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From "Xiaowei Zhu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-10796) libhdfs++: rationalize ioservice interactions
Date Fri, 09 Dec 2016 21:20:59 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10796?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15736377#comment-15736377
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Xiaowei Zhu commented on HDFS-10796:
------------------------------------

Things look good to me. The only concern is the failures with multiply threads running. I
think one way to verify that this patch doesn't introduce anything new is to only set number
o threads larger than 1 and run the tests. Then we can compare w/ and w/o your patch, if the
failures look all the same, and if there is anything new.

> libhdfs++: rationalize ioservice interactions
> ---------------------------------------------
>
>                 Key: HDFS-10796
>                 URL: https://issues.apache.org/jira/browse/HDFS-10796
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: hdfs-client
>            Reporter: Bob Hansen
>            Assignee: James Clampffer
>         Attachments: HDFS-10796.HDFS-8707.000.patch
>
>
> Firstly, we should be pulling the number of threads from options.io_threads (which should
default to std::thread::hardware_concurrency()).  The library should pass all tests always
with io_threads set to 1 or to <a very high number>
> Secondly, we should have _a_ constructor where the consumer doesn't need to manage the
IOService explicitly, and the FileSystemImpl should create its own internally.
> Since the FileSystem is defined as being for a particular user/identity, there is a valid
use case for the consumer to be constructing many FileSystem instances to represent many authenticated
users in the same process, but want to share resources (notably have a single io_service shared
amongst them all).  In this case, the consumer would want to own the IOService and pass the
same instance to multiple FileSystem instances.



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