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https://issues.apache.org/jira/browse/HBASE-28376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17819253#comment-17819253
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Duo Zhang commented on HBASE-28376:
-----------------------------------
There is no such "other actions are allowed" design in our code base.
Most procedures can only be executed after master is set to initialized, except
several special procedures such as SCP and TRSP, which are carefully design to
not rely on master initialized.
For other procedures, we assume that when executing, master should have been
initialized, as it is easier for the developers to write simple and correct
code. So let the procedure could be execute before master initialized may spend
us a lot of extra effort and also make the code complicated, and easy to be
broken in the future...
> Column family ns does not exist in region during upgrade to 3.0.0-beta-2
> ------------------------------------------------------------------------
>
> Key: HBASE-28376
> URL: https://issues.apache.org/jira/browse/HBASE-28376
> Project: HBase
> Issue Type: Bug
> Components: meta
> Affects Versions: 3.0.0-beta-1
> Reporter: Bryan Beaudreault
> Assignee: Duo Zhang
> Priority: Blocker
>
> Upgrading from 2.5.x to 3.0.0-alpha-2, migrateNamespaceTable kicks in to copy
> data from the namespace table to an "ns" family of the meta table. If you
> don't have an "ns" family, the migration fails and the hmaster will crash
> loop. You then can't rollback, because the briefly alive upgraded hmaster
> created a procedure that can't be deserialized by 2.x (I don't have this log
> handy unfortunately). I tried pushing code to create the ns family on
> startup, but it doesnt work becuase the migration happens while the hmaster
> is still initializing.
> So it seems imperative that you create the ns family before upgrading. We
> should handle this more gracefully.
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