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From "Tsz Wo Nicholas Sze (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9924) [umbrella] Asynchronous HDFS Access
Date Mon, 13 Jun 2016 23:47:57 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9924?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15328642#comment-15328642
] 

Tsz Wo Nicholas Sze commented on HDFS-9924:
-------------------------------------------

> If there are no further comments by EOD tomorrow, I'd like to go ahead and move the commits
to the feature branch.

Please don't move anything to the feature branch.  We are still discussing it.  There are
different opinions.  Again, if we need a feature branch, the branch should be for HADOOP-12910
but not this JIRA.

> A threadpool is just a few extra MBs of memory.

It depends on how many threads in the pool.  It could be GBs of memory.  You may try Colin's
code above in his comment on creating 20,000 threads to see if it is a few extra MBs of memory.

> [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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