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https://issues.apache.org/jira/browse/HDFS-5589?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13839676#comment-13839676
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Andrew Wang commented on HDFS-5589:
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Perhaps related, but there's an off-by-at-least-one error here when processing
block reports. I have a 1 node cluster and added a cache directive with a repl
of 3. Saw this log message:
{noformat}
13/12/04 17:51:39 WARN blockmanagement.CacheReplicationMonitor: We need 1 more
replica(s) than actually exist to provide a cache replication of 3 for
{blockId=1073741825, replication=3, mark=false}
{noformat}
When I bumped it to 4, it said 2, and at 2 it said 0. My guess is that the
pending queue isn't getting cleared properly, leading to the single node
getting double counted.
> Namenode loops caching and uncaching when data should be uncached
> -----------------------------------------------------------------
>
> Key: HDFS-5589
> URL: https://issues.apache.org/jira/browse/HDFS-5589
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: caching, namenode
> Affects Versions: 3.0.0
> Reporter: Andrew Wang
>
> This was reported by [~cnauroth] and [~brandonli], and [~schu] repro'd it too.
> If you add a new caching directive then remove it, the Namenode will
> sometimes get stuck in a loop where it sends DNA_CACHE and then DNA_UNCACHE
> repeatedly to the datanodes where the data was previously cached.
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