kvserver: small changes

[wenyihu6]

Epic: none
Release note: none

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allocator: move isDecommissionAction to allocatorimpl

This commit refactors isDecommissionAction into allocatorimpl for consistency
with other similar helpers like allocatorActions.{Add,Replace,Remove}. This
change has no behavior changes but to make future commits easier.

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kvserver: simplify logging in maybeEnqueueProblemRange

This commit simplifies the logging in maybeEnqueueProblemRange to log two
booleans directly.

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kvserver: fix comment when dropping due to exceeding size

Previously, the comment on the queue incorrectly stated that it removes the
lowest-priority element when exceeding its maximum size. This was misleading
because heap only guarantees that the root is the highest priority, not that
elements are globally ordered. This commit updates the comment to clarify that
the removed element might not be the lowest priority. Ideally, we should drop
the lowest priority element when exceeding queue size, but heap doesn't make
this very easy.

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kvserver: add logging for ranges dropped from base queue

This commit adds logging for ranges dropped from the base queue due to exceeding
max size, improving observability. The log is gated behind V(1) to avoid
verbosity on nodes with many ranges.

[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[cockroach-teamcity]

This change is 

[arulajmani]

modulo comments

@arulajmani reviewed 2 of 2 files at r1, 1 of 1 files at r2, 1 of 1 files at r3, 1 of 1 files at r4, 1 of 1 files at r5, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @tbg)

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-- commits line 33 at r5:
Did you mean to keep this fixup?

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pkg/kv/kvserver/queue.go line 776 at r4 (raw file):

	if pqLen := bq.mu.priorityQ.Len(); pqLen > bq.maxSize {
		replicaItemToDrop := bq.mu.priorityQ.sl[pqLen-1]
		log.Dev.VInfof(ctx, 1, "dropping due to exceeding queue max size: priority=%0.3f, replica=%v",

nit: Should this be in KVDistribution?

[wenyihu6]

pkg/kv/kvserver/queue.go line 776 at r4 (raw file):

Previously, arulajmani (Arul Ajmani) wrote…

nit: Should this be in KVDistribution?

Hm, was wondering abt this as well. But other logs in this file use log.Dev, and this is for base queue which is used for other queues outside of kv distribution, such as mvccGC.

[wenyihu6]

Rebased on master and picked up the fixup.

[wenyihu6]

TFTR!

bors r=arulajmani

[craig]

Build succeeded:

• linux_amd64_build
• local_roachtest_fips
• acceptance
• check_generated_code
• lint
• unit_tests
• linux_amd64_fips_build
• examples_orms
• docker_image_amd64
• local_roachtest