Prometheus Configuration

Complete guide to Prometheus setup, metric collection, scrape configuration, and recording rules.

Do not use this skill when

•The task is unrelated to prometheus configuration
•You need a different domain or tool outside this scope

Instructions

•Clarify goals, constraints, and required inputs.
•Apply relevant best practices and validate outcomes.
•Provide actionable steps and verification.
•If detailed examples are required, open resources/implementation-playbook.md.

Purpose

Configure Prometheus for comprehensive metric collection, alerting, and monitoring of infrastructure and applications.

Use this skill when

•Set up Prometheus monitoring
•Configure metric scraping
•Create recording rules
•Design alert rules
•Implement service discovery

Prometheus Architecture

code

┌──────────────┐
│ Applications │ ← Instrumented with client libraries
└──────┬───────┘
       │ /metrics endpoint
       ↓
┌──────────────┐
│  Prometheus  │ ← Scrapes metrics periodically
│    Server    │
└──────┬───────┘
       │
       ├─→ AlertManager (alerts)
       ├─→ Grafana (visualization)
       └─→ Long-term storage (Thanos/Cortex)

Installation

Kubernetes with Helm

bash

helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
helm repo update

helm install prometheus prometheus-community/kube-prometheus-stack \
  --namespace monitoring \
  --create-namespace \
  --set prometheus.prometheusSpec.retention=30d \
  --set prometheus.prometheusSpec.storageVolumeSize=50Gi

Docker Compose

yaml

version: '3.8'
services:
  prometheus:
    image: prom/prometheus:latest
    ports:
      - "9090:9090"
    volumes:
      - ./prometheus.yml:/etc/prometheus/prometheus.yml
      - prometheus-data:/prometheus
    command:
      - '--config.file=/etc/prometheus/prometheus.yml'
      - '--storage.tsdb.path=/prometheus'
      - '--storage.tsdb.retention.time=30d'

volumes:
  prometheus-data:

Configuration File

prometheus.yml:

yaml

global:
  scrape_interval: 15s
  evaluation_interval: 15s
  external_labels:
    cluster: 'production'
    region: 'us-west-2'

# Alertmanager configuration
alerting:
  alertmanagers:
    - static_configs:
        - targets:
          - alertmanager:9093

# Load rules files
rule_files:
  - /etc/prometheus/rules/*.yml

# Scrape configurations
scrape_configs:
  # Prometheus itself
  - job_name: 'prometheus'
    static_configs:
      - targets: ['localhost:9090']

  # Node exporters
  - job_name: 'node-exporter'
    static_configs:
      - targets:
        - 'node1:9100'
        - 'node2:9100'
        - 'node3:9100'
    relabel_configs:
      - source_labels: [__address__]
        target_label: instance
        regex: '([^:]+)(:[0-9]+)?'
        replacement: '${1}'

  # Kubernetes pods with annotations
  - job_name: 'kubernetes-pods'
    kubernetes_sd_configs:
      - role: pod
    relabel_configs:
      - source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_scrape]
        action: keep
        regex: true
      - source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_path]
        action: replace
        target_label: __metrics_path__
        regex: (.+)
      - source_labels: [__address__, __meta_kubernetes_pod_annotation_prometheus_io_port]
        action: replace
        regex: ([^:]+)(?::\d+)?;(\d+)
        replacement: $1:$2
        target_label: __address__
      - source_labels: [__meta_kubernetes_namespace]
        action: replace
        target_label: namespace
      - source_labels: [__meta_kubernetes_pod_name]
        action: replace
        target_label: pod

  # Application metrics
  - job_name: 'my-app'
    static_configs:
      - targets:
        - 'app1.example.com:9090'
        - 'app2.example.com:9090'
    metrics_path: '/metrics'
    scheme: 'https'
    tls_config:
      ca_file: /etc/prometheus/ca.crt
      cert_file: /etc/prometheus/client.crt
      key_file: /etc/prometheus/client.key

Reference: See assets/prometheus.yml.template

Scrape Configurations

Static Targets

yaml

scrape_configs:
  - job_name: 'static-targets'
    static_configs:
      - targets: ['host1:9100', 'host2:9100']
        labels:
          env: 'production'
          region: 'us-west-2'

File-based Service Discovery

yaml

scrape_configs:
  - job_name: 'file-sd'
    file_sd_configs:
      - files:
        - /etc/prometheus/targets/*.json
        - /etc/prometheus/targets/*.yml
        refresh_interval: 5m

targets/production.json:

json

[
  {
    "targets": ["app1:9090", "app2:9090"],
    "labels": {
      "env": "production",
      "service": "api"
    }
  }
]

Kubernetes Service Discovery

yaml

scrape_configs:
  - job_name: 'kubernetes-services'
    kubernetes_sd_configs:
      - role: service
    relabel_configs:
      - source_labels: [__meta_kubernetes_service_annotation_prometheus_io_scrape]
        action: keep
        regex: