Docker Compose: Change env variables

Question

I have writte a docker-compose.yml file to create a multi-container app with nodejs and mongodb (so 2 containers), and I want to make some options configurable, as the choice of server address and port. To do that, I have written what follows in docker-compose.yml to set them as env variables:

..
    web:
      environment:
        - PORT=3000
        - ADDRESS=xxx.xxx.xxx.xxx
..

Within the source code of my application, I use process.env.PORT and process.env.ADDRESS to refer to these variables.

But how can I do if I want to change those values, and for example set PORT=3001? I have to use docker-compose build and docker-compose up again and build all the application, included mongodb container?

Environment variables are runtime instructions, just change them in the docker-compose.yml then re-run docker-compose up. — johnharris85
– johnharris85, Commented May 8, 2017 at 14:44
As johnharris85 mentioned, re-running docker-compose up would be enough. Alternatively to using the environment variables in docker-compose.yml, you could use an environment file: docs.docker.com/compose/env-file — Miguel Marques
– Miguel Marques, Commented May 9, 2017 at 16:37

Andy Shinn · Accepted Answer · 2017-05-09 18:53:45Z

27

I have to use docker-compose build and docker-compose up again and build all the application, included mongodb container?

Not build, just up. They are runtime options, not build options. Changing them in the docker-compose.yml file and then doing a docker-compose up again should recreate the containers with the new environment variables.

Alternatively, you can specify environment variables outside the docker-compose.yml file to make for easier changes:

One of these methods is to use a .env file in the same folder that you execute docker-compose form (see https://docs.docker.com/compose/env-file/ for information on it).
Another option is to interpolate environment variables from your shell. You could specify them such as - PORT=${APP_PORT} and then export APP_PORT=3000 on your shell before running docker-compose. See https://docs.docker.com/compose/environment-variables/ for more information.

answered May 9, 2017 at 18:53

Andy Shinn

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2 Comments

Realizt30 Over a year ago

why docker-compose restart won't reload the .env variables changes?

Andy Shinn Over a year ago

Because environment is set at container creation. You will need to recreate the containers using something like docker-compose up --force-recreate.

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