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https://issues.apache.org/jira/browse/HDFS-9924?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15328931#comment-15328931
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Arpit Agarwal commented on HDFS-9924:
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Hi [~andrew.wang], the discussion has diverged from the merits of the API to
branching.
A feature branch is not an end goal in itself - it should aid feature
development. We have generally used feature branches to avoid destabilizing
release branches and that doesn't appear to be a risk here. So branching just
defers the API discussion to branch merge time.
Moving on to the merits of CompletableFuture vs Future - everyone seems to
agree that CompletableFuture is a good choice for 3.x which addresses your
original concerns. Everyone also agrees that CompletableFuture is obviously out
for 2.x and Guava's ListenableFuture is a bad idea. The remaining point of
disagreement appears to be whether we should expose a Future-based API for 2.x
or do nothing. Since some downstream developers have expressed an interest in
trying out a 2.x Future-based API even if it's tagged as Unstable/Experimental,
is there a compelling reason to deny it? If Future turns to be of no use to
anyone we can evolve the API in a later 2.x release or just revert it
completely while the way forward (3.x) remains unaffected.
> [umbrella] Asynchronous HDFS Access
> -----------------------------------
>
> Key: HDFS-9924
> URL: https://issues.apache.org/jira/browse/HDFS-9924
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: fs
> Reporter: Tsz Wo Nicholas Sze
> Assignee: Xiaobing Zhou
> Attachments: AsyncHdfs20160510.pdf
>
>
> This is an umbrella JIRA for supporting Asynchronous HDFS Access.
> Currently, all the API methods are blocking calls -- the caller is blocked
> until the method returns. It is very slow if a client makes a large number
> of independent calls in a single thread since each call has to wait until the
> previous call is finished. It is inefficient if a client needs to create a
> large number of threads to invoke the calls.
> We propose adding a new API to support asynchronous calls, i.e. the caller is
> not blocked. The methods in the new API immediately return a Java Future
> object. The return value can be obtained by the usual Future.get() method.
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