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From "Chris Nauroth (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13726) Enforce that FileSystem initializes only a single instance of the requested FileSystem.
Date Thu, 13 Apr 2017 00:57:41 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13726?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15966952#comment-15966952
] 

Chris Nauroth commented on HADOOP-13726:
----------------------------------------

bq. ...maybe the {{FileSystem#initialize}} call could be moved inside a {{synchronized}} block
on the Cache.Key instance...?

No, I'm wrong about this, because it's a different {{Key}} instance on each thread, and therefore
multiple threads wouldn't be coordinating on the same lock.

> Enforce that FileSystem initializes only a single instance of the requested FileSystem.
> ---------------------------------------------------------------------------------------
>
>                 Key: HADOOP-13726
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13726
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: fs
>            Reporter: Chris Nauroth
>            Assignee: Manjunath Anand
>
> The {{FileSystem}} cache is intended to guarantee reuse of instances by multiple call
sites or multiple threads.  The current implementation does provide this guarantee, but there
is a brief race condition window during which multiple threads could perform redundant initialization.
 If the file system implementation has expensive initialization logic, then this is wasteful.
 This issue proposes to eliminate that race condition and guarantee initialization of only
a single instance.



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