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https://issues.apache.org/jira/browse/HDFS-6803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14089546#comment-14089546
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stack commented on HDFS-6803:
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[~cmccabe] Thanks for the very nice feedback. Let me incorporate/fix what has
been posted.
[[email protected]] Thanks for jumping on boss.
bq. Consistency with actual file data & metadata....
Yes. Lets fold in your text. You are describing the FS as it is today.
bq. ...The second read() would succeed/return -1 depending on the position
Do you mean the third read in above?
bq. When a pread is in progress, should that change be visible in getPos()?
I like [~cmccabe]'s groupings which implies pread does not change getPos.
How should I proceed with this issue [[email protected]]? I'd like to get 2.1
and 2.2 (from attached doc) blessed as scripture. Seems like a bit of cleanup
is all that is needed in HDFS (and as [~hitliuyi] suggests, we could probably
remove some synchronizes). My guess is the other FS implementations have not
been implemented the way HDFS has been and that backfilling a pread to run
independent of a read would be a bunch of work. Would this work be a blocker
on adding 2.1/2.2 to the spec and HDFS? Thanks Steve.
> Documenting DFSClient#DFSInputStream expectations reading and preading in
> concurrent context
> --------------------------------------------------------------------------------------------
>
> Key: HDFS-6803
> URL: https://issues.apache.org/jira/browse/HDFS-6803
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs-client
> Affects Versions: 2.4.1
> Reporter: stack
> Attachments: DocumentingDFSClientDFSInputStream (1).pdf
>
>
> Reviews of the patch posted the parent task suggest that we be more explicit
> about how DFSIS is expected to behave when being read by contending threads.
> It is also suggested that presumptions made internally be made explicit
> documenting expectations.
> Before we put up a patch we've made a document of assertions we'd like to
> make into tenets of DFSInputSteam. If agreement, we'll attach to this issue
> a patch that weaves the assumptions into DFSIS as javadoc and class comments.
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