home-network-k3s-impl/runbooks/cert-expiry.md

cert-expiry — A certificate is expiring soon, or imminently

Alerts: CertificateExpiringSoon (warning, <14d, 1h) and CertificateExpiryImminent (critical, <3d, 1h) File: platform/monitoring/alerts.yaml, group platform-health.certificates Expression: (certmanager_certificate_expiration_timestamp_seconds - time()) < (14 * 24 * 3600) / (3 * 24 * 3600)

What this means here

cert-manager has a Certificate whose expiry is inside 14 days (warning) or 3 days (critical) and it has not renewed. cert-manager normally renews at two-thirds of lifetime — about 60 days into a 90-day Let's Encrypt certificate — so by the time this fires, renewal has already been failing for weeks. Treat it as a late symptom of /runbooks/cert-issuance, not as a separate problem: the fix is almost always "why is issuance failing", and expiry is the clock running out on that.

What is at stake concretely. There is effectively one certificate that matters: wildcard-home in the gateway namespace, secret wildcard-home-tls, requesting both *.${BASE_DOMAIN} and ${BASE_DOMAIN} from ${ACME_CLUSTER_ISSUER} (= letsencrypt-prod on prod). Every HTTPS listener on the shared Gateway terminates with it — the wildcard https listener and the https-apex listener both reference wildcard-home-tls. If it expires:

• every public hostname serves an untrusted certificate;
• SSO breaks in-cluster, because OIDC clients validate the issuer's TLS. This is not hypothetical: while the wildcard was still LE-staging, in-cluster clients rejected it with x509: certificate signed by unknown authority, which is what forced the move to letsencrypt-prod;
• and the page you are reading right now is served over that same certificate.

There is no history of an actual expiry on this cluster. The recorded history is all issuance failures. Say so rather than inventing precedent — but note the corollary: the renewal path has never been exercised under stress, so do not assume it will quietly work.

Verify the alert can even fire (measured 2026-09-13)

This alert is currently INERT. count(certmanager_clock_time_seconds) and count(certmanager_certificate_expiration_timestamp_seconds) both returned 0 series on prod: there is no cert-manager scrape job among Prometheus's 19 jobs, so all three certificate rules evaluate against nothing. Certificate expiry is unmonitored today. Check expiry by hand with the commands below, and see /runbooks/targets-down for the full list of inert rule groups. Adding cert-manager's ServiceMonitor is open work.

Running the commands in this runbook

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. Every command below runs as:

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

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

USE FULLY-QUALIFIED RESOURCE NAMES, ALWAYS. Three CRDs on this cluster register the kind Backup: longhorn.io/v1beta2, postgresql.cnpg.io/v1 and velero.io/v1. The bare short name resolves to Longhorn's, which holds zero objects — so kubectl get backup -A prints "No resources found" on a cluster holding 6 Velero backups and 27 CNPG backups. Verified on prod 2026-09-13. Reading that as "the backups are gone" and acting on it turns a false negative into real data loss. Write backups.velero.io, backups.postgresql.cnpg.io, clusters.postgresql.cnpg.io, settings.longhorn.io, volumes.longhorn.io, nodes.longhorn.io.

Mutating kubectl (apply, patch, annotate, rollout) and flux reconcile are blocked for agents here: every durable change goes through git (git push origin main is the deploy). Where this runbook gives a mutating command it is for an operator, and it says so.

First commands

Every certificate and its real expiry, straight from the CRs (works with no metrics):

infra/devcontainer/dev.sh run bash -c \
  'kubectl --context k3s-prod get certificates.cert-manager.io -A \
     -o custom-columns=NS:.metadata.namespace,NAME:.metadata.name,READY:.status.conditions[?\(@.type==\"Ready\"\)].status,NOTAFTER:.status.notAfter,RENEWAL:.status.renewalTime,ISSUER:.spec.issuerRef.name'

What the Gateway is actually serving (the answer that matters), read from outside the cluster with an explicit SNI — testing HTTPS from inside a pod is misleading here, and an IP+SNI probe without the right SNI returns curl exit 35:

curl -sv --resolve home.keithjackson.dev:443:192.168.2.20 https://home.keithjackson.dev/runbooks/ 2>&1 | grep -E "expire|subject|issuer|SSL certificate"

echo | openssl s_client -connect 192.168.2.20:443 -servername grafana.home.keithjackson.dev 2>/dev/null | openssl x509 -noout -subject -issuer -dates

Is a renewal in flight or stuck?

infra/devcontainer/dev.sh run bash -c \
  'kubectl --context k3s-prod get certificaterequests.cert-manager.io,orders.acme.cert-manager.io,challenges.acme.cert-manager.io -A; echo; \
   kubectl --context k3s-prod -n cert-manager logs deploy/cert-manager --tail=80 | tail -40'

Likely causes, most likely first

1. Issuance has been failing since the last successful renewal

The dominant cause, and the one with real history. Go to /runbooks/cert-issuance — it covers the DNS-01 self-check failure (fixed with dns01RecursiveNameservers: "1.1.1.1:53,8.8.8.8:53" and dns01RecursiveNameserversOnly: true), the Cloudflare token, and the ACME order/challenge chain. Fixing issuance fixes expiry; nothing else does.

2. Two clusters racing the same _acme-challenge TXT record

A specific, recorded hazard for any future two-cluster window. infra/PROD-PROVISIONING.md §10 records that after the 2026-09-04 incident, platform-config would have requested a *.home.keithjackson.dev wildcard from letsencrypt-prod for a certificate dev already held; both clusters would then have raced each other's _acme-challenge TXT records on one Cloudflare zone and neither would reliably solve DNS-01. It never fired only because the tier was suspended. If a second cluster exists, confirm which one owns the zone before renewing.

3. Let's Encrypt rate limits

One wildcard is well inside the limits, so this is unlikely — unless something has been retrying in a loop. cert-manager logs will say too many certificates already issued. Remediation: stop the loop, wait out the window; do not switch to letsencrypt-staging as a workaround, because in-cluster OIDC clients reject the staging chain (that is the bug that forced LE-prod).

4. The issuer or its credential changed

${ACME_CLUSTER_ISSUER} is a cluster-vars knob; the Cloudflare API token is a SOPS-encrypted Secret. Note the standing rule: non-secret, environment-specific values must not live inside an encrypted Secret — ${BASE_DOMAIN} substitution can never reach inside one, which is exactly how prod's OIDC clients once ended up pointed at dev's Keycloak.

5. The Certificate is Ready but the Secret is stale

Check the Secret's actual notAfter (the openssl command above) rather than the CR's status. The Gateway reads the Secret.

When to escalate or stop

• CertificateExpiryImminent on wildcard-home is a cluster-wide outage in under 3 days, including SSO and including this runbook server. Get the operator immediately.
• Do not switch to letsencrypt-staging to make issuance succeed. It will issue, and it will break every in-cluster OIDC client with x509: unknown authority.
• Do not delete the wildcard-home-tls Secret to force a reissue while issuance is broken — you would replace a certificate that still has days left with none at all.
• Do not hand-edit the Secret. cert-manager owns it; the durable change is in git.
• Verify DNS at the authority (dig @betty.ns.cloudflare.com _acme-challenge.home.keithjackson.dev TXT), never at a resolver: 1.1.1.1 has served a deleted TXT record for minutes here and produced a false failure diagnosis.

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Source of truth: runbooks/cert-expiry.md. Index: /runbooks/ Records: DECISIONS-LOG.md "Fix 5 — cert-manager DNS-01 self-check via public resolvers" and the LE-staging → LE-prod switch (Session 7); infra/PROD-PROVISIONING.md §10 (the queued ACME race).