Setting Up a Grafana Dashboard for Docker Logs with Loki and Promtail

Grafana Loki is a horizontally-scalable, highly-available, multi-tenant log aggregation system inspired by Prometheus, making it a great tool for analyzing Docker logs. In this guide, we’ll walk through setting up a Grafana dashboard for a Docker environment with Loki and Promtail.

Step 1: Docker Compose file

First, we need to create a docker-compose.yml file to define our Grafana, Loki, and Promtail services. Save the following as docker-compose.yml:

version: "3"
services:
  grafana:
    image: grafana/grafana:latest
    ports:
      - "3000:3000"
    networks:
      - loki

  loki:
    image: grafana/loki:latest
    volumes:
      - ./loki-data:/loki
    networks:
      - loki
  promtail:
    image: grafana/promtail:latest
    volumes:
      - "/var/log:/var/log"
      - "/var/lib/docker/containers:/var/lib/docker/containers"
      - "/var/run/docker.sock:/var/run/docker.sock"
      - "./promtail-config.yaml:/etc/promtail/config.yaml"
    command: "-config.file=/etc/promtail/config.yaml"
    networks:
      - loki
networks:
  loki:

Step 2: Promtail Configuration

Next, we create the Promtail configuration. This file instructs Promtail which logs to scrape. Save the following as promtail-config.yaml:

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: docker
    pipeline_stages:
      - docker: {}
    static_configs:
      - targets:
          - localhost
        labels:
          job: docker
          __path__: /var/lib/docker/containers/*/*-json.log

This configuration tells Promtail to scrape Docker logs from the /var/lib/docker/containers/*/*-json.log path and send them to Loki.

Step 3: Run Docker Compose

With the docker-compose.yml and promtail-config.yaml files ready, we can run our Docker environment with the command:

docker-compose up

This command will start Grafana, Loki, and Promtail.

Step 4: Configure Grafana

Once you have all three components running, navigate to http://localhost:3000 in your web browser and you should see the Grafana login page. Use the default credentials admin for both username and password, and you'll be prompted to change the password.

Next, we need to add Loki as a data source:

1. Click the Gear Icon on the left panel and select “Data Sources”.
2. Click “Add data source”.
3. Select “Loki” from the list.
4. For the URL, enter http://loki:3100.
5. Click “Save & Test”.

Loki is now set up as a data source!

Step 5: Visualize Docker Logs

Finally, it’s time to create a dashboard to display our Docker logs:

1. Click the Plus Icon on the left panel and select “Dashboard”.
2. Click “Add new panel”.
3. From the Query dropdown, select “Loki”.
4. In the Query field, enter your LogQL query, {job="docker"}.
5. Click “Apply” to save the panel.
6. Click the Disk Icon at the top-right to save the dashboard.

You should now see a Grafana dashboard displaying your Docker logs!