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https://issues.apache.org/jira/browse/HDFS-8999?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15110573#comment-15110573
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Tsz Wo Nicholas Sze commented on HDFS-8999:
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> We now have two places in completeFileInternal to add committed blocks into
> the pending queue: one is in commitOrCompleteLastBlock, and the other is
> addCommittedBlocksToPending. Do we still need the first one? Looks like we
> can now remove the changes from HDFS-1172 and HDFS-9535.
I think we still need the changes from HDFS-1172 and HDFS-9535 since they add
newly COMPLETE blocks to pending replication. The current patch adds COMMITTED
blocks to pending replication. If we remove the changes, the newly COMPLETE
blocks won't be added to pending replication.
> 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
>
>
> 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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