[jira] [Created] (HDFS-12589) [DISCUSS] Provided Storage BlockAlias Refactoring

["Ewan Higgs (JIRA)" <ji...@apache.org>]

Ewan Higgs created HDFS-12589:
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             Summary: [DISCUSS] Provided Storage BlockAlias Refactoring
                 Key: HDFS-12589
                 URL: https://issues.apache.org/jira/browse/HDFS-12589
             Project: Hadoop HDFS
          Issue Type: Sub-task
          Components: hdfs
            Reporter: Ewan Higgs
            Priority: Minor


A BlockAlias is an interface used by the Datanode to determine where to retrieve data from. It currently has a single implementation: {{FileRegion}} which contains the Block, BlockPoolID, Provided URL for the FileRegion (i.e. block); and length and offset of the FileRegion in the remote storage.

The BlockAlias currently has a single method: {{getBlock}}. This is not particularly useful since we can't ask it meaningful questions like 'how do we retrieve the data from the external storage system?'. Or 'is the version of the block in the external storage system up to data?'. Either we can do away with the BlockAlias altogether and work with FileRegion, or the BlockAlias needs to be made more robust.



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