Way to pass arguments to FastAPI app via command line

Question

I'm using python 3.8.0 for my FastAPI app. It uses .env file located on the root of a project directory. I am using dotenv package and location of the .env file is hardcoded within the app. This is my unit file

[Unit]
Description=Gunicorn instance for my_app
After=network.target

[Service]
User=nginx
Group=nginx
WorkingDirectory=/usr/share/nginx/html/my_app/
Environment="PATH=/usr/share/nginx/html/my_app/venv/bin"
ExecStart=/usr/share/nginx/html/my_app/venv/bin/gunicorn --bind unix:/usr/share/nginx/html/my_app/my_app.sock -w 4 -k uvicorn.workers.UvicornWorker app.main:app

[Install]
WantedBy=multi-user.target

Challenge is I want to run 2 versions (production and test) of the same app using 2 different .env on 2 different ports. I'll have to create second unit file. But how can I pass the name of 2 different env file name to the app for further usage. These files contain database connections and etc. I imagine it roughly like this 1st unit file

ExecStart=/usr/share/nginx/html/my_app/venv/bin/gunicorn 
--bind unix:/usr/share/nginx/html/my_app/my_app.sock -w 4 -k uvicorn.workers.UvicornWorker app.main:app --env_file_name=".env.prod"

2nd unit file

ExecStart=/usr/share/nginx/html/my_app/venv/bin/gunicorn 
--bind unix:/usr/share/nginx/html/my_app/my_app.sock -w 4 -k uvicorn.workers.UvicornWorker app.main:app --env_file_name=".env.dev"

Answer 1

You can set the path from which systemd will read the environment for your process exactly in unit file configuration. The setting is called EnvironmnetFile= . Just set the option to the path for .env.prod in one unit file and for the path to .env.test for another.