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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-928) make checksums optional per FileSystem
Date Tue, 13 Feb 2007 01:22:05 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12472494
] 

Doug Cutting commented on HADOOP-928:
-------------------------------------

Overall this looks great.  A few minor issues that I see so far are:

I think we should add an abstract FilterFileSystem, that wraps a FileSystem and delegates
all methods to the wrapped FileSystem.  This can be used by ChecksumFileSystem and PhasedFileSystem,
making these classes a lot more readable.

FileSystem.pathToFile() should check that the uri starts with 'file://', and perhaps be a
LocalFileSystem method.  As it stands, it will return a File for an HDFS path, which makes
no sense.

Do we still need FSInputStream and FSOutputStream for anything?  Or can these be removed?

This patch indents four spaces per level, rather than the preferred two.

> make checksums optional per FileSystem
> --------------------------------------
>
>                 Key: HADOOP-928
>                 URL: https://issues.apache.org/jira/browse/HADOOP-928
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: fs
>            Reporter: Doug Cutting
>         Assigned To: Hairong Kuang
>         Attachments: checksum.patch
>
>
> Checksumming is currently built into the base FileSystem class.  It should instead be
optional, with each FileSystem implementation electing whether to use the Hadoop-provided
checksum system, or to disable it, or to implement its own custom checksum system.
> To implement this, a ChecksumFileSystem implementation can be provided that wraps another
FileSystem implementation, implementing checksums as in Hadoop's current mandatory implementation
(i.e., as a separate crc file per file that's elided from directory listings).  The 'raw'
FileSystem methods would be removed.  FSDataInputStream and FSDataOutputStream would be made
interfaces.

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