orchestrator-kubernetes: suppress minDomains when availability_zones is set#36516
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jubrad merged 3 commits intoMay 12, 2026
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…is set When `availability_zones` pins pods to specific AZs via node affinity, the number of eligible topology domains is constrained. If `minDomains` exceeds the number of pinned zones, Kubernetes treats the global minimum as 0, and with `maxSkew=1` only one pod can be scheduled — leaving additional replicas stuck pending. Fix by suppressing `minDomains` in the topology spread constraint whenever `availability_zones` is set, matching the existing behavior for soft spread constraints. Fixes CLO-74 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Extract topology_spread_min_domains helper and add unit test covering the four suppression cases: soft spread, az-pinned, both, and neither. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Alphadelta14
approved these changes
May 12, 2026
| }, | ||
| min_domains: topology_spread_min_domains( | ||
| config.soft, | ||
| availability_zones.is_some(), |
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this is fine for clusters of our size, but if we were to pin to say 4 AZs, then having minDomains as 2 or 3 is totally reasonable.
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Totally! It's possible this should just be a var on environmentd to make it more configurable.
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Problem
When
availability_zonespins pods to specific AZs via node affinity,minDomainswas still being applied to the topology spread constraint.minDomainstells the scheduler "there must be at least N eligible topology domains." IfminDomainsexceeds the number of pinned zones, Kubernetes treats the global minimum as 0 — and withmaxSkew=1, only one pod can be scheduled at a time, leaving additional replicas stuck pending indefinitely.Fixes CLO-74.
Solution
Suppress
minDomainsin theTopologySpreadConstraintwhenavailability_zonesis set, mirroring the existing behavior for soft spread constraints. A warning is logged whenmin_domainsis configured but will be ignored.Testing
See follow-up commit for unit test.