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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9924) [umbrella] Asynchronous HDFS Access
Date Fri, 20 May 2016 17:37:13 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9924?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15293809#comment-15293809

Colin Patrick McCabe commented on HDFS-9924:

I have to agree with [~andrew.wang] that it makes more sense to put these changes in trunk
than in branch-2.  The Hadoop 2.8 release has been blocked for a very, very long time.  There
are tons of features in branch-2 that have been waiting for almost a year to be released.
 Adding yet another feature to branch-2, when we're so far behind on releases, doesn't make

Programmers who are familiar with Node.js will want something that supports callback chaining,
like CompletableFuture, rather than something like the old-style Future API.  If we target
this at branch-3, we can use the jdk8 CompletableFuture.

If we are going to backport this to branch-2, we should do it once the feature is done, rather
than backporting bits and pieces as we go.  This is especially true when there are still open
questions about the API.

> [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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