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Date: Thu, 24 Aug 2017 07:22:00 +0000 (UTC)
From: "Bernd Eckenfels (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (VFS-640) Synchronized
 AbstractOriginatingFileProvider.getFileSystem is too broad
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archived-at: Thu, 24 Aug 2017 07:22:07 -0000


    [ https://issues.apache.org/jira/browse/VFS-640?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16139696#comment-16139696 ] 

Bernd Eckenfels commented on VFS-640:
-------------------------------------

We need to be careful in case it is called recursively for layered filesystems.

> Synchronized AbstractOriginatingFileProvider.getFileSystem is too broad
> -----------------------------------------------------------------------
>
>                 Key: VFS-640
>                 URL: https://issues.apache.org/jira/browse/VFS-640
>             Project: Commons VFS
>          Issue Type: Bug
>    Affects Versions: 2.0, 2.1
>            Reporter: L
>         Attachments: ParallelConnTest.java, patch_VFS640.diff
>
>
> Currently (rev. 1802455) this method looks like this:
> {code:java}
>     protected synchronized FileSystem getFileSystem(final FileName rootName, final FileSystemOptions fileSystemOptions)
>         throws FileSystemException
>     {
>         FileSystem fs = findFileSystem(rootName, fileSystemOptions);
>         if (fs == null)
>         {
>             // Need to create the file system, and cache it
>             fs = doCreateFileSystem(rootName, fileSystemOptions);
>             addFileSystem(rootName, fs);
>         }
>         return fs;
>     }
> {code}
> Given that there is a single instance of a provider per scheme, a very slow server that is being accessed first time will block *all* other threads trying to access some other resources via the same provider.
> We have a server that takes sometimes 20-30 seconds in doCreateFileSystem. We do not mind the thread trying to access this method taking that long, but because of that "synchronized" we end up having multiple threads accessing unrelated servers for the same scheme blocked.
> PS. Actually, it is not only AbstractOriginatingFileProvider. The same "provider-scoped" lock is present in AbstractLayeredFileProvider, TemporaryFileProvider, and UrlFileProvider


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