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https://issues.apache.org/jira/browse/HDFS-8999?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14726300#comment-14726300
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Jing Zhao commented on HDFS-8999:
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bq. if we are going to trust the client, do we even need IBRs?
Yeah, I have the same question here. [~szetszwo] once mentioned the IBR
actually could fix some data inconsistency. If we still need IBRs, can we
change its sending mechanism from block-triggering to periodical?
Also currently we trust the client on the length of the file/block. In
HDFS-8498 [~daryn] you mentioned you had seen this caused data corruption.
Could you please provide more details about the corruption so that we can
understand if we can really trust the client?
> 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
>
> This comes out of a discussion in HDFS-8763. Pasting [~jingzhao]'s comment
> from the jira:
> ...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?
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