Metric Collection #

Node Exporter mengumpulkan metrik sistem. Tapi sistem produksi terdiri dari lebih dari sekadar CPU dan memory — ada PostgreSQL, nginx, Redis, RabbitMQ, dan puluhan komponen lain yang masing-masing perlu dipantau dengan metrik yang relevan. Ekosistem Prometheus menyediakan exporter untuk hampir semua software populer: agen kecil yang mengekspos metrik dalam format yang bisa di-scrape Prometheus. Mengotomasi instalasi dan konfigurasi exporter ini dengan Ansible memastikan setiap komponen langsung termonitor saat pertama kali diinstal.

PostgreSQL Exporter #

# roles/postgres-exporter/tasks/main.yml
---
- name: Download postgres_exporter
  get_url:
    url: >
      https://github.com/prometheus-community/postgres_exporter/releases/download/
      v{{ postgres_exporter_version }}/postgres_exporter-{{ postgres_exporter_version }}.linux-amd64.tar.gz      
    dest: /tmp/postgres_exporter.tar.gz
    checksum: "sha256:{{ postgres_exporter_checksum }}"

- name: Install postgres_exporter
  unarchive:
    src: /tmp/postgres_exporter.tar.gz
    dest: /usr/local/bin/
    extra_opts: ['--strip-components=1']
    include: ['postgres_exporter']
    remote_src: true
    creates: /usr/local/bin/postgres_exporter

- name: Buat file koneksi database untuk exporter
  template:
    src: postgres_exporter.env.j2
    dest: /etc/postgres_exporter.env
    owner: root
    group: postgres
    mode: '0640'
  notify: Restart postgres_exporter
  no_log: true

- name: Deploy systemd unit file
  template:
    src: postgres_exporter.service.j2
    dest: /etc/systemd/system/postgres_exporter.service
  notify:
    - Reload systemd
    - Restart postgres_exporter

- name: Jalankan postgres_exporter
  systemd:
    name: postgres_exporter
    state: started
    enabled: true

{# templates/postgres_exporter.env.j2 #}
DATA_SOURCE_NAME=postgresql://{{ postgres_exporter_user }}:{{ vault_postgres_exporter_password }}@localhost:5432/postgres?sslmode=disable

{# templates/postgres_exporter.service.j2 #}
[Unit]
Description=Prometheus PostgreSQL Exporter
After=network.target postgresql.service

[Service]
User=postgres
EnvironmentFile=/etc/postgres_exporter.env
ExecStart=/usr/local/bin/postgres_exporter \
  --web.listen-address=:9187 \
  --log.level=warn
Restart=always
RestartSec=5

[Install]
WantedBy=multi-user.target

Nginx Exporter #

# roles/nginx-exporter/tasks/main.yml
---
# nginx stub_status harus diaktifkan dulu di konfigurasi nginx
- name: Aktifkan stub_status di nginx
  blockinfile:
    path: /etc/nginx/conf.d/stub_status.conf
    create: true
    block: |
      server {
          listen 127.0.0.1:8080;
          server_name localhost;
          location /nginx_status {
              stub_status;
              allow 127.0.0.1;
              deny all;
          }
      }      
    marker: "# {mark} ANSIBLE MANAGED — nginx stub_status"
  notify: Reload nginx

- name: Install nginx-prometheus-exporter
  get_url:
    url: >
      https://github.com/nginxinc/nginx-prometheus-exporter/releases/download/
      v{{ nginx_exporter_version }}/nginx-prometheus-exporter_{{ nginx_exporter_version }}_linux_amd64.tar.gz      
    dest: /tmp/nginx_exporter.tar.gz

- name: Extract dan install binary
  unarchive:
    src: /tmp/nginx_exporter.tar.gz
    dest: /usr/local/bin/
    include: ['nginx-prometheus-exporter']
    remote_src: true
    creates: /usr/local/bin/nginx-prometheus-exporter

- name: Deploy systemd unit file
  template:
    src: nginx-exporter.service.j2
    dest: /etc/systemd/system/nginx-exporter.service
  notify:
    - Reload systemd
    - Restart nginx-exporter

Redis Exporter #

# roles/redis-exporter/tasks/main.yml
---
- name: Install redis_exporter
  get_url:
    url: >
      https://github.com/oliver006/redis_exporter/releases/download/
      v{{ redis_exporter_version }}/redis_exporter-v{{ redis_exporter_version }}.linux-amd64.tar.gz      
    dest: /tmp/redis_exporter.tar.gz

- name: Extract dan install
  unarchive:
    src: /tmp/redis_exporter.tar.gz
    dest: /usr/local/bin/
    extra_opts: ['--strip-components=1']
    include: ['redis_exporter']
    remote_src: true

- name: Deploy konfigurasi dan systemd unit
  template:
    src: redis-exporter.service.j2
    dest: /etc/systemd/system/redis_exporter.service
  notify:
    - Reload systemd
    - Restart redis_exporter

{# templates/redis-exporter.service.j2 #}
[Unit]
Description=Prometheus Redis Exporter
After=network.target redis.service

[Service]
ExecStart=/usr/local/bin/redis_exporter \
  --redis.addr=redis://127.0.0.1:{{ redis_port | default(6379) }} \
  {% if redis_password is defined %}
  --redis.password={{ redis_password }} \
  {% endif %}
  --web.listen-address=:9121
Restart=always

[Install]
WantedBy=multi-user.target

Konfigurasi Scrape Dinamis via File SD #

Untuk infrastruktur yang berubah-ubah, static_configs di prometheus.yml tidak cukup fleksibel. File-based service discovery memungkinkan target scrape diupdate tanpa reload Prometheus:

# playbooks/update-scrape-targets.yml
---
- name: Update daftar scrape target Prometheus
  hosts: prometheus_servers
  tasks:
    - name: Generate file target untuk setiap exporter
      template:
        src: "{{ item.template }}"
        dest: "/etc/prometheus/file_sd/{{ item.filename }}"
        owner: prometheus
        mode: '0644'
      loop:
        - template: targets-node.json.j2
          filename: targets-node.json
        - template: targets-postgres.json.j2
          filename: targets-postgres.json
        - template: targets-nginx.json.j2
          filename: targets-nginx.json
      # Tidak perlu reload Prometheus — file_sd otomatis memuat ulang

{# templates/targets-node.json.j2 #}
[
{% for host in groups['all'] %}
  {
    "targets": ["{{ hostvars[host]['ansible_default_ipv4']['address'] }}:9100"],
    "labels": {
      "hostname": "{{ host }}",
      "environment": "{{ hostvars[host]['env'] | default(env) }}",
      "role": "{{ group_names | first }}"
    }
  }{{ '' if loop.last else ',' }}
{% endfor %}
]

Konfigurasi Prometheus untuk menggunakan file_sd:

# Di prometheus.yml — gunakan file_sd_configs bukan static_configs
scrape_configs:
  - job_name: node_exporter
    file_sd_configs:
      - files:
          - /etc/prometheus/file_sd/targets-node.json
        refresh_interval: 5m    # Cek file setiap 5 menit

  - job_name: postgres_exporter
    file_sd_configs:
      - files:
          - /etc/prometheus/file_sd/targets-postgres.json

Metrik Aplikasi Custom #

Untuk aplikasi yang tidak punya exporter bawaan, tambahkan endpoint /metrics menggunakan library Prometheus client:

# roles/app-metrics/tasks/main.yml
---
- name: Install prometheus client library
  pip:
    name: prometheus-client
    virtualenv: "{{ app_venv }}"

- name: Verifikasi endpoint metrics tersedia
  uri:
    url: "http://localhost:{{ app_port }}/metrics"
    status_code: 200
  register: metrics_check
  changed_when: false

# Tambahkan ke scrape config
- name: Tambahkan aplikasi ke file SD target
  template:
    src: targets-app.json.j2
    dest: /etc/prometheus/file_sd/targets-{{ app_name }}.json
    owner: prometheus
    mode: '0644'
  delegate_to: "{{ groups['prometheus_servers'][0] }}"

Ringkasan #

Setiap komponen stack perlu exporter-nya sendiri: Node Exporter (OS), postgres_exporter (PostgreSQL), nginx-prometheus-exporter (nginx), redis_exporter (Redis).
Instal exporter sebagai bagian dari role komponen — saat nginx diinstal, nginx-exporter ikut terinstal otomatis.
File-based service discovery lebih fleksibel dari static_configs — target bisa diupdate tanpa reload Prometheus, dan Ansible bisa menggenerate file target dari inventory.
Simpan credential exporter (database password) di Ansible Vault dan kirim ke exporter via environment variable atau file yang permission-nya dibatasi.
Gunakan checksum saat mendownload binary exporter — memverifikasi integritas file sebelum diinstal adalah praktik keamanan dasar.
Untuk aplikasi custom, implementasikan endpoint /metrics menggunakan Prometheus client library — lebih baik dari solusi monitoring custom yang tidak standar.

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