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https://issues.apache.org/jira/browse/HBASE-20828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16590242#comment-16590242
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stack commented on HBASE-20828:
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Another idea that has been coming up in discussion (Suggested by [~Apache9]) is 
that a Procedure should be able to say 'holdLock' for a subset of its lifetime. 
The illustration is ModifyTable where it should be able to release the global 
lock when reassigns start. TODO.

> 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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