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https://issues.apache.org/jira/browse/HDFS-6803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14095162#comment-14095162
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Yi Liu commented on HDFS-6803:
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{quote}
It seems like we are all in agreement on Stack's point 2.1 (positional read and
non-positional can run concurrently), and 2.2 (two or more positional reads can
run concurrently)
{quote}
Yes.
Should we require the implementations of {{FSInputStream}} should be
thread-safe (or at least for PositionedReadable)? And modify some
implementations such as WebHDFS to make pread concurrently?
{quote}
There's always the strategy of adding a marker interface, say
ConcurrentPositionalReads, which indicates the operations are concurrent.
{quote}
Maybe using existing PositionedReadable is OK and keep the concurrent in java
doc as what we do now?
> 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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