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From "Jitendra Nath Pandey (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-8999) Namenode need not wait for {{blockReceived}} for the last block before completing a file.
Date Tue, 01 Sep 2015 17:22:45 GMT
Jitendra Nath Pandey created HDFS-8999:

             Summary: 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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