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https://issues.apache.org/jira/browse/HBASE-18105?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16137888#comment-16137888
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stack commented on HBASE-18105:
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[~easyliangjob] Thank you for digging in.
I like your reasoning on why an HRI has SPLIT in it. The alternative would be a
new column in hbase:meta that had state in it. We already have info:splitA,
info:splitB, info:mergeA, and info:mergeB columns which are probably badly
named now I look at them but marking a parent region as split in a column in
hbase:meta would go w/ our writing of splitA and splitB as hbase:meta columns
better than setting flag in HRI. File a TODO I'd say? In this issue, add your
nice reasoning as a comment on the split method?
(i thought we were putting region state already -- i.e. OPENING, OPEN -- into
hbase:meta but I was wrong -- we just update locations as region goes through
its stages).
bq. Overall, there are still some places in split and merge needs to be cleaned
up.
What you thinking [~easyliangjob]?
Thanks for doing this great cleanup.
> [AMv2] Split/Merge need cleanup; currently they diverge and do not fully
> embrace AMv2 world
> -------------------------------------------------------------------------------------------
>
> Key: HBASE-18105
> URL: https://issues.apache.org/jira/browse/HBASE-18105
> Project: HBase
> Issue Type: Sub-task
> Components: Region Assignment
> Affects Versions: 2.0.0
> Reporter: stack
> Fix For: 2.0.0
>
>
> Region Split and Merge work on the new AMv2 but they work differently. This
> issue is about bringing them back together and fully embracing the AMv2
> program.
> They both have issues mostly the fact that they carry around baggage no
> longer necessary in the new world of assignment.
> Here are some of the items:
> Split and Merge metadata modifications are done by the Master now but we have
> vestige of Split/Merge on RS still; e.g. when we SPLIT, we ask the Master
> which asks the RS, which turns around, and asks the Master to run the
> operation. Fun. MERGE is all done Master-side.
>
> Clean this up. Remove asking RS to run SPLIT and remove RegionMergeRequest,
> etc. on RS-side. Also remove PONR. We don’t Points-Of-No-Return now we are up
> on Pv2. Remove all calls in Interfaces; they are unused. Make RS still able
> to detect when split, but have it be a client of Master like anyone else.
> Split is Async but does not return procId
> Split is async. Doesn’t return the procId though. Merge does. Fix. Only hard
> part here I think is the Admin API does not allow procid return.
> Flags
> Currently OFFLINE is determined by looking either at the master instance of
> HTD (isOffline) and/or at the RegionState#state. Ditto for SPLIT. For MERGE,
> we rely on RegionState#state. Related is a note above on how split works --
> there is a split flag in HTD when there should not be.
>
> TODO is move to rely on RegionState#state exclusively in Master.
> From Split/Merge Procedures need finishing in
> https://docs.google.com/document/d/1eVKa7FHdeoJ1-9o8yZcOTAQbv0u0bblBlCCzVSIn69g/edit#heading=h.4b60dc1h4m1f
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