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https://issues.apache.org/jira/browse/HDFS-1907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13043184#comment-13043184
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John George commented on HDFS-1907:
-----------------------------------
{noformat}
assert curOff >= blk.getStartOffset() : "Block not found";
{noformat}
The only way that (I can think of) where this assert is hit is if bytesRead
becomes negative and/or a wrong block is returned.
{noformat}
TODO? Assert if the read request exceeds the length of the unfinalized +
finalized blocks.
{noformat}
Sorry but I do not get the point of this TODO? I do not see how it brings
consistency. Can you elaborate a little more? And I am little lost as to why
both the asserts are related.
> 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
> 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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