Docker Compose

Updated Mar 11, 2022 ·

Overview

Docker Compose is a tool that helps define and manage multi-container applications with the Docker engine. It simplifies configuration and deployment using a single file.

Configuration is stored in compose.yml or compose.yaml.
Older formats use docker-compose.yml or docker-compose.yaml.
Makes it easy to share or demo applications.

Here’s a comparison between running multiple containers using individual RUN commands and using Docker Compose.

First Method - Multiple RUNs

docker run voting-app
docker run redis
docker run worker
docker run db
docker run result-app

Second Method - Using Docker Compose

# docker-compose.yml
services:
    web:
        image: "voting-app"
    cache:
        image: "db"
    messaging:
        image: "worker"
    db:
        image: "db"
    result:
        image: "result-app"

The second method is cleaner and more organized. To run the entire stack defined in docker-compose.yml, execute:

docker-compose up

NOTE

Note: This command is applicable only for multiple containers on a single Docker host.

Adding More Details

You can enhance the docker-compose.yml file with additional configurations:

services:
  redis:
      image: "redis"
  db:
      image: postgres:9.4
  vote:
      build: ./vote
      ports:
          - 5000:80
      links:
          - redis
  result:
      build: ./result
      ports:
          - 5001:80
      links:
          - db
  worker:
      image: worker
      links:
          - db
          - redis

Docker Compose Versions

There are three versions of a Docker Compose file. For versions 2 and 3, you must specify the version.

Version 1

All containers are attached to the default bridge network and use links for communication.

redis:
    image: redis
db:
    image: postgres:9.4
vote:
    image: voting-app
    ports:
        - 5000:80
    links:
        - redis

Version 2

A dedicated network is automatically created for the application, and containers can have dependencies.

version: '2'
services:
    redis:
        image: redis
    db:
        image: postgres:9.4
    vote:
        image: voting-app
        ports:
            - 5000:80
        depends_on:
            - redis

Version 3

Similar to version 2 but includes support for Docker Swarm.

version: '3'
services:
    redis:
        image: redis
    db:
        image: postgres:9.4
    vote:
        image: voting-app
        ports:
            - 5000:80

Docker Compose Commands

The docker-compose commands outlined here are essential for managing your containerized applications. The --build option rebuilds the images specified in the docker-compose file before starting the containers.

To start an application, navigate to the directory containing the docker-compose.yaml file.

Run the following command:
```
docker compose up
```
For older systems, use:
```
docker-compose up
```
Use the -f option to specify a file with a different name or location:
```
docker compose -f custom-file.yaml up
```
Add -d to detach and run containers in the background:
```
docker compose up -d
```
info
Running docker compose up creates containers and their network automatically.

To view the running containers:

docker-compose ps

If executed in a directory without a docker-compose file, you'll see an error:

ERROR:
        Can't find a suitable configuration file in this directory or any
        parent. Are you in the right directory?

        Supported filenames: docker-compose.yml, docker-compose.yaml, compose.yml, compose.yaml 

To shut down all running resources, including containers and networks:
```
docker compose down
```
Use the -f option if it was used during startup:
```
docker compose -f custom-file.yaml down
```

Overview​

Adding More Details​

Docker Compose Versions​

Docker Compose Commands​

Overview

Adding More Details

Docker Compose Versions

Docker Compose Commands