jakman85andClaude Opus 5
5642881c4d
MEASURED on prod 2026-10-18: kube-system/coredns had replicas: 1. In-cluster DNS was a single pod on a single node, so draining or rebooting that node was a CLUSTER-WIDE in-cluster DNS outage until the pod rescheduled -- every Service lookup, every CNPG replica finding its primary, every operator addressing the API by name. It was invisible because 1/1 Ready looks healthy. It is urgent rather than latent now: the scheduled reboot automation on feat/automated-upgrades drains and reboots one node at a time, unattended, overnight -- turning a single point of failure into a recurring one. WHY AN HPA AND NOT replicas: 2 -- the whole decision. k3s OWNS the coredns Deployment: AddOn/coredns, source /data/k3s/server/manifests/coredns.yaml, managedFields managers deploy@k3s-prod-1 + k3s, objectset.rio.cattle.io/hash label. k3s re-stages its bundled manifests on startup, so replicas: 2 written there -- or a kubectl scale -- is reverted on the next restart or upgrade. Rejected alternatives: * coredns.yaml.skip + our own templated copy (the roles/kube_vip pattern). Deterministic, but takes ownership of coredns from k3s permanently so k3s upgrades stop updating it. Too high a price for a replica count. * A Flux patch of the Deployment. Rejected outright: Flux and k3s's deploy controller would both own one object and fight -- the default-deny NetworkPolicy drift-loop shape (~2500 events/10min) this cluster already hit. An HPA is a separate object k3s does not own, driving /scale rather than the Deployment spec, so there is no shared-ownership fight; if k3s re-stages replicas: 1 it is re-asserted within a reconcile. Disclosed cost: a brief window at 1 replica after a k3s restart. It is a FLOOR-HOLDER, not an autoscaler -- the CPU metric exists only so the autoscaling/v2 object is valid. Measured: 5m/4m against a 100m request (~5%), so the 80% target is never approached. scaleDown stabilization 600s because DNS is the worst thing to flap; scaleUp immediate, since that restores redundancy. The kustomization edit is ADDITIVE: platform/coredns/ already existed and holds the coredns-custom split-horizon ConfigMap (R-DNS-01/03), which is untouched. UNAPPLIED. The HPA has never run, and the claim that k3s reverts replicas on restart is reasoned, not observed. After merge check `describe hpa coredns` for ScalingActive=True -- an inert HPA looks identical to a working one because the hand scale already left 2 replicas. See the handoff entry. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
platform/
Cluster-wide platform services, Flux-managed (R-PLAT-01, R-GITOPS-01/02/03). Reconciled
by the platform Flux Kustomization defined in clusters/base/platform.yaml,
before apps/.
Governing spec: docs/05-gitops-and-delivery.md,
docs/01-architecture-overview.md.
Phase 0 scaffolding only. Every component here is a structurally-correct stub — a Flux HelmRelease and/or Kustomization with a values placeholder, a README citing the governing ADR/spec, and TODOs for the phase that fills it in. No cluster exists; nothing reconciles yet. Do not add working config, secrets, or provisioning under Phase 0 (spec
AGENTS.md§1/§5/§6,roadmap/phases.md).
Reconciliation flow (how a change lands)
git (source of truth)
│ operator PR → CI (lint · schema · Kyverno L0 · Chainsaw) → merge to tracked branch
▼
Flux GitRepository (clusters/base/flux-system.yaml)
▼
Flux Kustomization "platform" → ./platform (this dir) ── substituteFrom cluster-vars ──┐
│ prune=true (drift correction, R-GITOPS-03) · wait=true │ R-ENV-02
▼ │
Flux Kustomization "apps" → ./apps (dependsOn platform) ─ substituteFrom cluster-vars ──┘
Git is authoritative; the cluster conforms to git and drift is auto-corrected (R-GITOPS-01/03).
Manual kubectl apply of platform state is prohibited (spec AGENTS.md §5).
The dev ↔ prod overlay model (R-ENV-02)
Platform manifests are authored once. Every value that legitimately differs between environments
is a ${TOKEN} resolved from the cluster-vars ConfigMap via Flux postBuild.substituteFrom. The
clusters/dev and clusters/prod overlays differ only by the values they patch into
cluster-vars (issuer, replica counts, storage sizes, retention). See
clusters/README.md. Base manifests are never forked per environment.
Components (one directory each)
| Dir | Component | Governing ADR / spec | Serves |
|---|---|---|---|
cilium/ |
CNI + kube-proxy replacement + Gateway API + Egress Gateway + Hubble | ADR-0002, docs/03 | R-NET-* |
longhorn/ |
Replicated block storage; 3-replica default StorageClass + bulk tier | ADR-0003, docs/04 | R-STATE-* |
cert-manager/ |
TLS via Let's Encrypt DNS-01 (Cloudflare); staging + prod ClusterIssuers | ADR-0006, docs/08 | R-TLS-* |
externaldns/ |
Automatic DNS records for public services (Cloudflare) | docs/09 | R-DNS-* |
gateway/ |
Gateway API GatewayClass + shared HTTPS Gateway + wildcard cert | ADR-0002/ADR-0006, docs/09 | R-DNS-01, R-TLS-01 |
monitoring/ |
kube-prometheus-stack + Loki + Grafana Alloy + Alertmanager | docs/10 | R-OBS-* |
velero/ |
Off-cluster backup/DR of volumes + resource state | ADR-0003, docs/04 | R-STATE-03 |
kubevirt/ |
KubeVirt + CDI (IaaS: application VMs on the same K8s surface) | ADR-0005, docs/06 | R-PLAT-03 |
image-automation/ |
Flux image-update-automation (hands-off image tag advance) | ADR-0009, docs/11 | R-UPD-02 |
keycloak/ |
Platform IdP (OIDC + SAML), config-as-code, PostgreSQL on Longhorn | ADR-0014, docs/15 | R-IDP-* |
oauth2-proxy/ |
Forward-auth at the Gateway for non-OIDC apps → Keycloak | ADR-0014, docs/15 | R-IDP-* |
kyverno/ |
L0 policy-as-code gate — OWNED BY THE POLICY ENGINEER (WS-TEST). | ADR-0011, docs/14 | R-TEST-* |
⚠️ INTEGRATION TODO(PM): wire kyverno into the platform kustomization
platform/kyverno/ is authored by a different agent (the policy engineer, WS-TEST). This
workstream did not create any files under platform/kyverno/ and must not.
platform/kustomization.yaml intentionally omits - kyverno. Once the
policy engineer's files land, the PM must add - kyverno to that list (recommended first, so
policies are present before other components reconcile). The line is present as a commented TODO in
the kustomization.
Secrets
Every secret referenced below (Cloudflare API token, Velero backup-target creds, Keycloak admin/DB, oauth2-proxy cookie/client secrets) is referenced by name only and will be committed SOPS-encrypted (WS-SEC, ADR-0007). No plaintext secret appears anywhere in this tree.
Cross-workstream contracts surfaced by these stubs
- cilium (WS-NET ↔ WS-INFRA): Cilium's initial CNI install is done by Ansible at cluster bootstrap (docs/02, Phase 1). The HelmRelease here manages Cilium config thereafter; its Helm values MUST match the Ansible bootstrap values (kubeProxyReplacement, k8sServiceHost/Port, API server host) or reconciliation will fight the bootstrap. Contract owner: WS-NET + WS-INFRA.
- gateway + cert-manager + externaldns (WS-NET + WS-SEC): the shared Gateway listener, the
wildcard
*.home.keithjackson.devcert, and the ExternalDNS source all reference each other; they form the "Issuer + Gateway TLS" interface inroadmap/workstreams.md. - image-automation (WS-UPDATE): this dir holds only the cluster-wide ImageUpdateAutomation +
git write-back. Per-service
ImageRepository/ImagePolicyare rendered from each ServiceDefinition'supdateblock (WS-GITOPS/WS-UPDATE), living withapps/. - keycloak/oauth2-proxy (WS-SEC): the SSO/auth contract (
authblock → Keycloak client / oauth2-proxy protection) is owned by WS-SEC; these are placeholders pending that contract.