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https://issues.apache.org/jira/browse/HDFS-6581?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14106069#comment-14106069
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Colin Patrick McCabe commented on HDFS-6581:
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bq. If you truncate() a file while a reader has it mmapped, will the reader get
0s or a bus error? I seem to recall it's the latter, which may be a bit nasty
for a revocation path.
A reader which reads via read() will get EOF. A reader reading via mmap will
get SIGBUS. It's not nasty, because we only do this after telling the client
to stop reading using the mechanism in HDFS-5182. The client only ever has
problems if it goes rogue and decides to ignore our message telling it to stop
reading.
> Write to single replica in memory
> ---------------------------------
>
> Key: HDFS-6581
> URL: https://issues.apache.org/jira/browse/HDFS-6581
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Reporter: Arpit Agarwal
> Assignee: Arpit Agarwal
> Attachments: HDFSWriteableReplicasInMemory.pdf
>
>
> Per discussion with the community on HDFS-5851, we will implement writing to
> a single replica in DN memory via DataTransferProtocol.
> This avoids some of the issues with short-circuit writes, which we can
> revisit at a later time.
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