Prometheus

• What it is: Open-source monitoring and alerting tool.
• What it does: Collects metrics (numeric data) from your apps & infrastructure (CPU, memory, requests/sec, DB latency, etc.).

• How it works:

  • Apps expose metrics in a special format (HTTP endpoint like /metrics).
  • Prometheus scrapes this data at intervals.
  • Stores it in a time-series database (values with timestamps).
• Extras: Has its own query language (PromQL). Often paired with Grafana for visualization.

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Grafana

• What it is: Open-source visualization & dashboarding tool.
• What it does: Shows data from different sources (Prometheus, Elasticsearch, MySQL, InfluxDB, etc.) in charts, graphs, and dashboards.
• Why use it: Helps you see system health, business KPIs, or infra metrics in real time.
• Extras: Can set up alerts (e.g., if CPU > 90%, send Slack/Email).

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How they work together

• Prometheus = collects & stores metrics.
• Grafana = visualizes those metrics in dashboards.

👉 Example:

1. Prometheus scrapes http_requests_total from your app.
2. Grafana shows a live graph of requests per second.
3. If it spikes abnormally, Grafana alerts you.

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⚡ So in short:

• Prometheus → Monitoring & Metrics collection
• Grafana → Visualization & Dashboards

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