Skip to main content
Prometheus collects metrics by polling targets at a fixed interval. This page explains the prometheus.yml configuration used in this stack and how to extend it.

​
Full configuration

global:
  scrape_interval: 15s

scrape_configs:
  - job_name: 'node-exporter'
    static_configs:
      - targets: ['node-exporter:9100']

​
Configuration fields

​
global.scrape_interval
string
default:"15s"
How often Prometheus polls each target for metrics. A value of 15s means Prometheus sends an HTTP request to every configured target every 15 seconds and stores the returned time-series data.
​
scrape_configs
object[]
required
A list of scrape jobs. Each entry defines a named job and the targets Prometheus should poll.
​
scrape_configs[].job_name
string
required
A unique name for the scrape job. Prometheus attaches this value as the job label on every metric it collects from the targets in this job. In this stack the job is named node-exporter.
​
scrape_configs[].static_configs
object[]
required
A list of static target groups. Each group specifies one or more host:port addresses that Prometheus will scrape.
​
scrape_configs[].static_configs[].targets
string[]
required
The addresses Prometheus scrapes. The single target here is node-exporter:9100.The hostname node-exporter resolves because Docker Compose creates an internal DNS entry for every service using its service name. Prometheus and node-exporter share the same Docker network, so node-exporter:9100 reaches the exporter without exposing anything on the host network.

​
Docker Compose service

The prometheus service in docker-compose.yml is defined as follows: 
prometheus:
  image: prom/prometheus:latest
  container_name: prometheus
  ports:
    - "9090:9090"
  volumes:
    - ./prometheus/prometheus.yml:/etc/prometheus/prometheus.yml
  • image — uses the official prom/prometheus:latest image.
  • ports — maps host port 9090 to container port 9090, making the Prometheus web UI available at http://localhost:9090.
  • volumes — mounts your local prometheus/prometheus.yml into the container at the path Prometheus reads on startup. Editing the local file and restarting the container applies the new configuration.

​
Prometheus web UI

Once the stack is running, open http://localhost:9090 in your browser. From the UI you can:
  • Run PromQL queries against collected metrics.
  • Check the status of configured scrape targets under Status → Targets.
  • Inspect loaded configuration under Status → Configuration.

​
Adding scrape targets

To scrape an additional service, append a new entry under scrape_configs. For example, to also scrape a service called my-app that exposes metrics on port 8080: 
global:
  scrape_interval: 15s

scrape_configs:
  - job_name: 'node-exporter'
    static_configs:
      - targets: ['node-exporter:9100']

  - job_name: 'my-app'
    static_configs:
      - targets: ['my-app:8080']
After editing prometheus.yml, restart the Prometheus container for the change to take effect: 
docker compose restart prometheus