Prometheus Service Discovery Explained

There are two main ways in which the Prometheus system implements automatic service discovery: static configuration and dynamic discovery.

1. Static configuration: Manually defining the target services to monitor in the Prometheus configuration file. This method requires listing the IP addresses, ports, and other information of all services to be monitored in the configuration file, after which Prometheus will periodically poll these target services to collect metric data.

Static targets are defined in the sample configuration file.

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

1. Dynamic discovery: Prometheus also supports dynamically discovering target services through service discovery tools. This enables the dynamic discovery and monitoring of new service instances based on their labels, health status, and more.

Using Consul for dynamic discovery in the sample configuration file.

- job_name: 'consul'
  consul_sd_configs:
    - server: 'localhost:8500'
      services: []
      tags: ['prometheus']

Prometheus will fetch all services with the “prometheus” label from Consul, and start monitoring the metrics of these services.

In general, Prometheus’s auto-discovery feature effectively streamlines the configuration and maintenance of monitoring systems, enhancing the flexibility and scalability of the system.