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From "Wei-Chiu Chuang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11738) Hedged pread takes more time when block moved from initial locations
Date Fri, 11 Aug 2017 05:05:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16122848#comment-16122848
] 

Wei-Chiu Chuang commented on HDFS-11738:
----------------------------------------

Thanks [~vinayrpet] for the patch! I haven't reviewed the patch fully, but looking at the
patch, this jira is the superset of HDFS-11303.
Perhaps we should give up HDFS-11303 and focus on this one.

[~jzhuge] how do you think?

> Hedged pread takes more time when block moved from initial locations
> --------------------------------------------------------------------
>
>                 Key: HDFS-11738
>                 URL: https://issues.apache.org/jira/browse/HDFS-11738
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs-client
>            Reporter: Vinayakumar B
>            Assignee: Vinayakumar B
>         Attachments: HDFS-11738-01.patch, HDFS-11738-02.patch
>
>
> Scenario : 
> Same as HDFS-11708.
> During Hedge read, 
> 1. First two locations fails to read the data in hedged mode.
> 2. chooseData refetches locations and adds a future to read from DN3.
> 3. after adding future to DN3, main thread goes for refetching locations in loop and
stucks there till all 3  retries to fetch locations exhausted, which consumes ~20 seconds
with exponential retry time.



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