Monitoring Domain Expiration with Prometheus, black_exporter, and Grafana

Web monitoring involves tracking specific URLs or interfaces, and this article focuses on practical monitoring of certificate expiration using Docker, Prometheus, black_exporter, and Grafana.

1. Docker installation [root@hd03]# docker run -d --restart=always --name domain_exporter -p 9222:9222 caarlos0/domain_exporter

2. Prometheus configuration Append the following job definition to prometheus.yml :

- job_name: domain
  scrape_interval: 1h
  metrics_path: /probe
  relabel_configs:
    - source_labels: [__address__]
      target_label: __param_target
    - target_label: __address__
      replacement: 192.168.18.69:9222
  static_configs:
    - targets:
      - qq.com
      - baidu.cn

After saving, reload Prometheus configuration:

[root@hd03]# curl -X POST http://localhost:9090/-/reload

3. Add domain alert rules Create prometheus/rules/domain.yml with the following alerts:

groups:
- name: domain
  rules:
  - alert: 域名检测失败
    expr: domain_probe_success == 0
    for: 2h
    labels:
      severity: warning
    annotations:
      summary: '{{ $labels.instance }}'
      description: '{{ $labels.domain }}域名检测失败'
  - alert: 域名过期
    expr: domain_expiry_days < 30
    for: 2h
    labels:
      severity: warning
    annotations:
      summary: '{{ $labels.instance }}'
      description: '{{ $labels.domain }}将在30天后过期'
  - alert: 域名过期
    expr: domain_expiry_days < 5
    for: 2h
    labels:
      severity: page
    annotations:
      summary: '{{ $labels.instance }}'
      description: '{{ $labels.domain }}将在5天后过期'

Reload Prometheus again to apply the new rules. With these configurations, Grafana can visualize the metrics and trigger alerts when a domain becomes unreachable or its certificate is about to expire.

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