[
https://issues.apache.org/jira/browse/HDFS-6803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14222836#comment-14222836
]
Steve Loughran commented on HDFS-6803:
--------------------------------------
sorry, been at apachecon and neglecting that jira-list.
+1 from me
ps
bq. Would it be better marking those fs that do NOT support
ConcurrentPositionalReads? (Probably not – too much work).
I think ultimately we may want to make the contract XML files describing
filesystems more visible, so you can see whether an FS is case sensitive,
raises EOF on out of bound seeks, etc. But having all that information would
only complicate code, wouldn't it? you don't want to start looking for the
specific features of the FS you are working with. Simpler to say "assume it is
HDFS or something which acts like it" and be done.
I am planning to add a {{Blobstore}} tag to object stores though, to highlight
they may be way off what HDFS offers, especially in a consistency model (which
would then be listed per-instance to let callers understand what's going to be
unreliable)
> 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: 9117.md.txt, DocumentingDFSClientDFSInputStream (1).pdf,
> DocumentingDFSClientDFSInputStream.v2.pdf, HDFS-6803v2.txt, HDFS-6803v3.txt,
> fsdatainputstream.md.v3.html
>
>
> 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.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
