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https://issues.apache.org/jira/browse/HDFS-7915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14359134#comment-14359134
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Yongjun Zhang commented on HDFS-7915:
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Hi Colin,
I realize that the {{fis}} returned by {{fis =
datanode.requestShortCircuitFdsForRead(blk, token, maxVersion);}} won't be null
if it doesn't throw exception, So please ignore my comment about
"inconsistency", but I think it'd be helpful to address the other one (include
failure reason in the log). Thanks.
> The DataNode can sometimes allocate a ShortCircuitShm slot and fail to tell
> the DFSClient about it because of a network error
> -----------------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-7915
> URL: https://issues.apache.org/jira/browse/HDFS-7915
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.7.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-7915.001.patch, HDFS-7915.002.patch
>
>
> The DataNode can sometimes allocate a ShortCircuitShm slot and fail to tell
> the DFSClient about it because of a network error. In
> {{DataXceiver#requestShortCircuitFds}}, the DataNode can succeed at the first
> part (mark the slot as used) and fail at the second part (tell the DFSClient
> what it did). The "try" block for unregistering the slot only covers a
> failure in the first part, not the second part. In this way, a divergence can
> form between the views of which slots are allocated on DFSClient and on
> server.
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