docker-compose Getting started with docker-compose Create a simple application

Example

This example comes from the official document. Suppose you have a python application using redis as backend. After writing Dockerfile, create a docker-compose.yml file like this:

version: '2'
services:
  web:
    build: .
    ports:
     - "5000:5000"
    volumes:
     - .:/code
    depends_on:
     - redis
  redis:
    image: redis

Then run docker-compose up will setup the entire application includes: python app and redis.

---

• version: '2' is the version of the docker-compose file syntax
• services: is a section that describes the services to run
• web: and redis: are the names of the services to start, their contents describe how docker should start containers for those services
• depends_on implies a dependency of web to redis and therefor docker-compose first starts the redis container and then the web container. Nevertheless does docker-compose not wait until the redis container is ready before starting the web container. To achieve this you have to use a script that delays the start of the application server or whatever until the redis container can perform requests.

A volumes and networks section can be added as well. Using the volumes section allows for disconnected volume that can live independently of the docker compose services section. The networks section has a similar result.

The redis section of services would have to adjusted like so:

redis:
  image: redis
  volumes:
    - redis-data:/code
  networks:
    -back-tier 

Next, add the following sections to the bottom of the docker compose version 2 file.

volumes:
  # Named volume
  redis-data: 
    driver: local
networks:
  back-tier:
    driver: bridge

redis-data provides an accessible label from the services section. driver:local sets the volume to the local file system.

back-tier sets the networks section label to be accessible in the services section as bridged.