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https://issues.apache.org/jira/browse/HBASE-26726?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17484973#comment-17484973
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Bryan Beaudreault commented on HBASE-26726:
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I'm personally against changes like this, would rather see the bugs fixed or
feature removed. For a similar reason you've provided on new features with too
many config params ("what is an operator supposed to set it to?"). In this
case, there's a feature but there's an option to disable it with git blame
pointing back to a Jira listing various issues with it. This is pretty scary
for a new hbase user or existing upgrading user. It just adds to the burden of
things they need to read into and totally understand or just disable out of
expedience and potentially never re-evaluate. A config like this, down the
road, begs the question of who still uses the feature and when if ever can we
delete it?
Just my 2 cents.
> Allow disable of region warmup before graceful move
> ---------------------------------------------------
>
> Key: HBASE-26726
> URL: https://issues.apache.org/jira/browse/HBASE-26726
> Project: HBase
> Issue Type: Improvement
> Components: master, Region Assignment
> Reporter: Andrew Kyle Purtell
> Assignee: Andrew Kyle Purtell
> Priority: Minor
> Fix For: 2.5.0, 2.6.0, 3.0.0-alpha-3
>
>
> We have encountered two issues with region warmup before the assignment
> manager gracefully moves a region from one regionserver to another.
> The first instance is HBASE-26722. Part of the failure chain is temporary
> double assignment like conditions where both the source and destination
> regionservers think they have exclusive rights to storefile management (as
> they should) but warmup opens a region before it is closed and then both
> regionservers take compaction related actions. While this can be remediated
> with more care to this case, it is unclear if warmup affords significant
> advantage. The motivation of the original commit in 2015 introducing this
> feature was avoidance of blockcache misses once region ownership transfer was
> advertised to clients. Depending on use case and additional default-false
> schema options (like preload) this could be valuable. Or not.
> The second instance is in place upgrade from HBase 1 to HBase 2. In a
> scenario where regionservers have been replaced by HBase 2 versions, but the
> master is still HBase 1, the region warmup RPC request fails. This is not
> particularly harmful but indicates it will not be useful during the
> transition period.
> We think it would be good to allow for warmup before move to be optionally
> disabled by a site configuration setting. In particular there have been many
> unrelated changes committed since 2015 and expectations of invariants in the
> contribution of the warmup-on-move feature have been invalidated. HBASE-26722
> may be the only case, or it might not. This is a fairly trivial change.
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