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https://issues.apache.org/jira/browse/HDFS-16261?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17456729#comment-17456729
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Bryan Beaudreault commented on HDFS-16261:
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I would love to get a review here if someone has time. This PR has been
deployed to more than 100 active production namenodes (plus standby similar
namenodes), serving clusters of 100s of nodes and 100's of thousands of blocks.
Has been working great for us.
> Configurable grace period around invalidation of replaced blocks
> ----------------------------------------------------------------
>
> Key: HDFS-16261
> URL: https://issues.apache.org/jira/browse/HDFS-16261
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Bryan Beaudreault
> Assignee: Bryan Beaudreault
> Priority: Major
> Labels: pull-request-available
> Time Spent: 20m
> Remaining Estimate: 0h
>
> When a block is moved with REPLACE_BLOCK, the new location is recorded in the
> NameNode and the NameNode instructs the old host to in invalidate the block
> using DNA_INVALIDATE. As it stands today, this invalidation is async but
> tends to happen relatively quickly.
> I'm working on a feature for HBase which enables efficient healing of
> locality through Balancer-style low level block moves (HBASE-26250). One
> issue is that HBase tends to keep open long running DFSInputStreams and
> moving blocks from under them causes lots of warns in the RegionServer and
> increases long tail latencies due to the necessary retries in the DFSClient.
> One way I'd like to fix this is to provide a configurable grace period on
> async invalidations. This would give the DFSClient enough time to refresh
> block locations before hitting any errors.
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