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https://issues.apache.org/jira/browse/HDFS-14624?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16879440#comment-16879440
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Íñigo Goiri commented on HDFS-14624:
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+1 on [^HDFS-14624.002.patch].
> When decommissioning a node, log remaining blocks to replicate periodically
> ---------------------------------------------------------------------------
>
> Key: HDFS-14624
> URL: https://issues.apache.org/jira/browse/HDFS-14624
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 3.3.0
> Reporter: Stephen O'Donnell
> Assignee: Stephen O'Donnell
> Priority: Major
> Attachments: HDFS-14624.001.patch, HDFS-14624.002.patch
>
>
> When a node is marked for decommission, there is a monitor thread which runs
> every 30 seconds by default, and checks if the node still has pending blocks
> to be replicated before the node can complete replication.
> There are two existing debug level messages logged in the monitor thread,
> DatanodeAdminManager$Monitor.check(), which log the correct information
> already, first as the pending blocks are replicated:
> {code:java}
> LOG.debug("Node {} still has {} blocks to replicate "
> + "before it is a candidate to finish {}.",
> dn, blocks.size(), dn.getAdminState());{code}
> And then after the initial set of blocks has completed and a rescan happens:
> {code:java}
> LOG.debug("Node {} {} healthy."
> + " It needs to replicate {} more blocks."
> + " {} is still in progress.", dn,
> isHealthy ? "is": "isn't", blocks.size(), dn.getAdminState());{code}
> I would like to propose moving these messages to INFO level so it is easier
> to monitor decommission progress over time from the Namenode log.
> Based on the default settings, this would result in at most 1 log message per
> node being decommissioned every 30 seconds. The reason this is at the most,
> is because the monitor thread stops after checking after 500K blocks and
> therefore in practice it could be as little as 1 log message per 30 seconds,
> even if many DNs are being decommissioned at the same time.
> Note that the namenode webUI does display the above information, but having
> this in the NN logs would allow progress to be tracked more easily.
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