Tsz Wo (Nicholas), SZE created HDFS-5285:
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Summary: Flatten INodeFile hierarchy
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: Tsz Wo (Nicholas), SZE
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.
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