groups:
  - name: webapp
    rules:
      - alert: WebappDown
        expr: up{job="webapp"} == 0
        for: 30s
        labels:
          severity: critical
        annotations:
          summary: "Webapp is down"
          description: "Prometheus cannot scrape the webapp for more than 30 seconds."

      - alert: HighErrorRate
        expr: sum(rate(http_requests_total{status=~"5.."}[1m])) / sum(rate(http_requests_total[1m])) > 0.05
        for: 1m
        labels:
          severity: warning
        annotations:
          summary: "More than 5% of requests are failing"
          description: "The 5xx ratio has been above 5% for 1 minute."

      - alert: HighLatencyP95
        expr: histogram_quantile(0.95, sum by (le) (rate(http_request_duration_seconds_bucket[5m]))) > 0.5
        for: 2m
        labels:
          severity: warning
        annotations:
          summary: "p95 latency above 500ms"
          description: "95% of requests take longer than 0.5s."