prometheus-alertmanager

# Skill: Prometheus & Alertmanager > **Expertise:** PromQL, alert rules, recording rules, Alertmanager routing, inhibition, silences. ## When to load When writing alert rules, debugging PromQL, configuring Alertmanager routing, or investigating a firing alert. ## Golden Signal Alert Rules ```yaml # alerts/service-golden-signals.yaml groups: - name: service.golden-signals rules: # ── Errors ──────────────────────────────────────── - alert: HighErrorRate expr: | ( sum(rate(http_requests_total{status=~"5.."}[5m])) by (namespace, service) / sum(rate(http_requests_total[5m])) by (namespace, service) ) > 0.01 for: 2m labels: severity: critical annotations: summary: "Error rate > 1% — {{ $labels.service }} in {{ $labels.namespace }}" description: "Current error rate: {{ $value | humanizePercentage }}" runbook_url: "https://runbooks.internal/high-error-rate" # ── Latency ─────────────────────────────────────── - alert: HighP99Latency expr: | histogram_quantile(0.99, sum(rate(http_request_duration_seconds_bucket[5m])) by (namespace, service, le) ) > 1.0 for: 5m labels: severity: warning annotations: summary: "p99 latency > 1s — {{ $labels.service }}" description: "p99: {{ $value | humanizeDuration }}" runbook_url: "https...