jakman85andClaude Opus 5
8e017fad91
main became a protected branch on 2026-09-29, so the direct push that 37 of 39 runbooks instructed is REJECTED. The wording was merely stale before; it is now actively wrong, and it is the line an operator reads mid-incident. Every occurrence now describes the real path: push a branch, open a PR, merge once the gate is green -- that merge is the deploy. 35 files shared one identical block; flux-reconcile.md, README.md and plex-claim.md each said it their own way and were corrected individually. plex-claim.md is rewritten around the delivery loop and records that THE SERVER IS NOW CLAIMED (PlexOnlineToken present in /config), so PLEX_CLAIM is a permanent no-op and the page only applies after a /config wipe. Adds infra/plex/claim-ship.sh, which drives branch -> commit -> push -> PR -> gate -> merge -> reconcile -> pod roll -> verdict with a stopwatch. Three steps are easy to lose under time pressure and two are SILENT when skipped: --with-source (without it the Kustomization applies the previously-fetched revision), the mandatory rollout restart (only the ciphertext changes, so the pod template is byte-identical and nothing restarts itself), and the feat/ branch prefix (act_runner capacity is 1, and a prefix inside gate.yml's push trigger fires a redundant run that serialises ahead of the PR run). Drops the "~4-minute TTL" the page asserted in four places. It was uncited, and upstream pms-docker documents no expiry at all. The countdown on plex.tv/claim is the authority. Measured loop: ~2m45s. DECISIONS-LOG carries the PM handoff: both halves of the 2026-08-31 CI claim were false, the stale-.runner root cause, the four-deep Flux dependency cascade, and the correction that a skipped Gitea job reports success rather than hanging. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
128 lines
6.4 KiB
Markdown
128 lines
6.4 KiB
Markdown
# node-cpu — CPU pressure or run-queue depth high on a node
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**Alerts:** `NodeCPUPressureHigh` (warning, 15m) and `NodeCPULoadHigh` (warning, 15m)
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**File:** `platform/monitoring/alerts.yaml`, group `platform-health.nodes`
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**Expressions:**
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`rate(node_pressure_cpu_waiting_seconds_total[5m]) > 0.15`
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`node_load5 / count without (cpu, mode) (node_cpu_seconds_total{mode="idle"}) > 1`
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## What this means here
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`NodeCPUPressureHigh` is PSI "some" for CPU: the fraction of wall-clock time during which at least
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one task was stalled waiting for a CPU. Under 5% is healthy. Averaged CPU% — what `kubectl top`
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shows — **hides this entirely**, which is why the alert uses PSI: it is the metric that surfaces the
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"spikes cause blips of delay" symptom operators actually notice.
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`NodeCPULoadHigh` is 5-minute load average divided by core count. Sustained above 1 means the run
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queue is longer than the number of CPUs.
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**Read them together.** CPU-PSI high *and* load high = genuine CPU contention. Load high *and* CPU-PSI
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normal = the queue is full of tasks blocked on **I/O**, not CPU — go to `/runbooks/node-io`, which on
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this cluster is the more dangerous of the two (etcd WAL and Longhorn replicas share one partition).
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Measured history: steady CPU PSI ran **15–23%** with load at or above core count, which is what drove
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the node resize from **6 to 8 vCPU**; afterwards PSI measured ~4.5–7.7%. So 0.15 is not an arbitrary
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threshold, it is the level the cluster actually lived at before the resize.
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## Running the commands in this runbook
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`kubectl` does not work on the operator workstation. The toolchain lives only in the pinned dev
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container, and the host's `k3s-oidc` context hangs on a browser prompt once its token expires —
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that hang is not the cluster being down. Every command below runs as:
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infra/devcontainer/dev.sh run bash -c 'kubectl --context k3s-prod get nodes'
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Always pass `--context k3s-prod` explicitly. `dev.sh` merges BOTH clusters into one kubeconfig and
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picks a current-context per invocation, and **that default has already changed once** — it was k3s-dev
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until dev was decommissioned on 2026-09-13, and is k3s-prod now. A command that names its context means
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the same thing next month as it does today; one that relies on the default does not, and the failure is
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silent (it answers confidently about the other cluster). `CLUSTER=prod infra/devcontainer/dev.sh run
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kubectl ...` selects it explicitly, and every invocation prints a banner naming the cluster it is about
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to talk to — read it. Do not run two `dev.sh` invocations at once; they share one container and
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interfere.
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USE FULLY-QUALIFIED RESOURCE NAMES, ALWAYS. Three CRDs on this cluster register the kind `Backup`:
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`longhorn.io/v1beta2`, `postgresql.cnpg.io/v1` and `velero.io/v1`. The bare short name resolves to
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Longhorn's, which holds zero objects — so `kubectl get backup -A` prints **"No resources found"** on
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a cluster holding 6 Velero backups and 27 CNPG backups. Verified on prod 2026-09-13. Reading that as
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"the backups are gone" and acting on it turns a false negative into real data loss. Write
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`backups.velero.io`, `backups.postgresql.cnpg.io`, `clusters.postgresql.cnpg.io`,
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`settings.longhorn.io`, `volumes.longhorn.io`, `nodes.longhorn.io`.
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Mutating kubectl (`apply`, `patch`, `annotate`, `rollout`) and `flux reconcile` are blocked for
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agents here: every durable change goes through git. **`main` is a protected branch — a direct push
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is rejected.** A change lands by pushing a branch, opening a PR, and merging it once the gate is
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green; that merge is the deploy. Where this runbook gives a mutating command it is for an operator,
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and it says so.
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## First commands
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Distinguish CPU contention from I/O contention — do this first:
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```
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ssh k3s-prod-1 'cat /proc/pressure/cpu; echo; cat /proc/pressure/io; echo; uptime; nproc'
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```
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Who is burning it:
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```
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infra/devcontainer/dev.sh run bash -c \
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'kubectl --context k3s-prod top nodes; echo; kubectl --context k3s-prod top pods -A --sort-by=cpu | head -20'
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```
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```
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ssh k3s-prod-1 'top -b -n1 | head -20'
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```
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Are there VMs, and are any of them emulated (the worst case)?
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```
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infra/devcontainer/dev.sh run bash -c \
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'kubectl --context k3s-prod get vmi -A -o wide'
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```
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```
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ssh k3s-prod-1 'grep -c -E "vmx|svm" /proc/cpuinfo; ls -l /dev/kvm'
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```
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## Likely causes, most likely first
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### 1. It is actually I/O, not CPU
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Most common misread. A node blocked on disk has a long run queue and normal CPU-PSI. Confirm with
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`/proc/pressure/io` and go to `/runbooks/node-io`. On 2026-09-07 the node that died had I/O-PSI full
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at 11.36 while CPU looked unremarkable.
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### 2. A KubeVirt VM running under TCG emulation
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`useEmulation: true` **silently forces TCG on KubeVirt v1.9** — it is set to `false` on purpose. A VM
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that lost `/dev/kvm` or was authored with emulation burns a whole core per vCPU. Heavy sustained TCG
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load has also degraded the Cilium datapath into intermittent LB-VIP unreachability (cleared by a
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restart), so an "intermittent networking" report alongside this alert is probably one cause, not two.
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Check `grep -c -E "vmx|svm" /proc/cpuinfo` (nested KVM is verified working; Proxmox nodes use
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`cpu_type=host`).
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### 3. A Longhorn rebuild's checksumming
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Rebuilds are I/O-heavy but not free on CPU. Same remediation as `/runbooks/longhorn-degraded`: freeze
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with `concurrent-replica-rebuild-per-node-limit` `0`, thaw to `1`.
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### 4. Prometheus rule evaluation or a Loki query
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`PersistentVolumeFillingUpPredicted` runs `predict_linear` over a 24h window across every PVC; a
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Grafana panel doing the same interactively is heavier still. Bursty, self-limiting, usually harmless.
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### 5. Genuine capacity
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If nothing is anomalous the node is simply undersized again. The 6 → 8 vCPU resize is the precedent.
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A bpg cores change **reboots the VM**, so roll **one node at a time, waiting for Longhorn
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`robustness=healthy` between each**.
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## When to escalate or stop
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- **If I/O-PSI is also elevated, stop treating this as a CPU problem** and switch to
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`/runbooks/node-io`. Wrong runbook is the main risk here.
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- Alone and steady, this alert is a capacity signal — schedule it, do not page on it. That is why it
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is a warning with a 15m `for`.
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- **Do not drain or cordon** to shed CPU load; this cluster does not drain.
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- Escalate to the operator for a vCPU change (it reboots the node) or to kill a VM you did not create.
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---
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Source of truth: `runbooks/node-cpu.md`. Index: `/runbooks/`
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Records: `DECISIONS-LOG.md` (node vCPU 6→8 and the post-resize PSI measurements; KubeVirt
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`useEmulation` finding).
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