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お題は不問！Qiita Engineer Festa 2024で記事投稿！
Qiita Engineer Festa20242024年7月17日まで開催中！
@Yasushi-Mo(Yasushi Mo)

【Docker Compose】compose.yaml で環境変数を利用する

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はじめに

この記事では、compose.yaml で環境変数を利用する方法について記載します。

開発環境

開発環境は以下の通りです。

  • Windows 11
  • Docker Engine 26.1.1
  • Docker Compose 2
  • PHP 8.3
  • MySQL 8.4.0
  • Mailpit 1.18

環境変数に置き換える

以下の compose.yaml のポート番号とデータベース接続情報を .env ファイルを作成して、そちらに定義します。

compose.yaml
services:
  app:
    ports:
      - "8000:8000"
    volumes:
      - type: bind
        source: ./src
        target: /my-work
    build: ./docker/app
  db:
    environment:
      - MYSQL_ROOT_PASSWORD=password
      - MYSQL_USER=app
      - MYSQL_PASSWORD=password
      - MYSQL_DATABASE=sample
      - TZ=Asia/Tokyo
    ports:
      - "3306:3306"
    volumes:
      - type: volume
        source: db-compose-volume
        target: /var/lib/mysql
      - type: bind
        source: ./docker/db/init
        target: /docker-entrypoint-initdb.d
    image: mysql:8.4.0
  mail:
    environment:
      - TZ=Asia/Tokyo
      - MP_DATABASE=/data/mailpit.db
    ports:
      - "8025:8025"
    volumes:
      - type: volume
        source: mail-compose-volume
        target: /data
    image: axllent/mailpit:v1.18
volumes:
  db-compose-volume:
  mail-compose-volume:

.env ファイルを作成し、app / db / mail サービスのホストマシンのポート番号とデータベース接続情報を定義します、

.env
APP_HOST_MACHINE_PORT=8000

DB_ROOT_PASSWORD=password
DB_USER=app
DB_PASSWORD=password
DB_DATABASE=sample
DB_HOST_MACHINE_PORT=3306

MAIL_HOST_MACHINE_PORT=8025

定義した環境変数を compose.yaml で ${VAR_NAME} という形式で利用します。

compose.yaml
services:
  app:
    ports:
      - "${APP_HOST_MACHINE_PORT}:8000"
    volumes:
      - type: bind
        source: ./src
        target: /my-work
    build: ./docker/app
  db:
    environment:
      - MYSQL_ROOT_PASSWORD=${DB_ROOT_PASSWORD}
      - MYSQL_USER=${DB_USER}
      - MYSQL_PASSWORD=${DB_PASSWORD}
      - MYSQL_DATABASE=${DB_DATABASE}
      - TZ=Asia/Tokyo
    ports:
      - "${DB_HOST_MACHINE_PORT}:3306"
    volumes:
      - type: volume
        source: db-compose-volume
        target: /var/lib/mysql
      - type: bind
        source: ./docker/db/init
        target: /docker-entrypoint-initdb.d
    image: mysql:8.4.0
  mail:
    environment:
      - TZ=Asia/Tokyo
      - MP_DATABASE=/data/mailpit.db
    ports:
      - "${MAIL_HOST_MACHINE_PORT}:8025"
    volumes:
      - type: volume
        source: mail-compose-volume
        target: /data
    image: axllent/mailpit:v1.18
volumes:
  db-compose-volume:
  mail-compose-volume:

docker compose config で指定した環境変数が設定されていることを確認できます。

name: docker-mail-app
services:
  app:
    build:
      context: C:\Users\ymori\Documents\GitHub\docker-mail-app\docker\app
      dockerfile: Dockerfile
    networks:
      default: null
    ports:
      - mode: ingress
        target: 8000
        published: "8000"
        protocol: tcp
    volumes:
      - type: bind
        source: C:\Users\ymori\Documents\GitHub\docker-mail-app\src
        target: /my-work
  db:
    environment:
      MYSQL_DATABASE: sample
      MYSQL_PASSWORD: password
      MYSQL_ROOT_PASSWORD: password
      MYSQL_USER: app
      TZ: Asia/Tokyo
    image: mysql:8.4.0
    networks:
      default: null
    ports:
      - mode: ingress
        target: 3306
        published: "3306"
        protocol: tcp
    volumes:
      - type: volume
        source: db-compose-volume
        target: /var/lib/mysql
      - type: bind
        source: C:\Users\ymori\Documents\GitHub\docker-mail-app\docker\db\init
        target: /docker-entrypoint-initdb.d
  mail:
    environment:
      MP_DATABASE: /data/mailpit.db
      TZ: Asia/Tokyo
    image: axllent/mailpit:v1.18
    networks:
      default: null
    ports:
      - mode: ingress
        target: 8025
        published: "8025"
        protocol: tcp
    volumes:
      - type: volume
        source: mail-compose-volume
        target: /data
networks:
  default:
    name: docker-mail-app_default
volumes:
  db-compose-volume:
    name: docker-mail-app_db-compose-volume
  mail-compose-volume:
    name: docker-mail-app_mail-compose-volume

環境変数のデフォルト値と必須設定

ポートはデフォルト値を設定し、データーベース接続情報は必須設定にします。

  • ${VAR_NAME:-default} : VAR_NAME が未定義 or 空の場合、default とする
  • ${VAR_NAME:?error} : VAR_NAME が未定義 or 空の場合、error を含むメッセージを表示して終了
compose.yaml
services:
  app:
    ports:
      - "${APP_HOST_MACHINE_PORT:-8000}:8000"
    volumes:
      - type: bind
        source: ./src
        target: /my-work
    build: ./docker/app
  db:
    environment:
      - MYSQL_ROOT_PASSWORD=${DB_ROOT_PASSWORD:?review .env}
      - MYSQL_USER=${DB_USER:?review .env}
      - MYSQL_PASSWORD=${DB_PASSWORD:?review .env}
      - MYSQL_DATABASE=${DB_DATABASE:?review .env}
      - TZ=Asia/Tokyo
    ports:
      - "${DB_HOST_MACHINE_PORT:-3306}:3306"
    volumes:
      - type: volume
        source: db-compose-volume
        target: /var/lib/mysql
      - type: bind
        source: ./docker/db/init
        target: /docker-entrypoint-initdb.d
    image: mysql:8.4.0
  mail:
    environment:
      - TZ=Asia/Tokyo
      - MP_DATABASE=/data/mailpit.db
    ports:
      - "${MAIL_HOST_MACHINE_PORT:-8025}:8025"
    volumes:
      - type: volume
        source: mail-compose-volume
        target: /data
    image: axllent/mailpit:v1.18
volumes:
  db-compose-volume:
  mail-compose-volume:

試しに .env のポートの環境変数を全て削除して、docker compose config を実行します。

docker compose config

デフォルト値として設定された値が表示されます。

name: docker-mail-app
services:
  app:
    build:
      context: C:\Users\ymori\Documents\GitHub\docker-mail-app\docker\app
      dockerfile: Dockerfile
    networks:
      default: null
    ports:
      - mode: ingress
        target: 8000
        published: "8000"
        protocol: tcp
    volumes:
      - type: bind
        source: C:\Users\ymori\Documents\GitHub\docker-mail-app\src
        target: /my-work
  db:
    environment:
      MYSQL_DATABASE: sample
      MYSQL_PASSWORD: password
      MYSQL_ROOT_PASSWORD: password
      MYSQL_USER: app
      TZ: Asia/Tokyo
    image: mysql:8.4.0
    networks:
      default: null
    ports:
      - mode: ingress
        target: 3306
        published: "3306"
        protocol: tcp
    volumes:
      - type: volume
        source: db-compose-volume
        target: /var/lib/mysql
      - type: bind
        source: C:\Users\ymori\Documents\GitHub\docker-mail-app\docker\db\init
        target: /docker-entrypoint-initdb.d
  mail:
    environment:
      MP_DATABASE: /data/mailpit.db
      TZ: Asia/Tokyo
    image: axllent/mailpit:v1.18
    networks:
      default: null
    ports:
      - mode: ingress
        target: 8025
        published: "8025"
        protocol: tcp
    volumes:
      - type: volume
        source: mail-compose-volume
        target: /data
networks:
  default:
    name: docker-mail-app_default
volumes:
  db-compose-volume:
    name: docker-mail-app_db-compose-volume
  mail-compose-volume:
    name: docker-mail-app_mail-compose-volume

今度は DB_ROOT_PASSWORD=password を削除して確認してみます。

docker compose config

error を含むメッセージが表示されます。

error while interpolating services.db.environment.[]: required variable DB_ROOT_PASSWORD is missing a value: review .env

参考

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