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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1907) BlockMissingException upon concurrent read and write: reader was doing file position read while writer is doing write without hflush
Date Fri, 03 Jun 2011 18:09:47 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13043924#comment-13043924
] 

Tsz Wo (Nicholas), SZE commented on HDFS-1907:
----------------------------------------------

Todd,
Oops, sorry that I did not see you comments when I was committing the patch.  Let's fix the
nits separately.

> BlockMissingException upon concurrent read and write: reader was doing file position
read while writer is doing write without hflush
> ------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1907
>                 URL: https://issues.apache.org/jira/browse/HDFS-1907
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs client
>    Affects Versions: 0.23.0
>         Environment: Run on a real cluster. Using the latest 0.23 build.
>            Reporter: CW Chung
>            Assignee: John George
>             Fix For: 0.23.0
>
>         Attachments: HDFS-1907-2.patch, HDFS-1907-3.patch, HDFS-1907-4.patch, HDFS-1907-5.patch,
HDFS-1907-5.patch, HDFS-1907.patch
>
>
> BlockMissingException is thrown under this test scenario:
> Two different processes doing concurrent file r/w: one read and the other write on the
same file
>   - writer keep doing file write
>   - reader doing position file read from beginning of the file to the visible end of
file, repeatedly
> The reader is basically doing:
>   byteRead = in.read(currentPosition, buffer, 0, byteToReadThisRound);
> where CurrentPostion=0, buffer is a byte array buffer, byteToReadThisRound = 1024*10000;
> Usually it does not fail right away. I have to read, close file, re-open the same file
a few times to create the problem. I'll pose a test program to repro this problem after I've
cleaned up a bit my current test program.

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