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https://issues.apache.org/jira/browse/HBASE-20828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16533292#comment-16533292
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Duo Zhang commented on HBASE-20828:
-----------------------------------

Oh seems the above way to restore lock is still not enough, think of a 
procedure which holdLock returns true but no sub procedure, and it is in the 
middle of the execution when master restarts, we also need to restore its lock 
otherwise there maybe problem if other procedures can acquire the lock before 
it...

> Finish-up AMv2 Design/List of Tenets/Specification of operation
> ---------------------------------------------------------------
>
>                 Key: HBASE-20828
>                 URL: https://issues.apache.org/jira/browse/HBASE-20828
>             Project: HBase
>          Issue Type: Umbrella
>          Components: amv2
>            Reporter: stack
>            Priority: Major
>
> AMv2 is missing specification. There are too many grey-areas still. Also 
> missing are a concise listing of the tenets of AMv2 operation. Here are some 
> examples:
>  * HBASE-19529 "Handle null states in AM": Asks how we should treat null 
> state in hbase:meta. What does it 'mean'. We seem to treat it differently 
> dependent on context. Needs clarification. [~Apache9] recently asked similar 
> about the meaning of OFFLINE.
>  * Logging needs to have a particular form to help trace Procedure progress; 
> needs a write-up.
> Lets fill in items to address in this umbrella issue. Can address in 
> subissues and produce specification doc too. We have the below but these are 
> mostly (incomplete) description for devs on pv2 and amv2; the specification 
> is missing:
> http://hbase.apache.org/book.html#pv2
> http://hbase.apache.org/book.html#amv2
> (Other areas include addressing what is up w/ rollback -- when, how much, and 
> when it is not appropriate -- as well as recommendation on Procedures 
> coarseness, locking -- is it ok to lock table in alter table procedure for 
> the life of the procedure? -- and so on).



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