如何将 docker 环境变量传递给 npm 脚本？

Question

As the title says...As a noobie I've given this a good attempt but can't seem to figure it out.

I have a dockerfile

FROM node:12
WORKDIR /app
COPY . /app
RUN npm config set registry https://registry.npmjs.org/
RUN npm install
EXPOSE 8080
ENTRYPOINT ["npm", "start",]
CMD [ "--", "-e=$ENVIRONMENT", "-t=$TESTS" ]

and a script in my package.json like so:

"scripts": {
    "start": "node main.js"
  }

Main.js is expecting two arguments. e & t. I am struggling to pass these in to the container to then give to the script to run main.js (note there is a reason why im running it through a script ive just made this example simple)

To run my npm script I can do this:

npm start -- -e=abc -t=xyz

So I have tried this but no joy:

docker run -e ENVIRONMENT=abc -e TESTS=xyz myimage  

Thanks

Answer 1

When you use the JSON form of CMD (or ENTRYPOINT or RUN ), there is no interpolation at all; your script should literally see the string -e=$ENVIRONMENT as the argument. Instead you need to use the shell form, which will wrap this in a shell that expands environment variables. You can't do this with this particular split of ENTRYPOINT and CMD , but at the same time, it's not really necessary; just put the whole thing in CMD .

# No ENTRYPOINT
# No quoting; Docker wraps this in `sh -c ...`
CMD npm start -- -e="$ENVIRONMENT" -t="$TESTS"

You can also handle these directly in your application. The yargs library for example has a .env() function that allows environment variables to be used directly as options. You could also make process.env.TESTS be the default value for the option if it's not provided directly. This approach gets around the trouble of constructing (and possibly extending) a valid command line with the combination of arguments you need.