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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-928) make checksums optional per FileSystem
Date Wed, 21 Feb 2007 22:56:05 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12474865
] 

Hairong Kuang commented on HADOOP-928:
--------------------------------------

How about the following proposal to remove FSInputStream?

1. Replace current FSInputStream with FSDataInputStream.
  * FSDataInputStream extends DataInputStream and implemets Seekable and PositionedReadable.
  * Every file system including ChecksumedFileSystem provides its own specific implementation
of FSDataInputStream.
  * Open returns a FSDataInputStream.
2. Replace current FSDataInputStream with BufferedFSDataInputStream.
  * BufferedFSDataInputStream extends FSDataInputStream, providing a buffered and position
cached implementation of FSDataInputStream.
  * Open(file, buffersize) returns a BufferedFSDataInputStream.

> 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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