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From "Mikhail Antonov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15065) SimpleRegionNormalizer should return multiple normalization plans in one run
Date Wed, 06 Jan 2016 22:25:39 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15086396#comment-15086396

Mikhail Antonov commented on HBASE-15065:

On the patch..

 - do we not need regionSizeComparator anymore, and Collections.sort(regionsWithSize, regionSizeComparator)
before we consider candidates for the merge? Now we just merge any two adjacent (since the
original list of regions is sorted the way so they are all adjacent, right?) regions where
r1+r2<avg. I assume that's fine.
  -One note here..we compute bunch of plans in one pass, without recomputing the avg size.
So say we have regions with sizes 10, 10, 10, 60. Avg size would be 22.5, so with this logic
we merge 2 out of 3 10-size regions and split 60. Do we want that, or should we recompute
avg on each loop iteration, pretending that we already applied the proposed change?
 - I think if we compute plans all in once, we can run them concurrently more than 1 at a
time. Running serial is probably good enough for now, but may be too slow to keep up with
ongoing data distribution skew on large write-heavy clusters? Ideally we would run configurable
N  number of normalization ops at the moment, or not more than X percent of total number of
regions in this table?
 - Regarding priority, I think with computing and running multiple plans concurrently it's
not necessary to give splits more priority. No harm to leave it sorted either. I'm agnostic.

> SimpleRegionNormalizer should return multiple normalization plans in one run
> ----------------------------------------------------------------------------
>                 Key: HBASE-15065
>                 URL: https://issues.apache.org/jira/browse/HBASE-15065
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Ted Yu
>            Assignee: Ted Yu
>         Attachments: 15065-v1.txt
> This is follow up to HBASE-14867 w.r.t. SimpleRegionNormalizer
> Outline for enhancements:
> * adjustment to the period when SimpleRegionNormalizer runs
> * explore merge opportunities among all neighboring region pairs
> * return multiple normalization plans

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