[jira] [Assigned] (HIVE-24171) Support HDFS reads from observer NameNodes

["Aihua Xu (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-24171?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aihua Xu reassigned HIVE-24171:
-------------------------------


> 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
>            Priority: Major
>
> 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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