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From "Vinayakumar B (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-11738) hedged pread takes more time when block moved from initial locations
Date Tue, 02 May 2017 11:17:04 GMT

     [ https://issues.apache.org/jira/browse/HDFS-11738?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vinayakumar B updated HDFS-11738:
---------------------------------
    Attachment: HDFS-11738-01.patch

Test added in HDFS-11708 detected this issue. So no more test has been added.
If the source changes removed then test will timeout (actually takes more than 40 seconds
to complete), but finally read will succeed if there was no timeout.

Current patch includes both HDFS-11708 and HDFS-11738 changes as HDFS-11708 is not committed
yet.

> 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
>
>
> 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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