Docker Compose

Compose runs a set of related containers as one project. Use the current Compose plugin through docker compose. The old standalone Compose v1 command is retired and should not be used for new work.

Check the plugin.

docker compose version
docker compose ls

Compose files

The preferred file name is compose.yaml. Current Compose files follow the Compose Specification; do not add a top-level version key to new files.

The sample below defines three services: a MySQL database, a Flask API, and an nginx-hosted frontend.

name: student-stack
services:
  db:
    image: db-app:local
    container_name: db
    ports:
      - "3306:3306"
    volumes:
      - type: bind
        source: ./mysql/docker-entrypoint-initdb.d
        target: /docker-entrypoint-initdb.d
        consistency: consistent
    environment:
      MYSQL_ROOT_PASSWORD: "oneoffcoder"
    healthcheck:
      test: mysqladmin ping -h localhost -p$$MYSQL_ROOT_PASSWORD && test '0' -eq $$(ps aux | awk '{print $$11}' | grep -c -e '^mysql$$')
  flask:
    image: rest-app:local
    container_name: rest
    ports:
      - "5000:5000"
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:5000"]
      interval: 60s
      timeout: 10s
      retries: 3
      start_period: 40s
    depends_on:
      - db
  ng:
    image: ui-app:local
    container_name: ui
    ports:
      - "80:80"
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:80"]
      interval: 60s
      timeout: 10s
      retries: 3
      start_period: 40s
    depends_on:
      - flask
      - db

The YAML file is mostly self-explanatory.

We create three services: db, flask and ng.
Each service has a specified container image: db-app:local, rest-app:local and ui-app:local.
The database mounts initialization scripts and receives its root password through environment configuration.
Health checks describe how Compose can tell whether a service is healthy.

For services that need a dependency to be healthy before startup, use long-form depends_on.

services:
  api:
    image: rest-app:local
    depends_on:
      db:
        condition: service_healthy

Environment files

Keep local defaults in a .env file or pass an explicit environment file. Do not commit real secrets.

docker compose --env-file .env.local config
docker compose --env-file .env.local up --build

Profiles

Profiles let optional services stay out of the default development loop.

services:
  worker:
    image: worker-app:local
    profiles:
      - jobs

Run the optional service only when the profile is requested.

docker compose --profile jobs up

Secrets and configs

Compose supports secrets and configs. For local development, a secret can be mounted from a file.

services:
  api:
    image: rest-app:local
    secrets:
      - db_password

secrets:
  db_password:
    file: ./secrets/db_password.txt

The application reads the mounted file rather than receiving the value through an environment variable.

Networks and volumes

Compose creates a project network by default. Add named networks when you need explicit boundaries, and use named volumes for persistent state.

services:
  db:
    image: db-app:local
    volumes:
      - db_data:/var/lib/mysql
    networks:
      - backend

volumes:
  db_data:

networks:
  backend:

Daily commands

The commands below cover the normal loop.

docker compose -f compose.yaml config
docker compose -f compose.yaml up --build
docker compose -f compose.yaml ps
docker compose -f compose.yaml logs -f
docker compose -f compose.yaml exec flask sh
docker compose -f compose.yaml down --volumes

Use Compose for local development, integration tests, and simple single-host deployments. For managed cloud deployments, translate the same image and configuration ideas into the target platform’s native model, such as ECS task definitions or Kubernetes manifests.

Dockerfiles

MySQL

FROM mysql:latest

Flask

FROM python:3

WORKDIR /rest-app
COPY ./rest-app .
RUN pip install --no-cache-dir requests flask flask-cors mysql-connector-python SQLAlchemy

CMD [ "python", "./app.py" ]

Angular

FROM node:lts AS node_builder
WORKDIR /tmp/ui-app
COPY ./ui-app .
RUN npm install -g @angular/cli@latest
RUN npm install
RUN ng build

FROM nginx:alpine 
COPY --from=node_builder /tmp/ui-app/dist/ui-app /usr/share/nginx/html
EXPOSE 80