Best practice to run FastAPI on Cloud Run with server port as $PORT

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Example Code

"""
A sample Hello World server.
"""
import uvicorn

import os

from fastapi import FastAPI, Request
from fastapi.staticfiles import StaticFiles
from fastapi.templating import Jinja2Templates

app = FastAPI()
app.mount("/static", StaticFiles(directory="static"), name="static")
templates = Jinja2Templates(directory="templates")


@app.route('/')
def hello(request: Request):
    """Return a friendly HTTP greeting."""
    message = "It's running!"

    """Get Cloud Run environment variables."""
    service = os.environ.get('K_SERVICE', 'Unknown service')
    revision = os.environ.get('K_REVISION', 'Unknown revision')

    return templates.TemplateResponse('index.html', context={
        "request": request,
        "message": message,
        "Service": service,
        "Revision": revision})


if __name__ == "__main__":
    uvicorn.run("main:app", host="0.0.0.0", port=int(os.environ.get('PORT', 8000)), log_level="info")

Description

I’ve been using Google Cloud Code in VSCode and PyCharm and the example they have for Python is a Flask app. I’ve been trying to rewrite the example app but with FastAPI. To have it running on Cloud Run you have to start the server with the port binded to an OS env variable called PORT. My question is:

1. Should I start uvicorn programmaticaly like in the example or,
2. Should I have a “normal” FastAPI app main.py file and use the CMD or ENTRYPOINT to bind the $PORT variable?

Note: ENTRYPOINT ["uvicorn", "main:app", "-port", "$PORT"] won’t work because the CMD in exec form won’t substitute the variable to its value, as documented here. It must be in shell form ENTRYPOINT uvicorn main:app --port $PORT

Operating System

Linux

Operating System Details

No response

FastAPI Version

0.78.0

Python Version

Python 3.10.4

Additional Context

The Cloud Code Flask sample code: https://github.com/GoogleCloudPlatform/cloud-code-samples/tree/v1/python/cloud-run-python-hello-world

[Kludex]

Having multiple ways to achieve the same goal can be more confusing than helpful. 😅

[alexsantos]

Do not run uvicorn alone. Read this docs from their page. https://www.uvicorn.org/deployment/

They recommend to run it with gunicorn and to use UvicornWorker: “Run gunicorn -k uvicorn.workers.UvicornWorker for production”

From the FastAPI documentation:

My question is about how should I pass the $PORT variable to the server (uvicorn/gunicorn) not about the server itself to use.