feat(shutdown): configure graceful node shutdown, and never scale a Delete-policy StatefulSet

All three nodes had to be powered off to move them onto a UPS, and there was
NO procedure: infra/cluster.sh stop is virsh-based and only ever applied to the
decommissioned dev cluster. The sequence was improvised live. Two defects came
out of doing it.

1. GRACEFUL NODE SHUTDOWN WAS UNCONFIGURED ON EVERY PROD NODE. No
   shutdownGracePeriod anywhere in infra/ansible/, so `shutdown -h` stopped k3s,
   containerd went with it, and every pod was SIGKILLed where it stood -- 9 CNPG
   instances mid-checkpoint, the UniFi VM, 25 attached Longhorn volumes.
   roles/k3s_server now sets kubelet-arg shutdown-grace-period=90s and
   shutdown-grace-period-critical-pods=20s.

   The half that silently defeats the other half: this is enforced by LOGIND,
   not the kubelet. The kubelet holds an inhibitor DELAY lock and systemd waits
   at most InhibitDelayMaxSec -- DEFAULT 5 SECONDS -- then proceeds regardless,
   truncating the drain with no error. The role ships a logind.conf.d drop-in
   (120) and ASSERTS cap >= grace period, because the failure is invisible.

2. SCALING A StatefulSet TO 0 DELETED ITS PVC AND VOLUME. monitoring/loki
   carries persistentVolumeClaimRetentionPolicy whenScaled: Delete, so the
   quiesce destroyed storage-loki-0 outright. Loki stores type: filesystem, so
   that PVC was the only copy; 72h retention bounded the loss, the mechanism
   does not. Symptom was the volume count going 25 -> 24, first misread as a
   miscount. Repaired: scale back to the declared 1 recreated the PVC and
   loki-0 is 2/2 Running.

New infra/maintenance/quiesce.sh (quiesce|resume|status) encodes the sequence
that worked and REFUSES to scale any whenScaled: Delete StatefulSet -- it stays
running, its volume hard-detaches, and it rebuilds on restart. A rebuild beats
a deletion. Discovery is computed from the live cluster, so a newly onboarded
service needs no edit here.

runbooks/cluster-maintenance-shutdown.md is the operator page: order in both
directions, TrueNAS-after-nodes (hard NFS mount wedges kubelet), the
un-hibernate-Postgres step Flux will NOT do for you, and a "looks broken but is
fine" section separating the 4/19 Flux cascade, the degraded-and-rebuilding
volume and the self-recovering keycloak-operator from the one thing that needs
a human (a stuck oauth2-proxy replica).

THE KUBELET CHANGE HAS NEVER BEEN APPLIED OR TESTED -- it needs a rolling k3s
restart, which is an operator action. Review config.yaml's kubelet-arg before
applying: a bad config.yaml is how k3s fails to come up. See the handoff entry.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

decisions/2026-10-17-graceful-cluster-shutdown.md

@@ -0,0 +1,106 @@
+---
+date: 2026-10-17
+branch: feat/graceful-cluster-shutdown
+title: "Graceful node shutdown was never configured, and scaling a StatefulSet deleted its PVC"
+---
+
+## What changed
+
+All three nodes had to be powered off to move them onto a UPS. There was **no procedure for it**:
+`infra/cluster.sh stop` is `virsh`-based and only ever applied to the decommissioned dev cluster, so
+the whole sequence was improvised live. Two defects came out of doing it.
+
+**1. Kubelet graceful node shutdown was unconfigured on every prod node.** No `shutdownGracePeriod`
+anywhere in `infra/ansible/`, so `shutdown -h` stopped k3s, containerd went with it, and every pod
+was SIGKILLed where it stood — 9 CloudNativePG instances mid-checkpoint, the UniFi VM, and 25
+attached Longhorn volumes. `roles/k3s_server` now writes `kubelet-arg` into
+`/etc/rancher/k3s/config.yaml` with `shutdown-grace-period=90s` and
+`shutdown-grace-period-critical-pods=20s`.
+
+The half that is easy to miss and silently defeats the other half: **graceful node shutdown is
+enforced by logind, not by the kubelet.** The kubelet holds an inhibitor *delay* lock and systemd
+waits at most `InhibitDelayMaxSec` — **default 5 seconds** — before proceeding regardless. A grace
+period above that cap is truncated with no error, so the feature looks configured and still
+hard-kills pods. The role now ships a `logind.conf.d` drop-in setting it to 120, and **asserts**
+`k3s_logind_inhibit_delay_max_sec >= k3s_kubelet_shutdown_grace_period` rather than documenting the
+relationship, because the failure is invisible.
+
+**2. Scaling a StatefulSet to 0 DELETED its PVC and Longhorn volume.** `monitoring/loki` carries
+`persistentVolumeClaimRetentionPolicy: {whenDeleted: Delete, whenScaled: Delete}`, so the quiesce's
+`scale --replicas=0` destroyed `storage-loki-0` outright. Loki stores with `type: filesystem`, so
+that PVC was the only copy of its log data. This is the defect in this change set that actually
+destroyed something, and it was mine.
+
+New `infra/maintenance/quiesce.sh` (`quiesce` | `resume` | `status`) encodes the sequence that
+worked, and **refuses to scale any StatefulSet whose `whenScaled` is `Delete`** — it leaves it
+running, accepts that its volume hard-detaches at poweroff, and prints which volumes to expect
+`degraded`. A rebuild is a vastly better outcome than a deletion. Workload discovery is computed
+from the live cluster (every Deployment/StatefulSet whose pods mount a PVC, Longhorn or TrueNAS NFS)
+rather than hardcoded, so a newly onboarded service is covered without anyone remembering to add it.
+
+`runbooks/cluster-maintenance-shutdown.md` (new, registered in `runbooks/kustomization.yaml`) is the
+operator page: shutdown order, the TrueNAS-after-nodes constraint, power-on order, the
+un-hibernate-Postgres step Flux will not do for you, and a "what looks broken but is fine" section
+separating the `4/19`-Kustomizations-Ready cascade, the degraded-and-rebuilding volume and the
+self-recovering `keycloak-operator` from the one thing that genuinely needs a human (a stuck
+`oauth2-proxy` replica).
+
+## What I verified
+
+* **Graceful shutdown was genuinely absent**, not merely undocumented: `grep -rn
+  'shutdownGracePeriod|graceful-node-shutdown'` over `infra/ansible/` returns nothing, and no
+  `logind` or `InhibitDelay` setting exists anywhere in the tree.
+* **The whole shutdown/restart cycle was executed end to end on prod 2026-10-17** and the cluster
+  came back: 3/3 nodes Ready with etcd `healthz` ok, 19/19 Flux Kustomizations Ready,
+  `platform-config`'s `lastAppliedRevision` equal to the GitRepository artifact revision, all 3
+  CNPG clusters `healthy` with primaries elected, the UniFi VM `Running`, PiHole resolving
+  (`home.keithjackson.dev` → `192.168.2.20` via `192.168.2.23`), and the Gateway serving
+  `200/200/401` for apex/gitea/plex.
+* **The PVC-deletion mechanism is confirmed, not inferred:** `kubectl get sts loki -o
+  jsonpath={.spec.persistentVolumeClaimRetentionPolicy}` returns
+  `{"whenDeleted":"Delete","whenScaled":"Delete"}`, the PVC was `NotFound` after the cycle, and the
+  Longhorn volume count had gone 25 → 24.
+* **The damage was repaired and verified:** `scale sts loki --replicas=1` (restoring the replica
+  count the chart declares) recreated `storage-loki-0` as a fresh 50Gi Bound PVC, `loki-0` reached
+  `2/2 Running`, and the volume count returned to 25.
+* **The guard works against the live cluster**, tested both ways: `sts_deletes_pvc_on_scale
+  monitoring loki` returns true (would be skipped) and `pihole pihole` returns false (safe to
+  scale).
+* **The script's read-only paths run clean on prod:** `status` reports correctly, and the discovery
+  function returns the 13 workloads currently holding a PVC.
+* `bash -n` clean; the two edited Ansible YAML files parse.
+
+## What I did NOT verify
+
+* **The kubelet change has NEVER BEEN APPLIED OR TESTED.** This is the significant gap. I did not
+  run the role, did not restart k3s, and have **not** observed a node actually drain on
+  `shutdown -h`. Everything about it is reasoning from kubelet/systemd semantics plus the measured
+  absence of the setting. Applying it needs a **rolling** k3s restart (`serial: 1` — kube-vip keeps
+  the API up, etcd holds at 2/3), which is an operator action (CLAUDE.md §5). **Verify by draining
+  one node for real:** apply, then `shutdown -h now` on a single node and watch whether pods
+  terminate gracefully instead of vanishing.
+* **Whether 90s/20s are the right numbers.** Chosen to comfortably cover a Postgres fast shutdown
+  and a Longhorn flush; not measured against either. The budget is spent on every reboot, so if a
+  node takes noticeably longer to go down, this is why.
+* **Whether k3s accepts `kubelet-arg` in `config.yaml` as written.** The file already carries
+  `kube-apiserver-arg` as a list and `kubelet-arg` is the documented sibling, but I did not render
+  or apply it, so a typo would surface only at k3s restart — and a bad `config.yaml` is exactly the
+  kind of thing that makes k3s fail to come up. **Review this one before applying.**
+* **The `assert` task's `regex_replace` on the grace period** assumes a plain `90s`-style value; a
+  value expressed as `1m30s` would parse to the nonsense integer `130`. Fine for the committed
+  defaults, wrong if someone writes a compound duration.
+* **`resume`'s Flux-reconcile wait has never run**, and neither has `quiesce` as a script — the
+  2026-10-17 cycle was done with the equivalent commands by hand, so the script encodes a sequence
+  that worked but has not itself been executed end to end. Only `status` and the discovery and guard
+  functions have run.
+* **Loki's lost log window is gone for good.** Up to 72h of logs (its `retention_period`), destroyed
+  by my scale-down. Nothing recovers it; Velero's schedules cover the namespace but the PVC was
+  deleted, not corrupted, and I did not attempt a restore because the data self-expires anyway.
+* **No other `whenScaled: Delete` StatefulSet was audited.** The guard now catches them generically,
+  but I did not enumerate which other workloads carry the policy, so I cannot say loki was the only
+  one at risk. The runbook gives the one-liner to list them.
+* **TrueNAS and the router are entirely outside this change.** TrueNAS is not in the Ansible
+  inventory and refuses SSH, so its shutdown stays a web-UI step with no automation and no check.
+* **No runtime conformance.** `vars.CLUSTER_AVAILABLE` is still unset, so CI proves the L0/L1
+  offline subset only.
+* I did not re-measure branch protection or runner state (CLAUDE.md §2b).