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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