mysql - Docker为 flask 应用程序撰写数据库url环境变量

Question

尝试使用 docker-compose.yml 而不是像这样单独启动容器:

docker container run --name mysql -d -e MYSQL_RANDOM_ROOT_PASSWORD=yes -e MYSQL_DATABASE=currency -e MYSQL_USER=currency -e MYSQL_PASSWORD=currency mysql/mysql-server:5.7


docker run --name currency -d -p 8000:5000 --rm --link mysql:dbserver -e DATABASE_URL=mysql+pymysql://currency:currency@dbserver/currency currency:latest

单独运行时，flask 应用程序正确找到 DATABASE_URL 并使用 mysql 数据库。

我使用的 docker-compose.yml 文件如下:

version: "2"
services:
    mysql:
        image: mysql/mysql-server:5.7
        environment:
            - MYSQL_RANDOM_ROOT_PASSWORD:yes
            - MYSQL_DATABASE:currency
            - MYSQL_USER:currency
            - MYSQL_PASSWORD:currency
    currency:
        build: .
        links:
            - "mysql:dbserver"
        ports:
            - "8000:5000"
        environment:
            - DATABASE_URL:"mysql+pymysql://currency:currency@dbserver/currency"

当我使用 docker-compose.yml 时，它没有使用 mysql 数据库。我相信由于 docker-compose.yml 中的一些错误，flask 应用程序无法看到环境变量“DATABASE_URL”。 docker-compose.yml 出了什么问题？

Answer 1

首先:确保不使用 links

The --link flag is a legacy feature of Docker. It may eventually be removed. Unless you absolutely need to continue using it, we recommend that you use user-defined networks to facilitate communication between two containers instead of using --link.
One feature that user-defined networks do not support that you can do with --link is sharing environmental variables between containers. However, you can use other mechanisms such as volumes to share environment variables between containers in a more controlled way.

其次，执行 docker exec -it currency bash 在您的货币容器中打开一个 session ，然后执行 echo "DATABASE_URL='${DATABASE_URL}'"在其中，检查环境变量是否已设置。

最后，检查您的情况是否是排序问题(货币在数据库完全启动之前开始)

参见“Control startup order in Compose”。
例如:

version: "2"
services:
  web:
    build: .
    ports:
      - "80:8000"
    depends_on:
      - "db"
    command: ["./wait-for-it.sh", "db:5432", "--", "python", "app.py"]
  db:
    image: postgres