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kvserver: introduce cpu rebalancing #96127

Merged
merged 3 commits into from
Feb 9, 2023
Merged

kvserver: introduce cpu rebalancing #96127

merged 3 commits into from
Feb 9, 2023

Commits on Feb 9, 2023

  1. kvserver: pass load dimension to test load ranges 

    Previously `Queries` was hardcoded as the dimension to use when creating
test ranges for use in store rebalancer tests. This patch enables
passing in any `dimension`.

Release note: None
    @kvoli
    kvoli committed Feb 9, 2023
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  2. kvserver: refine est impact for lease transfers 

    Previously, when estimating the impact a lease transfer would have, we
would not differentiate between rebalance/transfer. This commit adds a
utility method `TransferImpact` to `RangeUsageInfo` which is now used
when making estimations about lease transers.

Currently, this is identical to `Load`, which was previously used
instead for transfers.

Release note: None
    @kvoli
    kvoli committed Feb 9, 2023
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  3. kvserver: introduce cpu rebalancing 

    This patch allows the store rebalancer to use CPU in place of QPS when
balancing load on a cluster. This patch adds `cpu` as an option with the
cluster setting:

`kv.allocator.load_based_rebalancing.objective`

When set to `cpu`, rather than `qps`. The store rebalancer will perform
a mostly identical function, however, it will target balancing the sum
of all replica's cpu time on each store, rather than qps. The default
remains as `qps` here.

Similar to QPS, the rebalance threshold can be set to allow controlling
the range above and below the mean store CPU is considered imbalanced,
either overfull or underfull respectively:

`kv.allocator.cpu_rebalance_threshold`: 0.1

In order to manage with mixed versions during upgrade and some
architectures not supporting the cpu sampling method, a rebalance
objective manager is introduced in `rebalance_objective.go`. The manager
mediates access to the rebalance objective and overwrites it in cases
where the objective set in the cluster setting cannot be supported.

resolves: cockroachdb#95380

Release note (ops change): Add option to balance cpu time (cpu)
instead of queries per second (qps) among stores in a cluster. This is
done by setting `kv.allocator.load_based_rebalancing.objective='cpu'`.
`kv.allocator.cpu_rebalance_threshold` is also added, similar to
`kv.allocator.qps_rebalance_threshold` to control the target range for
store cpu above and below the cluster mean.
    @kvoli
    kvoli committed Feb 9, 2023
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