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https://issues.apache.org/jira/browse/HDFS-14067?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16685910#comment-16685910
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Chao Sun commented on HDFS-14067:
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[~zero45] observer state is not currently an extension of standby, instead it
is a separate state in {{HAServiceProtocol}}, which is used by failover
mechanism. Regarding the "double promotion", I think the original design is to
favor standby over observer in failover. Otherwise, we may get unexpected
behavior from the system (e.g., the only observer gets transitioned into
active, and all traffic now goes to it). In this case, the failover controller
will need to recognize the observer state as well, which complicates things.
[~xkrogen] yes agree. I also think we should start to look into HDFS-13182
soon.
> Allow manual failover between standby and observer
> --------------------------------------------------
>
> Key: HDFS-14067
> URL: https://issues.apache.org/jira/browse/HDFS-14067
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Chao Sun
> Assignee: Chao Sun
> Priority: Major
> Attachments: HDFS-14067-HDFS-12943.000.patch
>
>
> Currently if automatic failover is enabled in a HA environment, transition
> from standby to observer would be blocked:
> {code}
> [hdfs@*** hadoop-3.3.0-SNAPSHOT]$ bin/hdfs haadmin -transitionToObserver ha2
> Automatic failover is enabled for NameNode at ****
> Refusing to manually manage HA state, since it may cause
> a split-brain scenario or other incorrect state.
> If you are very sure you know what you are doing, please
> specify the --forcemanual flag.
> {code}
> We should allow manual transition between standby and observer in this case.
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