The pod-count backpressure source read
`apiserver_storage_objects{resource="pods"}` from an apiserver
`/metrics` scrape. That gauge is a periodically-refreshed cached count,
and it is served by whichever apiserver replica the scrape lands on —
replicas disagree with each other at the same instant, by enough to
swamp the engage/release hysteresis band. Engage and release timing was
therefore partly a function of scrape routing.
This replaces it with a single `limit=1` list of the workload namespace
and computes `remainingItemCount + items.length`. One pod object
transferred, no informer, no watch cache.
Two request-shape constraints are load-bearing and called out in the
code: passing a label or field selector makes the apiserver omit
`remainingItemCount` entirely, and setting `resourceVersion` serves a
cached count rather than a quorum read. Neither is passed.
`remainingItemCount` is only set when the list is truncated, so
`_continue` is the truncation signal — if it is absent the returned page
is the whole collection and `items.length` is already exact. If the list
*is* truncated and the count is missing or implausible, the fetcher
throws rather than guessing.
Failure semantics are unchanged: a throw lands in the monitor's existing
catch, exactly as the previous parse did. The hysteresis, verdict shape,
and gauge are untouched. RBAC is unchanged — the existing role already
grants `pods: list`.
The `/metrics` non-resource grant in the deployment role becomes unused,
and the scrape-timeout env var is now a slight misnomer. Both left alone
deliberately: the grant may be wanted again for other apiserver signals,
and renaming the var would need a coordinated config change for no
behavioural gain.
Tests cover the not-truncated, truncated, missing-count, negative-count
and timeout paths.
nicktrn
b42e5c3771