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From "Vinod Kumar Vavilapalli (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-12412) Concurrency in FileSystem$Cache is very broken
Date Mon, 02 Nov 2015 21:10:27 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-12412?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vinod Kumar Vavilapalli updated HADOOP-12412:
---------------------------------------------
    Target Version/s: 2.7.3  (was: 2.7.2)

[~mharris], please see my comment above.

Moving it out of 2.7.2 per my comment above.

> Concurrency in FileSystem$Cache is very broken
> ----------------------------------------------
>
>                 Key: HADOOP-12412
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12412
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs
>    Affects Versions: 2.7.0
>            Reporter: Michael Harris
>            Assignee: Michael Harris
>            Priority: Critical
>         Attachments: HADOOP-12412.patch, HADOOP-12412.patch
>
>
> The FileSystem cache uses a mild amount of concurrency to protect the cache itself, but
does nothing to prevent multiple of the same filesystem from being constructed and initialized
simultaneously.  At best, this leads to potentially expensive wasted work.  At worst, as is
the case for Spark, it can lead to deadlocks/livelocks, especially when the same configuration
object is passed into both calls.  This should be refactored to use a results cache approach
(reference Java Concurrency in Practice chapter 5 section 6 for an example of how to do this
correctly), which will be both higher-performance and safer.



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