Aihua Xu created HIVE-24171:
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Summary: Support HDFS reads from observer NameNodes
Key: HIVE-24171
URL: https://issues.apache.org/jira/browse/HIVE-24171
Project: Hive
Issue Type: New Feature
Components: Hive
Affects Versions: 3.0.0
Reporter: Aihua Xu
Assignee: Aihua Xu
HDFS-12943 introduces the consistent reads from observer NameNodes which can
boost the read performance and reduces the overloads on active NameNodes.
To take advantage of this feature, the clients are required to make a msync()
call after writing the files or before reading the files since observer
NameNodes could have the stale data for a small window.
Hive needs to make msync() call to HDFS in some places, e.g., 1) after
generating the plan files - map.xml and reduce.xml so they can get used later
by executors; 2) after the intermediate files are generated so they can get
used by later stages or HS2.
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