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https://issues.apache.org/jira/browse/HDFS-5285?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13829557#comment-13829557
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Vinay commented on HDFS-5285:
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+1, patch looks good Jing.
> 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, 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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