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https://issues.apache.org/jira/browse/HDFS-8999?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15084414#comment-15084414
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Jing Zhao commented on HDFS-8999:
---------------------------------

Another question is whether we should update the new logic from HDFS-1172 and 
HDFS-9535. In HDFS-1172, we add the replica to the pending queue only when 
there are already >=1 live replicas. Now since the client can close the file 
without waiting for the IBR, we will add the block into the UnderReplicated 
queue with {{QUEUE_WITH_CORRUPT_BLOCKS}} priority. I think maybe we should 
still put the block into the pending queue in this scenario.

> 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
>
>
> 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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