Control the "main" exposed port with a $PORT variable

[erikgaal]

👉 Describe the problem

Deploying any image on Heroku requires you to have the web process listen on a port defined by the $PORT environment variable.

The web process must listen for HTTP traffic on $PORT, which is set by Heroku. EXPOSE in Dockerfile is not respected, but can be used for local testing. Only HTTP requests are supported.

1. https://devcenter.heroku.com/articles/container-registry-and-runtime#dockerfile-commands-and-runtime

👥 Problem evidence & reach

Anyone trying to deploy on services like Heroku that need you to run your Docker services on a controlled $PORT.

🏆 How to solve this problem

Have a way to control the port that the fpm-apache, fpm-nginx and fpm-unit image variants use to run the main web process.

♾️ My own workaround

I've added this in my own Dockerfile to get it to work sort of...

ENV PORT=8080
ENV NGINX_PORT=$PORT

RUN sed -i 's/8080/\$NGINX_PORT/g' /etc/nginx/site-opts.d/http.conf.template

I'm aware this is somewhat related to this discussion, but that didn't have the resolution I seek. :(