Website monitoring and HTTPS checks

1. What to monitor? #

Four complementary angles.

Angles #

2. HTTPS monitoring with Prometheus #

Open source and simple.

Blackbox Exporter #

# blackbox.yml
modules:
  https_2xx:
    prober: http
    timeout: 10s
    http:
      valid_status_codes: [200]
      fail_if_not_ssl: true
      preferred_ip_protocol: ip4

# prometheus.yml
scrape_configs:
  - job_name: site
    metrics_path: /probe
    params: { module: [https_2xx] }
    static_configs: [ { targets: [ "https://www.example.com", "https://shop.example.com" ] } ]
    relabel_configs:
      - { source_labels: [__address__], target_label: __param_target }
      - { source_labels: [__param_target], target_label: instance }
      - { target_label: __address__, replacement: blackbox:9115 }

# Alertes
probe_success == 0                                                   # site injoignable
(probe_ssl_earliest_cert_expiry - time()) / 86400 < 14               # certificat expirant sous 14 jours
histogram_quantile(0.95, rate(probe_duration_seconds_bucket[5m])) > 2

Good practice: Probe from at least two locations and alert when several fail: a local network outage should not wake up on-call.

3. Going further #

Journeys and real experience.

Journeys and RUM #

• Journey tests (login, cart) with Grafana k6 in browser mode, scheduled or in CI.
• RUM with Grafana Faro for real Core Web Vitals per page, browser and country.
• A public status page fed by the same probes.
• Correlation: a failing probe should lead to the backend's logs and traces.