (along with the additional logging) can be without any functionality losses.

  was:
HIVE-14296 introduces this [commit|https://github.com/apache/hive/commit/477a47d3b4b9e3da3c22465217c2024588f7f000] which
adds synchronization to SessionManager.closeSession.

And it looks like it is used only for logging purposes.

In a busy hive server where 5-10 sessions are created closed every second, an increase in
latency of any other downstream services (Zk, HDFS) causes a queueing effect (lot of threads
getting blocked on SessionManager.closeSession) creating an induced latency of 3-5 minutes
at times for just closing the session. 

Since the gauge (MetricsConstant.HS2_OPEN_SESSIONS) is already tracking the open session counts,
the synchronization (along with the additional logging) can be removed.


> Synchronisation introduced by HIVE-14296 on SessionManager.closeSession introduces high
latency in a busy hive server
> ---------------------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-22165
>                 URL: https://issues.apache.org/jira/browse/HIVE-22165
>             Project: Hive
>          Issue Type: Bug
>          Components: HiveServer2
>    Affects Versions: 2.1.0, 2.3.2
>            Reporter: Amruth S
>            Priority: Major
>
> HIVE-14296 introduces this [commit|https://github.com/apache/hive/commit/477a47d3b4b9e3da3c22465217c2024588f7f000] which
adds synchronization to SessionManager.closeSession.
> And it looks like it is used only for logging purposes.
> In a busy hive server where 5-10 sessions are created closed every second, an increase
in latency of any other downstream services (Zk, HDFS) causes a queueing effect (lot of threads
getting blocked on SessionManager.closeSession) creating an induced latency of 3-5 minutes
at times for just closing the session. 
> Since the gauge (MetricsConstant.HS2_OPEN_SESSIONS) is already tracking the open session
counts, the synchronization (along with the additional logging) can be without any functionality
losses.



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