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https://issues.apache.org/jira/browse/HDFS-11828?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Virajith Jalaparti updated HDFS-11828:
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Summary: [WRITE] Refactor FsDatasetImpl to use the BlockAlias from
ClientProtocol for PROVIDED blocks. (was: [READ] Refactor FsDatasetImpl to use
the BlockAlias from ClientProtocol for PROVIDED blocks.)
> [WRITE] Refactor FsDatasetImpl to use the BlockAlias from ClientProtocol for
> PROVIDED blocks.
> ---------------------------------------------------------------------------------------------
>
> Key: HDFS-11828
> URL: https://issues.apache.org/jira/browse/HDFS-11828
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Ewan Higgs
> Assignee: Ewan Higgs
>
> From HDFS-11639:
> {quote}[~virajith]
> Looking over this patch, one thing that occurred to me is if it makes sense
> to unify FileRegionProvider with BlockProvider? They both have very close
> functionality.
> I like the use of BlockProvider#resolve(). If we unify FileRegionProvider
> with BlockProvider, then resolve can return null if the block map is
> accessible from the Datanodes also. If it is accessible only from the
> Namenode, then a non-null value can be propagated to the Datanode.
> One of the motivations for adding the BlockAlias to the client protocol was
> to have the blocks map only on the Namenode. In this scenario, the ReplicaMap
> in FsDatasetImpl of will not have any replicas apriori. Thus, one way to
> ensure that the FsDatasetImpl interface continues to function as today is to
> create a FinalizedProvidedReplica in FsDatasetImpl#getBlockInputStream when
> BlockAlias is not null.
> {quote}
> {quote}[~ehiggs]
> With the pending refactoring of the FsDatasetImpl which won't have replicas a
> priori, I wonder if it makes sense for the Datanode to have a
> FileRegionProvider or BlockProvider at all. They are given the appropriate
> block ID and block alias in the readBlock or writeBlock message. Maybe I'm
> overlooking what's still being provided.{quote}
> {quote}[~virajith]
> I was trying to reconcile the existing design (FsDatasetImpl knows about
> provided blocks apriori) with the new design where FsDatasetImpl will not
> know about these before but just constructs them on-the-fly using the
> BlockAlias from readBlock or writeBlock. Using BlockProvider#resolve() allows
> us to have both designs exist in parallel. I was wondering if we should still
> retain the earlier given the latter design.
> {quote}
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