在构建阶段将环境变量从 docker-compose 传递到容器 [英] Pass environment variables from docker-compose to container at build stage

问题描述

我正在尝试使用单个 Dockerfile、多个 docker-compose 文件和多个 envoronment_variables 文件为多个环境创建配置.我需要它为每个环境使用具有 python 依赖项的不同文件.

I am trying to create configuration for several environments with a single Dockerfile, several docker-compose files and several envoronment_variables files. I need it to use a different file with python dependencies for each environment.

比方说，我们在两个环境中创建了一个 web 服务:development 和 production.为此，我创建了以下文件结构:

Let's say, we create a web service in two environments: development and production. To achieve this, I create the following file structure:

docker-compose-dev.yml
docker-compose-prod.yml
envs/
  dev.env
  prod.env
web/
  Dockerfile
  requirements_dev.txt 
  requirements_prod.txt

目标是在容器的build 过程中实例化Dockerfile 中requirements_*.txt 文件的正确名称.根据文档，我尝试了这种幼稚的方法，但似乎不起作用:

The objective is to instantiate the proper name of a requirements_*.txt file in the Dockerfile during the container's build process. According to the documentation, I tried this naïve approach, which doesn't seem to work:

1. 将名称定义为环境变量:
   • envs/dev.env: REQUIREMENTS=requirements_dev.txt
   • envs/prod.env: REQUIREMENTS=requirements_prod.txt

在 Dockerfile 中使用这个环境变量:

Use this environment variable in the Dockerfile:

FROM python:3.5
ENV PYTHONUNBUFFERED 1
ENV APP_ROOT /usr/src/app
...
COPY $REQUIREMENTS $APP_ROOT/
RUN pip install -r $APP_ROOT/$REQUIREMENTS

在docker-compose配置中导入对应的定义:

Import the corresponding definition in a docker-compose configuration:

version: '2'

services:
    web:
        build: ./web
        env_file:
            - envs/dev.env   # in docker-compose-dev.yml
            - envs/prod.env   # in docker-compose-prod.yml
        ...

当我运行 docker-compose up --build docker-compose-dev.yml 时，$REQUIREMENTS 变量未在构建过程中定义.

When I run docker-compose up --build docker-compose-dev.yml, the $REQUIREMENTS variable is not defined at the build process.

在 docker-compose 文档中 有一个注释:

注意:如果您的服务指定了构建选项，则在构建过程中环境文件中定义的变量将不会自动可见.使用 build 的 args 子选项来定义构建时环境变量.

但是要使用Dockerfile中的ARG选项，比如ARG REQUIREMENTS，需要一个对应的argsdocker-compose 中的选项，像这样:

But to use the ARG option in the Dockerfile, like ARG REQUIREMENTS, one needs a corresponding args option in docker-compose, like this:

services:
    web:
        build:
            context: ./web
            args:
                - REQUIREMENTS

尽管如此，使用此配置我的测试也失败了，因为根据 文档，Dockerfile中REQUIREMENTS变量的值取自

Nevertheless, with this configuration my tests also failed, because, according to the documentation, the value of the REQUIREMENTS variable in Dockerfile is taken from

Compose 运行的环境

因此，它从我的 shell 中获取值，而不是从 envs/dev.env 中获取值.

Therefore, it takes value from my shell, but not from envs/dev.env.

所以我的问题是:

是否可以将环境变量从docker-compose中的env_file传递到Dockerfile构建时间没有在我的 shell 中本地设置变量?

Is it possible to pass environment variable from env_file in docker-compose to Dockerfile at build time without setting variables locally in my shell?

推荐答案

您的 docker-compose.yml 应如下所示:

Your docker-compose.yml should look like this:

version: '2'
services:
  web:
    build:
      context: ./web
      args:
        REQUIREMENTS: "requirements_dev.txt"

你的 Dockerfile 应该像这样使用 ARG 定义构建参数:

Your Dockerfile should define the build-argument using ARG like this:

FROM python:3.5
ENV PYTHONUNBUFFERED 1
ENV APP_ROOT /usr/src/app
ARG REQUIREMENTS
...
COPY $REQUIREMENTS $APP_ROOT/
RUN pip install -r $APP_ROOT/$REQUIREMENTS

我对此进行了验证并在 Github 创建了一个缩小的功能演示:

I validated this and created a minified functional demo at Github:

https://github.com/jannikweichert/stackoverflow-41747843

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