Amruth S created HIVE-22165:
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Summary: 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: 2.3.2, 2.1.0
Reporter: Amruth S
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, a
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.
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