backport-2.1: storage: make load-based replica rebalancing decisions at the store level #29663
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Follow-up to cockroachdb#28340, which did this for just leases. Fixes cockroachdb#17979 Release note (performance improvement): Range replicas will be automatically rebalanced throughout the cluster to even out the amount of QPS being handled by each node.
This leaves properly cleaning up the code for later, but ensures that the existing cluster setting will enable store-level rebalancing rather than the old experimental write/disk-based rebalancing. Release note: None
It's identical to the test for load-based lease rebalancing, just with more than 3 nodes such that replicas must be rebalanced in addition to leases in order for load to be properly spread across all nodes. Release note: None
This cleans up all the old code, settings, and tests without massively overhauling the structure of things. More could be done to simplify things, but this is the least intrusive set of changes that seem appropriate so late in the development cycle. Release note (backwards-incompatible change): The experimental, non-recommended stat-based rebalancing setting controlled by the kv.allocator.stat_based_rebalancing.enabled and kv.allocator.stat_rebalance_threshold cluster settings has been removed and replaced by a new, better supported approach to load-based rebalancing that can be controlled via the new kv.allocator.load_based_rebalancing cluster setting. By default, leases will be rebalanced within a cluster to achieve better QPS balance.
Release note: None
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This change is |
BramGruneir
reviewed
Sep 6, 2018
complete! 0 of 0 LGTMs obtained
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Backport 5/5 commits from #28852.
/cc @cockroachdb/release
Built on top of #28340, which is where the first 3 commits are from. This is still somewhat incomplete, in that it's missing unit tests and I'm only just now running tpc-c 10k on it. Sending out now to start the discussion of whether to include it in 2.1, since we're obviously very late in the intended development cycle.