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jakman85andClaude Opus 5 4687521d65 fix(monitoring): delete the Longhorn rule that measured allocation and called it capacity

LonghornVolumeCapacityHigh went pending within minutes of the Longhorn scrape
landing today. Re-measured on prod: it read 0.9731 on the Prometheus TSDB volume
(actual_size 52243681280 / capacity 53687091200) while the kubelet reported the
SAME filesystem 20.8% used. actual_size is head + pinned snapshots, and one
user_created=false system snapshot from prod-1's replica rebuild holds 40510484480
bytes (37.7 GiB) of it; Longhorn returns no freed blocks without discard/TRIM, and
retentionSize 45GiB on a 50Gi volume targets 90% by design. The ratio is pinned
near 1.0 and cannot fall back under 0.85 — a permanently-firing alert, the same
shape as CNPGNoRecoverabilityPoint.

DELETED, not re-thresholded. Raising the threshold would tune away a true
statement about allocation. Redundancy proven, not asserted: of 24 Longhorn
volumes on prod, 23 appear in kubelet_volume_stats_inodes > 0 and so fall inside
MonitoringVolumeFillingUp (namespace="monitoring") or PersistentVolumeFillingUp /
PersistentVolumeAlmostFull. The 24th is unifi/unifi-rootdisk, volumeMode Block —
no filesystem for anyone to measure, and the deleted rule was not covering it
either.

AND A SECOND INERTNESS the scrape did not fix. longhorn_volume_robustness on
longhorn 1.12.1 is one-hot over a `state` label with values 0/1, not the 0-3 enum
the rules assumed:
  count(longhorn_volume_robustness)                  => 96  (24 volumes x 4 states)
  count by (state) (longhorn_volume_robustness == 1) => {state="healthy"} 24
  count(longhorn_volume_robustness == 2)             => (empty)
  count(longhorn_volume_robustness == 3)             => (empty)
So a FAULTED volume would still have alerted nobody. Re-keyed to the label; the
"44 series / 72 unknown(0, detached)" note in platform/longhorn/helmrelease.yaml
was the same misreading and is corrected in place.

The allocation question moved to where allocation is a budget. LonghornNodeStorageHigh
fired at 0.85, but storage-minimal-available-percentage is 25 on this cluster, so a
disk leaves the scheduling pool at 75% used — the old threshold could only fire
after scheduling had already been refused. Replaced by:
  LonghornDiskAllocationHigh  (longhorn_disk_usage_bytes / longhorn_disk_capacity_bytes) > 0.70, 30m
  LonghornDiskUnschedulable   longhorn_disk_status{condition="schedulable"} == 0, 15m
Per DISK, not per node: longhorn_node_storage_usage_bytes sums a node's disks, so
one full disk could hide behind a half-empty sibling. Measured prod usage
0.2254 / 0.2306 / 0.2369 on prod-1/2/3.

PROVEN NEITHER PERMANENTLY FIRING NOR INERT. platform/monitoring/tests/longhorn.test.yaml
adds 6 cases pinning every rule quiet on today's measured prod state and firing on
a constructed bad state, with every `for:` asserted, plus regression assertions that
the old `== 2`/`== 3` forms match nothing and that per-disk 0.72 is visible where the
node-summed 0.475 is not. Mutation-checked 11 ways; each turns the suite RED. Live on
prod: all four new expressions return empty, while the sum of their selector
cardinalities is 54. The L0 UNTESTED_ALERTS register shrinks by seven (7/56 -> 14/58
alert rules unit-tested), which also brings MonitoringVolumeFillingUp,
PersistentVolumeFillingUp and PersistentVolumeAlmostFull under test since the
redundancy claim rests on them.

REPORTED, NOT CHANGED (DECISIONS-LOG, owner decisions): retentionSize 45GiB on a
50Gi volume is too tight — recommend 36GiB, with reasoning; and discard/TRIM on the
longhorn StorageClass is feasible but not advisable now — remove-snapshots-during-
filesystem-trim reads false on prod, so trim would not have reclaimed the 37.7 GiB
anyway, and continuous discard on nodes where the etcd WAL shares the spindle points
at this cluster's known failure mode.

Co-Authored-By: Claude Opus 5 <[email protected]>

2026-09-13 17:19:03 -05:00

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Alert runbooks — home-network-k3s prod

This is the index page served at https://home.keithjackson.dev/runbooks/.

Every alert rule in this platform carries an annotation of the form

runbook_url: "https://${BASE_DOMAIN}/runbooks/<name>"

46 of them, over the 35 names below. Until this directory existed, that path returned HTTP 404 on the live cluster: every alert that reached a human handed them a dead link at the exact moment they needed help. These pages are what makes the link resolve.

How to run the commands in these runbooks

kubectl does not work on the operator workstation. The toolchain lives only in the pinned dev container, and the host's k3s-oidc context hangs on a browser prompt once its token expires — that hang is not the cluster being down.

infra/devcontainer/dev.sh run bash -c 'kubectl --context k3s-prod get nodes'

Always pass --context k3s-prod. dev.sh merges BOTH clusters into one kubeconfig and picks a current-context per invocation, and that default has already changed once — k3s-dev until dev was decommissioned on 2026-09-13, k3s-prod now. A command that names its context still means the same thing next month; one that relies on the default does not, and the failure is silent. CLUSTER=prod infra/devcontainer/dev.sh run kubectl ... selects it explicitly, and every invocation prints a banner naming the cluster — read it. Do not run two dev.sh invocations at once; they share one container.

Use fully-qualified resource names, always. Three CRDs on this cluster register the kind Backup — longhorn.io/v1beta2, postgresql.cnpg.io/v1, velero.io/v1 — and the bare short name resolves to Longhorn's, which holds zero objects. kubectl get backup -A therefore prints "No resources found" on a cluster holding 6 Velero and 27 CNPG backups (verified on prod 2026-09-13). Acting on that false negative is how a CLI quirk becomes real data loss. Write backups.velero.io, backups.postgresql.cnpg.io, clusters.postgresql.cnpg.io, settings.longhorn.io, volumes.longhorn.io, nodes.longhorn.io.

git push origin main is the deploy; there is no other apply step. Durable changes go through git.

Alerts you should not trust the silence of (measured 2026-09-13)

The Longhorn and cert-manager scrapes were ENABLED on 2026-09-13, so the Longhorn row below is no longer inert — and re-keying the two robustness rules the same day fixed a SECOND inertness the scrape had left in place (the metric is one-hot over a state label, not a 0–3 enum). Take the Longhorn row as history; the rest of this table still holds, and Flux-controller and Hubble/Cilium rule groups still evaluate against nothing and cannot fire:

Missing scrape job	Inert alerts
Longhorn	`LonghornVolumeDegraded`, `LonghornVolumeFaulted`, `LonghornDiskAllocationHigh`, `LonghornDiskUnschedulable`
cert-manager	`CertificateExpiringSoon`, `CertificateExpiryImminent`, `CertificateNotReady`
Flux (`gotk_*`)	`FluxReconciliationFailure`, `FluxResourceSuspended`, `ImageUpdateAutomationFailing`, `ImagePolicyStalled`, `UpdateHealthGateFailed`
Hubble (`hubble_drop_total`)	`HubbleDeniedFlowSpike`
etcd (`kubeEtcd` disabled for k3s, deliberately)	no etcd fsync alerting exists at all

Each affected runbook says so on its own page and gives the by-hand equivalent. See targets-down.

The runbooks

Nodes

node-down — a node's node-exporter is unscrapable; the node may be gone, or its kubelet may have stopped posting status while the host stays up (the 2026-09-07 shape).
node-io — disk I/O pressure/starvation. The etcd WAL shares a partition with Longhorn replicas; this is the alert that would have called the 2026-09-07 outage and did not exist at the time.
node-memory — memory pressure. Includes why SwapTotal == 0 is not evidence swap is off.
node-disk — a node filesystem filling up. /data is the one that matters.
node-cpu — CPU PSI and run-queue depth, and how to tell CPU contention from I/O contention.

Storage

longhorn-degraded — a volume has lost redundancy. Normal after any reboot, and the rebuild is the expensive part. Freeze/thaw commands here.
longhorn-faulted — no usable replica. Data at risk; stop before anything destructive.
longhorn-capacity — a node's Longhorn disk running out of room for replicas (allocation, not PVC fill; for PVC fill see pvc-capacity / monitoring-capacity).
pvc-capacity — PVC filling up / almost full / predicted to fill. These rules work.
monitoring-capacity — Prometheus or Loki running out of disk; don't let the monitor blind itself.

GitOps and updates

flux-reconcile — a Flux resource stuck at Ready=False. Which tier decides the blast radius.
flux-suspended — reconciliation turned off and forgotten. Drift becomes silent.
update-rollback — a HelmRelease failed its health gate and is rolling back.
image-automation — the git write-back engine is failing (feature is disabled here).
image-policy-stalled — an ImagePolicy/ImageRepository cannot resolve a tag.

Certificates

cert-issuance — ACME issuance failing. The DNS-01 self-check is the usual cause.
cert-expiry — a certificate is expiring. Almost always a late symptom of cert-issuance.

Networking

vpn-down — the egress VPN tunnel. Includes the silent egress-gateway staleness that this alert cannot see, and what the kill-switch actually does.
denied-flows — policy-denied flow spike. The Cilium hairpin/identity regression class.

Backups and DR

backup-failure — a Velero backup failed. The R2 object-tagging incompatibility is documented here.
backup-partial — a Velero backup completed with partial failures, and which skips are deliberate.
backup-missed — no successful Velero backup in 24h.
cnpg-archiving — WAL archiving stuck / no recoverability point. An availability incident, not just a backup one.
cnpg-backup-missed — no recent CNPG base backup. Velero does not cover these databases.
cnpg-wal-growth — pg_wal not being recycled. Never delete WAL by hand.
cnpg-exporter — the CNPG SQL exporter erroring: a blind spot that looks exactly like health.
cnpg-primary-spread — two or more CNPG primaries on one node. Blast radius, not an outage, and the rebalance costs ~9s of writes per database — one cluster at a time.

Identity

keycloak-down — the IdP is down. Blast radius, and the break-glass path that still works.
keycloak-db — Keycloak's CloudNativePG database is unavailable.
keycloak-client-secrets — the client/URL reconciler failing or silent. The 2026-09-06 lockout that every green signal missed.

Virtualisation

kubevirt-control-plane — VM lifecycle operations will fail; running VMs keep running.
kubevirt-launch-failed — a VMI reached the Failed phase. The three k3s-specific launch traps.
kubevirt-crashloop — a virt-launcher pod restarting repeatedly.
cdi-import-stuck — a DataVolume import not progressing. Check node I/O before restarting it.

Editing a runbook

Each page is runbooks/<name>.md in the home-network-k3s-impl repo. Edit it, push to main, and Flux re-renders the ConfigMap and rolls the two-replica server; kustomize's content hash on the generated ConfigMap name is what triggers the roll.

Adding a new alert with a runbook_url requires the matching runbooks/<name>.md and its <name>=<name>.md entry in runbooks/kustomization.yaml. Both are enforced by conformance/tests/l0-static/alert-runbooks-resolvable, which runs unconditionally in the merge gate — "the file exists in git" and "the URL resolves in the cluster" are different claims, and it checks both.

Every page must carry the four operator sections (What this means here, First commands, Likely causes, most likely first, When to escalate or stop), mention dev.sh, and pass --context k3s-prod. The check enforces that too, because a stub that makes the link resolve while helping nobody is worse than the 404 it replaced — it looks fixed.

Deliberately public. The UIs that declare forward-auth (pihole, jackett, qbittorrent, radarr, sonarr) really are closed: enforcement is per-pod, each one's HTTPRoute targeting its oauth2-proxy sidecar on :4180 rather than the app port. If these pages did too, keycloak-down would be unreadable exactly when Keycloak is down, keycloak-db unreadable when its database is down, and keycloak-client-secrets unreadable during the precise failure that broke all 12 OIDC clients on 2026-09-06 behind an entirely green cluster. An operator who cannot log in is this route's primary reader. The content is operational procedure — metric names, thresholds, kubectl invocations, topology — and no secrets. See runbooks/serving/httproute.yaml for the full reasoning, including how forward-auth is actually enforced here and the instruction to leave this route out of any Gateway-level ext-authz attachment if one is ever introduced.

The running narrative of real incidents on this cluster is DECISIONS-LOG.md.

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