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https://issues.apache.org/jira/browse/HDFS-15634?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated HDFS-15634:
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    Labels: pull-request-available  (was: )

> 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
>              Labels: pull-request-available
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> 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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