[jira] Commented: (HADOOP-6253) Add a Ceph FileSystem interface.

["Konstantin Shvachko (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-6253?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12764882#action_12764882 ] 

Konstantin Shvachko commented on HADOOP-6253:
---------------------------------------------

Hey Gregory, Good job!  Always wanted to compare Ceph with HDFS.
Took a quick look at your patch. Noticed there some indentation issues: we use tabs as 2 spaces.
Also there are several warnings:
# In all 3 files many imports are not necessary (like Vector, File), which is shown as warnings in eclipse.
# There is a comment line in the beginning of each file - should be removed.
# In {{CephFileSystem}} the following members and methods are not used anywhere:
    cephDebugLevel;
    monAddr;
    ceph_mkdir()
# {{bufferSize}} is not used neither in {{CephInputStream}} nor in {{CephOutputStream}}.
# {{ceph_seek_from_start()}} is unused in {{CephOutputStream}}.
# I see you explicitly throw RuntimeExceptions, like NullPointerException or IndexOutOfBoundsException, in your implementation. It would be better to replace them with IOExceptions. RuntimeExceptions should be treated as a bug in the code.

What about libhadoopceph? Is it a part of Hadoop or Ceph?
About testing. You might want to check KosmosFileSystem and S3FileSystem for testing examples. You want some tests committed with your patch because without tests software becomes stale pretty fast. In this case tests should test not the file system functionality, but your wrapping software, imho.

> Add a Ceph FileSystem interface.
> --------------------------------
>
>                 Key: HADOOP-6253
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6253
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: fs
>            Reporter: Gregory Farnum
>            Priority: Minor
>         Attachments: HADOOP-6253.patch, HADOOP-6253.patch, HADOOP-6253.patch
>
>
> The experimental distributed filesystem Ceph does not have a single point of failure, and might be of use to some Hadoop users.

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