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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9924) [umbrella] Asynchronous HDFS Access
Date Thu, 09 Jun 2016 23:39:21 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9924?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15323603#comment-15323603
] 

Andrew Wang commented on HDFS-9924:
-----------------------------------

[~vgumashta] and [~ashutoshc] thanks for joining the discussion. Since we have you here, could
you comment on the alternative of using a threadpool for this usecase in Hive? It seems far
more maintainable than us committing a private API you'd need to hardcode against, especially
an API that we are already planning to change. Threads in Java are pretty cheap, and the calls
are likely network/NN bound anyway.

Our other downstream users are pushing for a callback API, so if the Future-based API is solving
a problem unique to Hive, I'm curious what was already tried on the Hive side. Even if a threadpool
is less optimal, it might tide you over until the callback API is ready (which would make
everyone happy).

> [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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