How to Deploy Loki with Docker Compose for Scalable Log Aggregation

Loki's first stable version was released on November 19, 2019 by Grafana Labs. It is a horizontally scalable, highly available, multi‑tenant log aggregation system that emphasizes ease of installation and resource efficiency.

Features

Advantages

Loki uses the same label‑based indexing as Prometheus, allowing log queries and metric queries to share labels, reducing storage cost and query switching overhead.

Lower cost compared with ELK, offering better cost‑effectiveness.

Seamless integration with Grafana for log visualization, filtering, and navigation.

Disadvantages

The technology is relatively new, so community forums are less active.

Functionality is focused on log viewing; it lacks the powerful data processing and cleaning capabilities of ELK, and cannot be combined with other big‑data tools for advanced log processing.

Components

1. Loki – the main server that stores logs and handles queries.
2. Promtail – the agent that collects logs and sends them to Loki.
3. Grafana – UI for visualization.

The installation uses Docker.

Installation Steps

1.0 Install docker‑compose

curl -L "https://github.com/docker/compose/releases/download/1.28.3/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
chmod +x /usr/local/bin/docker-compose

2.0 Download docker‑compose.yaml

wget https://raw.githubusercontent.com/grafana/loki/v2.2.0/production/docker-compose.yaml -O docker-compose.yaml

version: "3"

networks:
  loki:

services:
  loki:
    image: grafana/loki:2.0.0
    ports:
      - "3100:3100"
    command: -config.file=/etc/loki/local-config.yaml
    networks:
      - loki

  promtail:
    image: grafana/promtail:2.0.0
    volumes:
      - /var/log:/var/log
    command: -config.file=/etc/promtail/config.yml
    networks:
      - loki

  grafana:
    image: grafana/grafana:latest
    ports:
      - "3000:3000"
    networks:
      - loki

3.0 Start services docker-compose -f docker-compose.yaml up 4.0 Verify services

Open http://192.168.106.202:3000/ (default Grafana credentials: admin/admin).

5.0 Configure data source in Grafana

Set the Loki endpoint and test the connection.

6.0 Promtail configuration details

Promtail runs as a container that reads logs from /var/log and pushes them to Loki.

server:
  http_listen_port: 9080
  grpc_listen_port: 0

positions:
  filename: /tmp/positions.yaml

clients:
  - url: http://loki:3100/loki/api/v1/push

scrape_configs:
  - job_name: system
    static_configs:
      - targets:
          - localhost
        labels:
          job: varlogs
          __path__: /var/log/*log

7.0 Add a second server for log collection

Create a config.yml for the new Promtail instance and a corresponding docker-compose.yaml:

mkdir /root/promtail && cd /root/promtail
cat config.yml
server:
  http_listen_port: 9080
  grpc_listen_port: 0

positions:
  filename: /tmp/positions.yaml

clients:
  - url: http://192.168.106.202:3100/loki/api/v1/push

scrape_configs:
  - job_name: mysql
    static_configs:
      - targets:
          - localhost
        labels:
          job: mysql
          __path__: /var/log/*log

version: "v1"
services:
  promtail:
    image: grafana/promtail:2.0.0
    container_name: promtail-node
    volumes:
      - /root/promtail/config.yml:/etc/promtail/config.yml
      - /var/log:/var/log
    network_mode: 'host'

Start with docker-compose up -d.

8.0 Query logs in Loki

Use Grafana's Explore view to run log queries and retrieve matching log entries.