Alerts Overview¶

2025-12-172025-12-17

🚨 Prometheus Alerting for MongoDB & Custom Resources¶

This page provides examples and references for Prometheus alerting rules, including MongoDB monitoring and custom container CPU usage alerts.

📚 Reference: Awesome Prometheus Alerts¶

For a comprehensive list of Prometheus alerting rules, visit the Awesome Prometheus Alerts - MongoDB Section.

🛡️ MongoDB Down Alert¶

The following Prometheus rule triggers a critical alert when a MongoDB instance is detected as down.

{
  "alert": "MongodbDown",
  "expr": "mongodb_up == 0",
  "for": "0m",
  "labels": {
    "severity": "critical"
  },
  "annotations": {
    "summary": "MongoDB Down {{ $labels.instance }}",
    "description": "MongoDB instance is down {{ $value }}"
  }
}

MongoDB Availability

This alert fires immediately when the mongodb_up metric equals zero, indicating the MongoDB instance is unreachable.

⚡ Custom Container CPU Usage Alert¶

The following custom PrometheusRule monitors CPU usage for containers named stress and triggers a warning if usage exceeds 75% of the requested CPU for more than 1 minute.

apiVersion: monitoring.coreos.com/v1
kind: PrometheusRule
metadata:
  name: container-cpu-alert
  labels:
    prometheus: kube-prometheus
    role: alert-rules
spec:
  groups:
    - name: container-cpu-usage
      rules:
        - alert: KubeContainerCPURequestAlert
          expr: |
            (rate(container_cpu_usage_seconds_total{container="stress"}[5m]) /
            on (container) kube_pod_container_resource_requests{resource="cpu", container="stress"}) > 0.75
          for: 1m
          labels:
            severity: warning
          annotations:
            summary: "Container CPU usage is above 75% of request for 5 minutes"
            description: "The container is using more than 75% of its requested CPU for 5 minutes."

CPU Usage Monitoring

Adjust the container name and threshold values as needed for your environment.
This alert helps identify containers that may be under resource pressure.