Prometheus

What is Prometheus?

Prometheus is the standard open-source metrics and monitoring system: it scrapes metrics from configured targets on an interval, stores them as time series, and lets you query them with PromQL. It's the usual data source behind Laradock's Grafana. Laradock runs it from the official prom/prometheus image.

Start Prometheus

docker compose up -d prometheus

Stop Prometheus

docker compose stop prometheus

This stops the container without deleting its stored metrics (kept in the prometheus volume). To remove the container: docker compose rm -f prometheus.

Configuration

All settings live in prometheus/defaults.env and can be overridden by adding the same line to your own .env:

Variable	Default	What it does
PROMETHEUS_VERSION	v3.13.0	Image tag from Prometheus's Docker Hub.
PROMETHEUS_HOST_PORT	9091	Host-side port Prometheus is published on (container port 9090).

Check it's running

Open the web UI at http://localhost:9091, or check the health endpoint: curl http://localhost:9091/-/healthy.

Add scrape targets

Edit prometheus/prometheus.yml (mounted read-only into the container) to add jobs and targets, then restart:

docker compose restart prometheus

Common issues

• Port already in use on your host. Change PROMETHEUS_HOST_PORT in .env and restart: docker compose up -d prometheus.
• New scrape targets aren't picked up. Prometheus reads prometheus.yml at startup; after editing it you need docker compose restart prometheus, not just save the file.
• Data disappears after docker compose down. Metrics live in the named prometheus volume, not a bind mount. If you removed volumes (docker compose down -v), history is gone.
• Can't reach a scrape target from inside the container. Use container names (php-fpm, nginx, etc.) as targets, not localhost, Prometheus runs in its own container on the frontend/backend networks.

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Want to chart this data with dashboards? See Grafana. Need a general-purpose time-series store instead? See InfluxDB. New to Laradock? Start with Getting Started.