[jira] Commented: (HDFS-1473) Refactor storage management into separate classes than fsimage file reading/writing

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

    [ https://issues.apache.org/jira/browse/HDFS-1473?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12965525#action_12965525 ] 

Konstantin Shvachko commented on HDFS-1473:
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Sorry for late response. Was just looking at it on Sunday when Eli committed it, so I stopped. Now looking at it in trunk I feel it needs more work, mostly because I see lots of unnecessary public methods and classes.
# FSImageCompression should not have public methods except for toString().
# FSImageFormat should not be abstract and should not have anything public.
# FSImageSerialization should not be abstract. It does not have any abstract methods. I understand we will get rid of other public qualifiers once OIV moves inside namenode package. Could we please state it in the beginning of the class.
# FSImageFormat.Loader and FSImageFormat.Writer seem like a mismatch. Loader rhythms with saver, reader with writer. Just a teerminology issue. We used to load and save image. Now we load and write it. I'd stay with the traditional terms.
# FSImageSerialization.TL_DATA is the new name for former FSImage.FILE_PERM. I agree FILE_PERM is not the best choice, but TL_DATA lacks any meaning attributed to the object. And if it once will become a non-thread local object then the name will be completely irrelevant. I'd go with the original name and rename in a separate issue. In general, refactoring patches should avoid renaming.

> Refactor storage management into separate classes than fsimage file reading/writing
> -----------------------------------------------------------------------------------
>
>                 Key: HDFS-1473
>                 URL: https://issues.apache.org/jira/browse/HDFS-1473
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>             Fix For: 0.22.0, 0.23.0
>
>         Attachments: hdfs-1473-prelim.txt, hdfs-1473.txt, hdfs-1473.txt, hdfs-1473.txt
>
>
> Currently the FSImage class is responsible both for storage management (eg moving around files, tracking file names, the VERSION file, etc) as well as for the actual serialization and deserialization of the "fsimage" file within the storage directory.
> I'd like to refactor the loading and saving code into new classes. This will make testing easier and also make the major changes in HDFS-1073 easier to understand.

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