Andrew Kyle Purtell created HBASE-26726:
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Summary: 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
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. 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 still 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where regionservers have been replaced by HBase 2 versions, but the master is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, region warmup fails. This is not particular 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.
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