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From "Lukas Waldmann (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-14444) New implementation of ftp and sftp filesystems
Date Wed, 31 May 2017 09:27:04 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-14444?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16030887#comment-16030887
] 

Lukas Waldmann commented on HADOOP-14444:
-----------------------------------------

Sure, if you environment displays often file changes than the cache should be obviously disabled.
Unfortunately you won't get any notifications from ftp/sftp that file has been changed and
you should update the cache :( Cache implemented there is the best effort and can in most
cases handle change of file size, but won't handle if a new file was created. In such scenario
it should be disabled.





> New implementation of ftp and sftp filesystems
> ----------------------------------------------
>
>                 Key: HADOOP-14444
>                 URL: https://issues.apache.org/jira/browse/HADOOP-14444
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: fs
>    Affects Versions: 2.8.0
>            Reporter: Lukas Waldmann
>            Assignee: Lukas Waldmann
>         Attachments: HADOOP-14444.patch
>
>
> Current implementation of FTP and SFTP filesystems have severe limitations and performance
issues when dealing with high number of files. Mine patch solve those issues and integrate
both filesystems such a way that most of the core functionality is common for both and therefore
simplifying the maintainability.
> The core features:
> * Support for HTTP/SOCKS proxies
> * Support for passive FTP
> * Support of connection pooling - new connection is not created for every single command
but reused from the pool.
> For huge number of files it shows order of magnitude performance improvement over not
pooled connections.
> * Caching of directory trees. For ftp you always need to list whole directory whenever
you ask information about particular file.
> Again for huge number of files it shows order of magnitude performance improvement over
not cached connections.
> * Support of keep alive (NOOP) messages to avoid connection drops
> * Support for Unix style or regexp wildcard glob - useful for listing a particular files
across whole directory tree
> * Support for reestablishing broken ftp data transfers - can happen surprisingly often



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