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https://issues.apache.org/jira/browse/HDFS-17231?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Xiaoqiao He reassigned HDFS-17231:
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Assignee: kuper
> HA: Safemode should exit when resources are from low to available
> -----------------------------------------------------------------
>
> Key: HDFS-17231
> URL: https://issues.apache.org/jira/browse/HDFS-17231
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: ha
> Affects Versions: 3.3.4, 3.3.6
> Reporter: kuper
> Assignee: kuper
> Priority: Major
> Labels: pull-request-available
> Attachments: 企业微信截图_75d15d37-26b7-4d88-ac0c-8d77e358761b.png
>
>
> The NameNodeResourceMonitor automatically enters safe mode when it detects
> that the resources are not sufficient. When zkfc detects insufficient
> resources, it triggers failover. Consider the following scenario:
> * Initially, nn01 is active and nn02 is standby. Due to insufficient
> resources in dfs.namenode.name.dir, the NameNodeResourceMonitor detects the
> resource issue and puts nn01 into safemode. Subsequently, zkfc triggers
> failover.
> * At this point, nn01 is in safemode (ON) and standby, while nn02 is in
> safemode (OFF) and active.
> * After a period of time, the resources in nn01's dfs.namenode.name.dir
> recover, causing a slight instability and triggering failover again.
> * Now, nn01 is in safe mode (ON) and active, while nn02 is in safe mode
> (OFF) and standby.
> * However, since nn01 is active but in safemode (ON), hdfs cannot be read
> from or written to.
> !企业微信截图_75d15d37-26b7-4d88-ac0c-8d77e358761b.png!
> *reproduction*
> # Increase the dfs.namenode.resource.du.reserved
> # Increase the ha.health-monitor.check-interval.ms can avoid directly
> switching to standby and stopping the NameNodeResourceMonitor thread.
> Instead, it is necessary to wait for the NameNodeResourceMonitor to enter
> safe mode before switching to standby.
> # On the nn01 active node, using the dd command to create a file that
> exceeds the threshold, triggering a low on available disk space condition.
> # If the nn01 namenode process is not dead, the situation of nn01 safemode
> (ON) and standby occurs.
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