Agent-Skills.md

Agent Skills: Cluster Health Check

Scan cluster health — Flux kustomizations, pod status, recurring crashes, node conditions, active Alertmanager alerts, CNPG databases, certificate expiry — and output an actionable summary with fix plan. Use when user asks "how's the cluster", "cluster health", "what's broken", "check the cluster", or similar.

UncategorizedID: agentydragon/ducktape/cluster_health

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agentydragon/ducktape
agentydragon
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Install this agent skill to your local

pnpm dlx add-skill https://github.com/agentydragon/ducktape/tree/HEAD/cluster/skills/cluster_health

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cluster/skills/cluster_health/SKILL.md

Skill Metadata

Name
cluster_health
Description
Scan cluster health — Flux kustomizations, pod status, recurring crashes, node conditions, active Alertmanager alerts, CNPG databases, certificate expiry — and output an actionable summary with fix plan. Use when user asks "how's the cluster", "cluster health", "what's broken", "check the cluster", or similar.

Cluster Health Check

Comprehensive cluster health scan. Collect results from all checks, then produce a single structured report with an actionable fix plan.

Use the kubectl-local MCP server tools for all read queries — the SA has a cluster-diagnostics-reader ClusterRole with cluster-wide read access to nodes, pods, deployments, Flux kustomizations, HelmReleases, cert-manager, CNPG, metrics, Gateway API, Kyverno, and more (see <cluster/k8s/agents/agent-rbac-base/clusterrole-cluster-diagnostics-reader.yaml>). It can also patch Flux Kustomizations (for manual reconciliation triggers).

Fall back to Bash(kubectl ...) with dangerouslyDisableSandbox: true only for operations the SA cannot do (e.g., writing resources outside claude-sandbox, reading pod logs in namespaces without explicit rolebindings).

What to Check

Run checks in parallel where possible.

Flux GitOps

  • All Flux Kustomizations — ready status, suspended, stalled
  • HelmReleases — ready status, failed upgrades
  • Terraform resources (tofu-controller) — ready and applied status
  • Identify suspended kustomizations and cross-reference with cluster/docs/plan.md "Suspended Kustomizations" to distinguish expected vs unexpected suspensions

Alertmanager & Prometheus Alerts

  • Alertmanager deployment health — Alertmanager CRs, pods, endpoints, and API status in monitoring
  • Active firing Alertmanager alerts from the live API, not just PrometheusRule definitions. Query Alertmanager API v2 for active alerts and preserve the identifying labels (alertname, severity, namespace, pod, job, service), startsAt, generatorURL, and annotations.
  • Separately note silenced or inhibited alerts if they explain why a firing condition is not paging. Do not treat silenced maintenance alerts as healthy without checking the silence reason, creator, matcher, and expiry.

Prefer kubectl-local for Kubernetes object reads. For the live Alertmanager API, use the least-invasive available path: Kubernetes service proxy if exposed by the MCP server, otherwise the Bash(kubectl ...) escape hatch outside the sandbox for a short kubectl port-forward or an ephemeral curl pod in claude-sandbox. The in-cluster service is typically http://monitoring-alertmanager.monitoring.svc.cluster.local:9093; query /api/v2/status, /api/v2/alerts?active=true, and /api/v2/silences.

Pod & Workload Health

  • Non-running pods (Pending, CrashLoopBackOff, ImagePullBackOff, Error, etc.)
  • Flapping pods — containers with restart counts >3 where restarts are recent
  • Recent OOMKill and Eviction events
  • Failed jobs

Important: When checking restart counts, always check if restarts are recent. The kubectl get pods output shows restart count AND time since last restart, e.g. 1256 (41h ago). A high total count accumulated over many days means nothing if the last restart was days ago. Focus on pods where restarts are happening now (last restart within the last hour or so). Check the pod's AGE and the "(Xh ago)" suffix to determine recency.

Node Health

  • Node conditions: Ready, MemoryPressure, DiskPressure, PIDPressure
  • Resource usage (kubectl top nodes)
  • If any node is under pressure or >80% memory/disk usage: break down the top pod consumers on that node to identify what's causing the pressure
  • Active taints on all nodes (cordoned, NoSchedule, NoExecute, etc.)

Databases & Certificates

  • CNPG cluster health — instance count vs ready count, phase
  • cert-manager certificates — ready status, approaching expiry
  • Stuck ACME challenges

Warning Events

  • Recent Warning-type events, focusing on recurring patterns (high event counts)

Investigation

When any check reveals an error (unhealthy CNPG cluster, CrashLoopBackOff pod, failed HelmRelease, stuck Terraform, etc.), don't just report the status — dig into the cause before moving on:

  • Pod failures: check logs, previous container logs (--previous), describe output (events, conditions, scheduling failures)
  • CNPG issues: check operator logs in cnpg-system, individual instance logs, cluster events
  • Flux/Helm failures: check the controller logs, the kustomization/helmrelease events
  • Alertmanager alerts: trace each firing alert to the owning PrometheusRule and underlying Kubernetes object; use generatorURL or Prometheus/Mimir queries when needed, then classify it as active breakage, stale/wedged alert state, expected maintenance, or already-resolved-but-not-yet-cleared
  • Node problems: check node describe, kubelet conditions, recent events on the node
  • Image pull failures: check if the registry (Harbor) is up, if the image tag exists, if pull secrets are configured

Include the root cause (or best hypothesis) in the report, not just "pod is failing."

Image Pull Failures

When images fail to pull, trace the full pipeline:

  • Check if the image exists in Harbor (registry.allegedly.works)
  • Check if the CI build that produces the image succeeded — look at GitHub Actions workflows (gh run list), BuildBuddy invocations, or the relevant buildbuddy.yaml / .github/workflows/ pipeline
  • Check if the image push step succeeded (GitHub Actions logs, Harbor push events)
  • Report where the pipeline broke (build failed, push failed, tag missing, auth issue)

Anomaly Detection

Flag anything that looks out of place:

  • Pods running in namespaces that should be empty (suspended services with leftover workloads not cleaned up)
  • Stale errored/completed objects: failed Jobs not cleaned up, old ReplicaSets with no pods, orphaned PVCs for deleted workloads
  • Resources that exist in the cluster but have no corresponding Flux kustomization managing them (drift from GitOps)
  • Pods/deployments with no owner (not managed by a Deployment/StatefulSet/DaemonSet/Job)

Report Format

After collecting all data, produce:

# Cluster Health Report — <date>

## Summary

<one-line assessment: healthy / degraded / critical>
<count of issues by severity>

## Critical Issues

<broken kustomizations, CrashLoopBackOff pods, NotReady nodes, unhealthy CNPG
clusters, active high-severity Alertmanager alerts, expired certificates — each
with: what, impact, evidence, fix>

## Warnings

<high restart counts, unexpected suspensions,
active low-severity Alertmanager alerts, resource pressure approaching limits>

## Expected / Known

<intentional suspensions per plan.md, scaled-to-zero deployments, offline
roaming nodes>

## Fix Plan

<ordered actions to resolve critical + warnings, prioritized by impact and
dependency order>

Cross-Reference

Check findings against:

  • cluster/docs/plan.md "Suspended Kustomizations" — don't flag expected suspensions
  • cluster/docs/plan.md "Next Actions" — note if findings match known TODOs
  • cluster/docs/troubleshooting.md — reference known fix procedures for matching symptoms