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https://issues.apache.org/jira/browse/HDFS-1907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13042220#comment-13042220
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Daryn Sharp commented on HDFS-1907:
-----------------------------------
I'd suggest a temporary boolean for whether the read went past the end of the
finalized block. You might even consider simplifying all the logic to:
{code}
- final List<LocatedBlock> blocks;
- if (locatedBlocks.isLastBlockComplete()) {
- blocks = getFinalizedBlockRange(offset, length);
- }
- else {
- if (length + offset > locatedBlocks.getFileLength()) {
- length = locatedBlocks.getFileLength() - offset;
- }
- blocks = getFinalizedBlockRange(offset, length);
+ boolean readPastEnd = (offset + length > locatedBlocks.getFileLength());
+ if (readPastEnd) length = locatedBlocks.getFileLength() - offset;
+
+ final List<LocatedBlock> blocks = getFinalizedBlockRange(offset, length);
+ if (readPastEnd && !locatedBlocks.isLastBlockComplete()) {
blocks.add(locatedBlocks.getLastLocatedBlock());
}
{code}
> 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.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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