如何在docker-compose.yml中有条件地运行不同的配置？

Question

I have configured SSL via certbot on live server. I have a volume mapping for this in nginx section of docker-compose.yml :

volumes:
  ...
  - /etc/letsencrypt:/etc/letsencrypt

This works just fine on the live server but I have a different setup on my local machine, where I run the app and see it on http://localhost . I suppose I don't need SSL on my local machine, so probably I just can exclude this part of setup if it runs locally.

Also this case makes me think I will have to potentially configure some other things differently locally vs live.

So, the question is how to properly distinguish these differences between local and live setups and apply them (semi)automatically depending on the environment?

Answer 1

Environment variables are typically a good way to create simple runtime portability like this, and many tools/apps/packages support runtime configuration by nothing more than environment variables. Unfortunately, nginx is not one of those apps

For nginx, try something like this:

environment:
  - NGINX_CONF=localhost.conf

Here, localhost.conf would be your nginx configuration for your local machine. Run an entrypoint.sh of some kind, and symlink the config specified by NGINX_CONF to wherever nginx will pick it up (usually /etc/nginx/conf.d or /etc/nginx/sites-enabled).

ln -s /etc/nginx/conf.d/running.conf /app/nginx-confs/${NGINX_CONF}

This assumes you have all of your confs copied to the container in /app/nginx-confs, but they can live wherever you like. The localhost.conf would serve your site as http://localhost .

For your live server, pass NGINX_CONF=liveserver.conf. This conf would serve https://www.liveserver.com or whatever you host is.

At this point, you can choose which nginx configuration you'll run when you start your container, using environment variables. Even if you don't want to do it this way, hopefully it gets you moving in the right direction and thinking about environment variables as a way to configure at runtime.

---

There are other, more granular ways of managing nginx confs at runtime. Something like confd or a templating engine like the mustache templating engine are options. There are roundabout ways in nginx with env directive and set_by_lua , but this feels like the most hacky solution to me so I prefer the others.

Answer 2

You can write a Makefile to generate different docker-compose.yml files depending on your needs.

Makefile:

# Makefile
-include config.mk

A_CONFIG_VAR ?= default_value

all: docker-compose.yml

docker-compose.yml: docker-compose.yml.in config.mk
        @echo 'Generating docker-compose.yml'
        @sed -e 's|@@A_CONFIG_VAR@@|$(A_CONFIG_VAR)|g' $< > $@

config.mk: put your configuration variables in this file.

# config.mk
A_CONFIG_VAR = "a_value"

docker-compose.yml.in: write an input docker-compose.yml file like so

volumes:
  - /path/to/somewhere:@@A_CONFIG_VAR@@

Change the contents of config.mk to suit your needs. And then run

make

This should generate a docker-compose.yml file for you.