Prometheus is an open-source monitoring and alerting toolkit that was originally built at SoundCloud. Think of it as your application’s heartbeat monitor — constantly watching, collecting, and helping you understand what’s going on.

🧠 Why Prometheus?

Imagine you’re running an application with hundreds of containers across multiple environments. How do you know if something’s slow or broken? Prometheus answers that by:

  • Scraping metrics from your apps and infrastructure
  • Storing data efficiently using a time-series database
  • Letting you query metrics with a powerful language (PromQL)
  • Alerting you when things go wrong

🔧 How It Works

Prometheus works by pulling metrics from exporters (tiny HTTP servers that expose /metrics). For example:

curl http://localhost:9090/metrics

This returns a bunch of useful metrics in plain text format.

🚨 Alerts

Prometheus integrates with Alertmanager to send alerts via email, Slack, or PagerDuty. Example alert rule:

groups:
- name: instance-down
  rules:
  - alert: InstanceDown
    expr: up == 0
    for: 1m
    labels:
      severity: critical
    annotations:
      summary: "Instance { $labels.instance } is down"

📊 Visualization

Although Prometheus has a built-in UI, most people use it with Grafana for dashboards.

🐳 Running with Docker

docker run -d -p 9090:9090 prom/prometheus

🌐 Common Use Cases

  • Kubernetes cluster monitoring
  • App performance analysis
  • Infrastructure health tracking

🏁 Summary

Prometheus is your go-to solution for modern monitoring. It’s flexible, scalable, and built for the cloud-native era. If you’re working with Kubernetes — you’ll definitely meet Prometheus.

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