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https://issues.apache.org/jira/browse/HDFS-1057?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12882633#action_12882633
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Hairong Kuang commented on HDFS-1057:
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> translating a ReplicaNotFoundException into a 0-length block within
> DFSInputStream for under construction files
Should the code check all replicas before returning 0?
Ideally NN should not return block locations to readers if the block
construction is still in the pipeline construction stage.
> Concurrent readers hit ChecksumExceptions if following a writer to very end
> of file
> -----------------------------------------------------------------------------------
>
> Key: HDFS-1057
> URL: https://issues.apache.org/jira/browse/HDFS-1057
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: data-node
> Affects Versions: 0.20-append, 0.21.0, 0.22.0
> Reporter: Todd Lipcon
> Assignee: sam rash
> Priority: Blocker
> Fix For: 0.20-append
>
> Attachments: conurrent-reader-patch-1.txt,
> conurrent-reader-patch-2.txt, conurrent-reader-patch-3.txt,
> HDFS-1057-0.20-append.patch, hdfs-1057-trunk-1.txt, hdfs-1057-trunk-2.txt,
> hdfs-1057-trunk-3.txt, hdfs-1057-trunk-4.txt
>
>
> In BlockReceiver.receivePacket, it calls replicaInfo.setBytesOnDisk before
> calling flush(). Therefore, if there is a concurrent reader, it's possible to
> race here - the reader will see the new length while those bytes are still in
> the buffers of BlockReceiver. Thus the client will potentially see checksum
> errors or EOFs. Additionally, the last checksum chunk of the file is made
> accessible to readers even though it is not stable.
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