[jira] [Commented] (HBASE-20830) Document that region replica does not work well with AMv2

["Xinhui Xu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-20830?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16833278#comment-16833278 ] 

Xinhui Xu commented on HBASE-20830:
-----------------------------------

trying to ping [~Apache9] for more details about this issue

the background is we might use region replica feature on version 2.2.0 in near future, and get confused after seeing this issue

except the potential region replica reopen issue already mentioned in HBASE-21644 , wonder in which senarios that AM won't work well with region replica feature, it'll be much more straightforward if you can name some of them for me. thanks. 

by the way that I found those TODOs in the code of AM which are closly related with region replica feature are few

> Document that region replica does not work well with AMv2
> ---------------------------------------------------------
>
>                 Key: HBASE-20830
>                 URL: https://issues.apache.org/jira/browse/HBASE-20830
>             Project: HBase
>          Issue Type: Sub-task
>          Components: documentation
>            Reporter: Duo Zhang
>            Assignee: Duo Zhang
>            Priority: Major
>             Fix For: 3.0.0
>
>         Attachments: HBASE-20830.patch
>
>
> As we can see lots of TODOs for region replica feature in the AssignmentManager' code. And also, now we rely on the openSeqNum to determine whether a region has been successfully reopened, but the openSeqNum for a non-default replica region seems unstable...
> It is too late for the 2.1.0 release so let's just add a note in ref guide to say that region replica does not work well with AMv2 first, and then start to make it stable in follow on minor or major release lines.



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