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https://issues.apache.org/jira/browse/HDFS-9924?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15293809#comment-15293809
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Colin Patrick McCabe commented on HDFS-9924:
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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 sense.
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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