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