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https://issues.apache.org/jira/browse/HDFS-15634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17214965#comment-17214965
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Íñigo Goiri commented on HDFS-15634:
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The proposal makes sense.
The only issue is that at the scale that this would matter, it may have some
weird side effects.
Do you have a WIP patch to see what this would look like?
> Invalidate block on decommissioning DataNode after replication
> --------------------------------------------------------------
>
> Key: HDFS-15634
> URL: https://issues.apache.org/jira/browse/HDFS-15634
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs
> Reporter: Fengnan Li
> Assignee: Fengnan Li
> Priority: Major
>
> Right now when a DataNode starts decommission, Namenode will mark it as
> decommissioning and its blocks will be replicated over to different
> DataNodes, then marked as decommissioned. These blocks are not touched since
> they are not counted as live replicas.
> Proposal: Invalidate these blocks once they are replicated and there are
> enough live replicas in the cluster.
> Reason: A recent shutdown of decommissioned datanodes to finished the flow
> caused Namenode latency spike since namenode needs to remove all of the
> blocks from its memory and this step requires holding write lock. If we have
> gradually invalidated these blocks the deletion will be much easier and
> faster.
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