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From "Matteo Bertozzi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15128) Disable region splits and merges in HBCK
Date Thu, 28 Jan 2016 23:57:39 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15128?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15122569#comment-15122569
] 

Matteo Bertozzi commented on HBASE-15128:
-----------------------------------------

{quote}Hmm, we actually do not have configuration options to enable / disable balancer. They
are usually always on of course. Only turned off in maintenance mode. So they are really not
configuration related.{quote}
they are not configuration, because we don't have dynamic configuration. 
pretty sure if we had dynamic conf, we ended up with a conf.set("xyz.enable", ...)

assuming we add this setSwitch() now, and later we add dynamic conf. how one decide when to
use one vs the other? since they are able to do the same thing?

{quote}The new split or merge switch is not directly related to normalizer. It allows to disable
all splits or merges, rather than changing normalizer behavior to do splits or merges.{quote}
this is just me not knowing what the normalizer is. I was assuming the normalizer was taking
care of all the split/merge related stuff now. sorry, but I haven’t looked at that code
yet and I was just making an assumption.
and the switch we had already for the normalizer seemed a good place to keep down the number
of rpc calls that will end up "redundant" if we add dynamic configuration support.

> Disable region splits and merges in HBCK
> ----------------------------------------
>
>                 Key: HBASE-15128
>                 URL: https://issues.apache.org/jira/browse/HBASE-15128
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Enis Soztutar
>            Assignee: Heng Chen
>             Fix For: 2.0.0, 1.3.0
>
>         Attachments: HBASE-15128.patch, HBASE-15128_v1.patch, HBASE-15128_v3.patch
>
>
> In large clusters where region splits are frequent, and HBCK runs take longer, the concurrent
splits cause further problems in HBCK since HBCK assumes a static state for the region partition
map. We have just seen a case where HBCK undo's a concurrently splitting region causing number
of inconsistencies to go up. 
> We can have a mode in master where splits and merges are disabled like the balancer and
catalog janitor switches. Master will reject the split requests if regionservers decide to
split. This switch can be turned on / off by the admins and also automatically by HBCK while
it is running (similar to balancer switch being disabled by HBCK). 
> HBCK  should also disable the Catalog Janitor just in case. 



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