docs(decisions): record that PiHole HA is verified live, failover drill included

No manifests change. The three entries merged earlier today each say, correctly
at the time, that nothing had been reconciled -- which is now stale in exactly
the way CLAUDE.md section 2b warns about: a reader would conclude the work is
unproven. This entry is the current state and does not edit the earlier files.

Measured on live prod after dce20b7: apps-wave-0 reconciled in ~90s (inside the
5m timeout the multi-replica entry flagged as a risk); pihole-0 on k3s-prod-3
and pihole-1 on k3s-prod-2, so the required anti-affinity was satisfied; both
per-replica claims Bound; the old Deployment and the old unused PVC both pruned;
PDB healthy with one disruption allowed.

The mountPath fix is confirmed: /etc/pihole is now on /dev/longhorn with 6.9M
used on both pods, where it was previously on the overlay.

Phase 1's declarations reproduce onto a FRESH volume, which was the whole reason
for sequencing it first: 72,234 gravity domains rebuilt on each replica from the
declared adlist, and the declared SOPS secret authenticates on BOTH pods
("valid":true via each container's own env, value never printed).

FAILOVER DRILL, observed by the operator: a replica was deleted, recreated in
~30 seconds, and DNS never dropped a request. First direct evidence the replica
count delivers what it was added for.

Re-deriving the SLI from the rendered workload kind mattered concretely: the
StatefulSet series returns 2 while the old Deployment series now returns ZERO
series, so a stale Deployment-shaped rule would have matched its own absent()
branch and fired permanently -- a standing false page.

Still unverified and stated as such: node failure (the drill deleted a pod, so
the 300s toleration path is untouched), DNS during the cutover itself, two-node
loss, and the cluster-wide dependency that replicas cannot address.

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

decisions/2026-10-04-pihole-ha-verified.md

@@ -0,0 +1,117 @@
+---
+date: 2026-10-04
+branch: docs/pihole-ha-verified
+title: PiHole HA is VERIFIED on live prod — including a failover drill with zero dropped DNS queries
+---
+
+## What changed
+
+**No manifests changed. This entry exists to correct the log.** The three PiHole/Plex entries merged
+earlier today each say, correctly at the time, that nothing had been reconciled and that the outcome
+was unverified:
+
+- `decisions/2026-10-04-pihole-declare-state.md` — "Nothing here has been reconciled."
+- `decisions/2026-10-04-pihole-multi-replica.md` — "Nothing has been reconciled. No StatefulSet
+  exists, no second replica has ever run, the anti-affinity has never been evaluated..."
+
+All three are now **merged, reconciled and measured**, so those sentences are stale in exactly the way
+§2b of CLAUDE.md warns about — a reader who found them would conclude the work is unproven. This entry
+is the current state; it does not edit the earlier files (separate files, nothing to merge).
+
+Delivered and live as of 2026-10-04, from PRs #43 (plex tcp/32400), #44 (declare PiHole state) and
+#45 (PiHole 2 replicas + the mountPath bug):
+
+- PiHole is a **2-replica StatefulSet**, one pod per node, with per-replica Longhorn volumes, a
+  PodDisruptionBudget, and an `up` SLI that follows the rendered workload kind.
+- PiHole's admin password and adlists are **declared in git** and reproduce onto a fresh volume.
+- PiHole's config PVC is mounted where PiHole actually writes (`/etc/pihole`), which it was not before.
+
+## What I verified
+
+All measured against live prod on 2026-10-04, after the merge of #45 (`dce20b7`).
+
+**Reconcile.** `GitRepository` artifact `main@sha1:dce20b7`; `apps-wave-0`
+`lastAppliedRevision=main@sha1:dce20b7`, `Ready=True/ReconciliationSucceeded`. It completed in roughly
+**90 seconds**, well inside the Kustomization's `timeout: 5m` — the risk flagged in the multi-replica
+entry ("whether `pihole -g` finishes inside the 5 m timeout") did **not** materialise. A transient
+`Ready=False/DependencyNotReady: platform-config` seen mid-flight was the dependency cascade, not a
+failure; `platform-config` was already `Ready=True` at the new revision moments later.
+
+**Topology and objects.**
+
+| Measured | Value |
+|---|---|
+| pods / nodes | `pihole-0` → **k3s-prod-3**, `pihole-1` → **k3s-prod-2** (2/2 Running each) — the required anti-affinity was satisfied |
+| per-replica claims | `config-pihole-0`, `config-pihole-1` — both `Bound`, 2Gi |
+| old `pihole-config` PVC | **pruned** (it held only `lost+found`, so nothing was lost) |
+| old `pihole` Deployment | **pruned** — `No resources found in pihole namespace` |
+| PodDisruptionBudget | `minAvailable 1`, `disruptionsAllowed 1`, `currentHealthy 2` |
+
+**The mountPath bug is fixed.** `df` inside both pods reports `/etc/pihole` on
+`/dev/longhorn/pvc-...` with **6.9 M used** — previously it was on `overlay` while the Longhorn volume
+sat unused at `/data/config`. `backup.policy: daily-offcluster` now has real content to back up
+instead of reporting success over an empty volume.
+
+**Phase 1's declarations reproduce onto a FRESH volume — the point of doing it first.** Both replicas
+booted with an empty `/etc/pihole`:
+
+- **72,234 gravity domains** on each, rebuilt from the adlist declared in `catalog/pihole.yaml`.
+- **The declared SOPS secret authenticates on both pods.** `POST /api/auth` using the container's own
+  `FTLCONF_webserver_api_password` returned `"valid":true` on `pihole-0` **and** `pihole-1` — so
+  Secret → env → FTL's own hashing → working login, identically on both. (The secret's value was never
+  printed; an earlier reading of `pwhash` as "unset" was a quoting bug in the check, disproven by an
+  empty password being rejected with `password incorrect` and then by this positive test.)
+
+**User-facing behaviour through the VIP (192.168.2.23), from a LAN host.**
+
+    plex.home.keithjackson.dev   -> 192.168.2.20      split-horizon intact
+    home.keithjackson.dev        -> 192.168.2.20
+    unifi.home.keithjackson.dev  -> 192.168.2.21
+    google.com                   -> 142.250.115.102   recursion to 8.8.8.8 works
+    doubleclick.net              -> 0.0.0.0           blocking LIVE in FTL, not just in the DB
+    googleadservices.com         -> 0.0.0.0
+    12 consecutive queries       -> 12/12 answered
+
+**THE FAILOVER DRILL — observed by the operator, 2026-10-04.** A single StatefulSet replica was
+deleted. It was recreated in **~30 seconds**, and **DNS never dropped a request** throughout. This is
+the first direct evidence that the replica count delivers what it was added for, rather than merely
+rendering correctly.
+
+**The SLI is not inert, and re-deriving it mattered.** Measured in Prometheus:
+`kube_statefulset_status_replicas_ready{namespace="pihole", statefulset="pihole"}` returns **1 series,
+value 2**; `kube_deployment_status_replicas_available{namespace="pihole"}` now returns **0 series**;
+and Prometheus has `pihole-down` loaded as `state=inactive health=ok` with the StatefulSet expression.
+Had the rule stayed Deployment-shaped, its `or absent(...)` branch would have matched the now-absent
+series and **fired permanently** — a standing false page rather than silence. That is the concrete
+payoff of defaulting `livenessWorkload.kind` from the rendered kind.
+
+## What I did NOT verify
+
+- **NODE failure, as opposed to pod failure.** The drill deleted a pod, which does not exercise the
+  `tolerationSeconds: 300` path at all — that timer only applies when a node goes NotReady. The
+  mechanism protecting DNS is the same one just proven (the surviving replica plus
+  `externalTrafficPolicy: Cluster` on the DNS LoadBalancers), so user-visible impact should likewise be
+  nil; what the 300 s still delays is the *replacement* replica, and during that window there is no
+  redundancy left. Untested. Pulling power from a node is the only real test.
+- **DNS during the cutover itself.** I was not sampling resolution while #45 reconciled, so whether
+  there was a brief gap between the Deployment being pruned and the StatefulSet becoming Ready is
+  **unmeasured**. The drill above covers the steady-state failover case, not that one-off transition.
+- **Two-node loss.** The hard anti-affinity means `replicas: 2` needs two schedulable nodes; losing
+  two would leave a replica `Pending` and, with `wait: true`, stall the app tier. Reasoned, not
+  exercised — and it coincides with etcd quorum loss on a 3-node control plane.
+- **Longhorn capacity headroom.** Two 2Gi claims at 3 replicas each is ~12Gi where there was ~6Gi.
+  Both claims are `Bound` and healthy; free space was not checked.
+- **Query history is now split per replica** and the admin UI shows only whichever pod answered.
+  Adlists and password are identical, so blocking and auth are consistent; the *reporting* is not, and
+  whether that is acceptable long-term is the operator's call.
+- **The residual risk is unchanged, and it is the larger one.** Replicas address node failure. LAN DNS
+  still depends on the cluster — etcd quorum, Cilium, Longhorn, a bad reconcile — and only a resolver
+  outside the cluster carrying the same `address=` lines removes that dependency. Considered and not
+  chosen (operator decision, 2026-10-04).
+- **Plex remote access (#43) is NOT covered by this entry.** Its two manual steps (the WAN tcp/32400
+  forward and Plex's "manually specify public port") and the outside-in path remain as
+  `decisions/2026-10-03-plex-remote-access-l4.md` describes them. The operator reported it working;
+  I have not measured it from off-LAN.
+- **`--emit-waves` drift is still open.** Re-running it still wants to onboard `vm-demo.yaml` and
+  `keycloak.yaml`, both listed as intentionally not onboarded in `ci/render-golden.sh`. Unfixed; see
+  `decisions/2026-10-03-plex-remote-access-l4.md`.