[jira] [Created] (HDFS-7990) IBR delete ack should not be delayed

["Daryn Sharp (JIRA)" <ji...@apache.org>]

Daryn Sharp created HDFS-7990:
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             Summary: IBR delete ack should not be delayed
                 Key: HDFS-7990
                 URL: https://issues.apache.org/jira/browse/HDFS-7990
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: namenode
    Affects Versions: 2.0.0-alpha
            Reporter: Daryn Sharp
            Assignee: Daryn Sharp


HDFS-395 added the incremental BR feature.  A concern was avoiding a race condition with ack-ing block invalidates followed by the directory scanner re-adding the block before the async delete service removes the block, possibly resulting in a full BR that includes the previously delete ack-ed block.

The solution was to batch & delay block deletion acks via a hardcoded interval of 100 * heartbeat interval (default: 5min).  The delay isn't required:
#  The {{FSDatasetSpi}} tracks blocks pending deletions precisely so the scanner won't re-add the block to the volume map
# Block receiving, received, and deleted go into the same pending report.  A block received event will trigger an immediate IBR which includes the deletion acks.  Ie. The delay is meaningless for all but a quiescent cluster
# Failing to promptly report deleted blocks on a quiescent cluster prevents the NN from updating the block maps to remove the locations



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