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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-7990) IBR delete ack should not be delayed
Date Wed, 25 Mar 2015 22:09:52 GMT
Daryn Sharp created HDFS-7990:

             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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