docker-compose 内插环境变量：使用 docker-compose 提供的默认变量

Question

I need some help with the following template:

services:

nginx:
  image: nginx
  restart: unless-stopped
  labels:
    - "traefik.enable=true"
    - "traefik.http.routers.nginx-${COMPOSE_PROJECT_NAME}.rule=Host(`fuu.bar`)"
  networks:
    - treafik

My goal is to create a template which I can use eg in portainer with almost zero configuration.

I thought that the following variables are available in docker-compose config but the expression ${COMPOSE_PROJECT_NAME} results in an empty string: docker-compose config

services:

nginx:
  image: nginx
  restart: unless-stopped
  labels:
    - "traefik.enable=true"
    - "traefik.http.routers.nginx-.rule=Host(`fuu.bar`)"
  networks:
    - treafik

Are there any default environment variables provided by docker-compose which I can use for environment interpolation?

---- Update

I use traefik (v2) as a reverse proxy. To make the containers available through treafik, you need to define routers on every service. The router name has to be unique. Lets imagine you deploy 2 or more stacks of the above template. The router name has to be unique for all services across all stacks. Because Im a lazy guy, I tried to simply integrate the environment variable COMPOSE_PROJECT_NAME (which I know is already unique in my setup because every stack must have a unique name). But the variable is not available when deploying the stack. Of course, I could simply define the variable COMPOSE_PROJECT_NAME by myself in a .env-file, but i hoped that there are any default environment variables provided by docker.

Answer 1

You can use environment variables to passing strings to your docker file. There are many ways through docker documentation . For example:

You can set default values for any environment variables referenced in the Compose file, or used to configure Compose, in an environment file named .env. The .env file path is as follows:

• Starting with +v1.28, .env file is placed at the base of the project directory
• Project directory can be explicitly defined with the --file option or COMPOSE_FILE environment variable. Otherwise, it is the current working directory where the docker compose command is executed (+1.28).
• For previous versions, it might have trouble resolving .env file with --file or COMPOSE_FILE. To work around it, it is recommended to use --project-directory, which overrides the path for the .env file. This inconsistency is addressed in +v1.28 by limiting the filepath to the project directory.