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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5285) Flatten INodeFile hierarchy: Add UnderContruction Feature
Date Fri, 14 Feb 2014 06:52:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5285?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13901162#comment-13901162
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Tsz Wo (Nicholas), SZE commented on HDFS-5285:
----------------------------------------------

+1 the branch-2 patch looks good.

> Flatten INodeFile hierarchy: Add UnderContruction Feature
> ---------------------------------------------------------
>
>                 Key: HDFS-5285
>                 URL: https://issues.apache.org/jira/browse/HDFS-5285
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: namenode
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Jing Zhao
>             Fix For: 3.0.0
>
>         Attachments: HDFS-5285.001.patch, HDFS-5285.002.patch, HDFS-5285.003.patch, HDFS-5285.b2.patch,
h5285_20131001.patch, h5285_20131002.patch, h5285_20131118.patch
>
>
> For files, there are INodeFile, INodeFileUnderConstruction, INodeFileWithSnapshot and
INodeFileUnderConstructionWithSnapshot for representing whether a file is under construction
or whether it is in some snapshot.  The following are two major problems of the current approach:
> - Java class does not support multiple inheritances so that INodeFileUnderConstructionWithSnapshot
cannot extend both INodeFileUnderConstruction and INodeFileWithSnapshot.
> - The number of classes is exponential to the number of features.  Currently, there are
only two features, UnderConstruction and WithSnapshot.  The number of classes is 2^2 = 4.
 It is hard to add one more feature since the number of classes will become 2^3 = 8.
> As a first step, we implement an Under-Construction feature to replace INodeFileUnderConstruction
and INodeFileUnderConstructionWithSnapshot in this jira.



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