Prometheus Configuration Guide

Prometheus utilizes two configuration methods: command-line flags and configuration files. Command-line flags set immutable system parameters like storage locations and data retention policies, while configuration files manage scraping jobs, instances, and rule file loading.

To access all available command-line options, execute:

./prometheus -h

Runtime Configuration Reloading

Prometheus supports configuration reloading without downtime. Invalid configurations prevent changes from being applied. Reloads are triggered by:

1. Sending a SIGHUP signal to the process
2. Posting to the /-/reload endpoint when the --web.enable-lifecycle flag is enabled

Rule files are also reloaded during this process.

Configuration File Format

Specify the configuration file using the --config.file flag. Files use YAML format with optional parameters indicated by brackets. Default values apply to non-list parameters.

The documentation defines generic placeholders for various data types:

• Boolean values (true/false)
• Duration strings matching regex patterns
• Identifiers, strings, and URLs
• Hostnames with optional ports
• HTTP/HTTPS protocol specifications
• Template-expandable strings

Example: Basic Scrape Configuration

global:
  scrape_interval: 15s
  evaluation_interval: 15s

scrape_configs:
  - job_name: 'prometheus'
    static_configs:
      - targets: ['localhost:9090']

  - job_name: 'kubernetes-pods'
    kubernetes_sd_configs:
      - role: pod

A valid example configuration is available in the official Prometheus documentation.