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Date: Tue, 14 Jun 2016 02:46:58 +0000 (UTC)
From: "Tsz Wo Nicholas Sze (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12948243.1457488146000.1967.1465872418427@Atlassian.JIRA>
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References: <JIRA.12948243.1457488146000@Atlassian.JIRA> <JIRA.12948243.1457488146818@arcas>
Subject: [jira] [Commented] (HDFS-9924) [umbrella] Asynchronous HDFS Access
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archived-at: Tue, 14 Jun 2016 02:47:00 -0000


    [ https://issues.apache.org/jira/browse/HDFS-9924?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15328835#comment-15328835 ] 

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

> I'll let Vaibhav and Ashutosh comment on the suitable number of threads for Hive. Let's just say though that the right number is far less than 20k, ...

Then, why choose 10 but not 20 or 100?  More generally, how do decide what is the number of threads to use?

> [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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