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https://issues.apache.org/jira/browse/HADOOP-9371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13602166#comment-13602166
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Steve Loughran commented on HADOOP-9371:
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[~mikelid] all good points.
How about you submit a patch to the md file for the implicit assumptions, the
copy-paste and the root dir -that one being easy to test on all but localfs.
That "what happens to read during a write or append" is a tough one. HDFS
silently serves up new data when the read crosses a block, which I'm not
convinced is what anyone expects to have happen.
We could rephrase consistency "after any update operation has completed, read
operations initiated afterwards see a consistent view of the latest data"?
Even there, the ambiguity of what happens of read-during-write is something we
should pull out, as it may be where user expectations != hdfs operation
> Define Semantics of FileSystem and FileContext more rigorously
> --------------------------------------------------------------
>
> Key: HADOOP-9371
> URL: https://issues.apache.org/jira/browse/HADOOP-9371
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs
> Affects Versions: 1.2.0, 3.0.0
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Attachments: HADOOP-9361.patch, HadoopFilesystemContract.pdf
>
> Original Estimate: 48h
> Remaining Estimate: 48h
>
> The semantics of {{FileSystem}} and {{FileContext}} are not completely
> defined in terms of
> # core expectations of a filesystem
> # consistency requirements.
> # concurrency requirements.
> # minimum scale limits
> Furthermore, methods are not defined strictly enough in terms of their
> outcomes and failure modes.
> The requirements and method semantics should be defined more strictly.
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