FTP/FTPS/SFTP filesystem module

["Waldmann, Lukas" <lu...@merck.com>]

Hi fellow developer,
I would like to ask you for a review and testing of a new module which I hope will replace current implementation of FTP filesystem.
Patch is available here: https://issues.apache.org/jira/browse/HADOOP-14444
Benefits of new module:
* Support for FTP, FTPS and SFTP protocols
* Support for HTTP/SOCKS proxies
* Support for passive FTP
* Support for explicit FTPS
* 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 particular files across whole directory tree
* Support for reestablishing broken ftp data transfers - can happen surprisingly often

Thank you for your cooperation

Lukas

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