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https://issues.apache.org/jira/browse/HDFS-8999?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15118581#comment-15118581
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Tsz Wo Nicholas Sze commented on HDFS-8999:
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> ... then change DN to send IBRs in batches in another JIRA.
Filed HDFS-9710.
> Namenode need not wait for {{blockReceived}} for the last block before
> completing a file.
> -----------------------------------------------------------------------------------------
>
> Key: HDFS-8999
> URL: https://issues.apache.org/jira/browse/HDFS-8999
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Reporter: Jitendra Nath Pandey
> Assignee: Tsz Wo Nicholas Sze
> Attachments: h8999_20151228.patch, h8999_20160106.patch,
> h8999_20160106b.patch, h8999_20160106c.patch, h8999_20160111.patch,
> h8999_20160113.patch, h8999_20160114.patch, h8999_20160121.patch,
> h8999_20160121b.patch, h8999_20160121c.patch, h8999_20160121c_branch-2.patch
>
>
> This comes out of a discussion in HDFS-8763. Pasting [~jingzhao]'s comment
> from the jira:
> {quote}
> ...whether we need to let NameNode wait for all the block_received msgs to
> announce the replica is safe. Looking into the code, now we have
> # NameNode knows the DataNodes involved when initially setting up the
> writing pipeline
> # If any DataNode fails during the writing, client bumps the GS and
> finally reports all the DataNodes included in the new pipeline to NameNode
> through the updatePipeline RPC.
> # When the client received the ack for the last packet of the block (and
> before the client tries to close the file on NameNode), the replica has been
> finalized in all the DataNodes.
> Then in this case, when NameNode receives the close request from the client,
> the NameNode already knows the latest replicas for the block. Currently the
> checkReplication call only counts in all the replicas that NN has already
> received the block_received msg, but based on the above #2 and #3, it may be
> safe to also count in all the replicas in the
> BlockUnderConstructionFeature#replicas?
> {quote}
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