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From "Vinayakumar B (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HDFS-11708) positional read will fail if replicas moved to different DNs after stream is opened
Date Sun, 28 May 2017 09:58:04 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11708?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16027764#comment-16027764
] 

Vinayakumar B edited comment on HDFS-11708 at 5/28/17 9:57 AM:
---------------------------------------------------------------

Attached the patch for the update.

1. Reason for test's failure to detect issue during full run is HDFS-11898. {{TestPread#testPreadFailureWithChangedBlockLocations()}}
was also using hedged reads, for which issue will not occur. Included those changes as well
here for jenkins run.
2.
bq. It seems like a rather fancy way to update a block variable that got stale. Would've preferred
something more explicit
Using the return value of {{choseDatanode()}} to return the updated {{block}} as well. So
avoiding the redundant calls to {{refreshLocatedBlock()}};

Please give your thoughts.


was (Author: vinayrpet):
Attached the patch for the update.

1. Reason for test's failure to detect issue during full run is HDFS-11898. Included those
changes as well here for jenkins run.
2.
bq. It seems like a rather fancy way to update a block variable that got stale. Would've preferred
something more explicit
Using the return value of {{choseDatanode()}} to return the updated {{block}} as well. So
avoiding the redundant calls to {{refreshLocatedBlock()}};

Please give your thoughts.

> positional read will fail if replicas moved to different DNs after stream is opened
> -----------------------------------------------------------------------------------
>
>                 Key: HDFS-11708
>                 URL: https://issues.apache.org/jira/browse/HDFS-11708
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs-client
>    Affects Versions: 2.7.3
>            Reporter: Vinayakumar B
>            Assignee: Vinayakumar B
>            Priority: Critical
>              Labels: release-blocker
>         Attachments: HDFS-11708-01.patch, HDFS-11708-02.patch, HDFS-11708-03.patch, HDFS-11708-04.patch,
HDFS-11708-05.patch, HDFS-11708-HDFS-11898-06.patch
>
>
> Scenario:
> 1. File was written to DN1, DN2 with RF=2
> 2. File stream opened to read and kept. Block Locations are [DN1,DN2]
> 3. One of the replica (DN2) moved to another datanode (DN3) due to datanode dead/balancing/etc.
> 4. Latest block locations in NameNode will be DN1 and DN3 in the 'same order'
> 5. DN1 went down, but not yet detected as dead in NameNode.
> 6. Client start reading using positional read api "read(pos, buf[], offset, length)"



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