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https://issues.apache.org/jira/browse/HDDS-4342?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aravindan Vijayan resolved HDDS-4342.
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Resolution: Fixed
Merged the PR.
> Add DataNode state and transitions for a node going through upgrade
> -------------------------------------------------------------------
>
> Key: HDDS-4342
> URL: https://issues.apache.org/jira/browse/HDDS-4342
> Project: Hadoop Distributed Data Store
> Issue Type: Sub-task
> Reporter: Prashant Pogde
> Assignee: Prashant Pogde
> Priority: Major
> Labels: pull-request-available
>
> A typical SCM sequence for driving datanodes through upgrade would be
> Something like following :
>
> - client sends Finalize
>
> - SCM moves to Finalizing states. If SCM crashes, and it comes up
>
> it will always restart from this state.
>
> - SCM disallows new pipeline creation, SCM in safe mode
>
> (SCM Freeze for new pipeline)
>
> - SCM closes existing pieplines
>
> - SCM updates MLV = SLV if not already so. Update on-disk MLV state.
>
> - SCM moves all data nodes to HEALTHY_READONLY state. Please note that
>
> initial state for all data node is HEALTHY_READONLY. For data nodes
>
> to move from HEALTHY_READONLY -> HEALTHY, they need to send atleast
>
> one heartbeat where DN.MLV == SCM.MLV
>
> - SCM waits for few heartbeats
>
> - SCM allows new pipeline creation (SCM thaw for new pipeline creation).
>
> New Pipelines can be created if enough HEALTHY data nodes are found.
>
> - If SCM comes across any data node heart beat with DN.MLV < SCM.MLV => SCM
> sends
> that data node finalize command
> ======================================================================
>
> As part of this, we would be introducing a new state HEALTHY-READONLY in
> DataNode state machine maintained in SCM .
> This Jira will be used to make changes in the datanode state machine.
>
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