How To Run Uvicorn In Heroku?

So I have figured out how to code a fastAPI and I am ready to deploy my script to heroku that I have worked with fastAPI (https://fastapi.tiangolo.com/) however the problem is that

Solution 1:

The answer(s) are correct, but to use FastAPI in production running as WSGI with ASGI workers is a better choice here is why, i ran a benchmark for this question, so here is the results.

Gunicorn with Uvicorn workers

Requests per second:8665.48 [#/sec] (mean)Concurrency Level:500Time taken for tests:0.577secondsComplete requests:5000Time per request:57.700 [ms] (mean)

Pure Uvicorn

Requests per second:3200.62 [#/sec] (mean)Concurrency Level:500Time taken for tests:1.562secondsComplete requests:5000Time per request:156.220 [ms] (mean)

As you can see there is a huge difference in RPS(Request per second) and response time for each request.

Procfiles

Gunicorn with Uvicorn Workers

web: gunicorn -w 4 -k uvicorn.workers.UvicornWorker main:app

Pure uvicorn

web: uvicorn main:app --workers 4

Solution 2:

I've tested your setup and after some checking (never used Heroku before) I'm guessing your uvicorn never binds to the appointed port (was the heroku-cli command heroku local working for you?)

Your Procfile could look like this;

web: uvicorn src.main:app --host=0.0.0.0 --port=${PORT:-5000}

This example assumes you have your source code within a subfolder named 'src' which has an empty __init__.py (indicating a Python module, you probably want to add src to the PYTHONPATH instead, see app.json) and main.py containing your fastapi app;

import socket
import sys

from fastapi import FastAPI

app = FastAPI()

hostname = socket.gethostname()

version = f"{sys.version_info.major}.{sys.version_info.minor}"@app.get("/")asyncdefread_root():
    return {
        "name": "my-app",
        "host": hostname,
        "version": f"Hello world! From FastAPI running on Uvicorn. Using Python {version}"
    }

I have added my working example to github which you can view on heroku (for now)

Solution 3:

You can also configure your FastAPI to run on Gunicorn with uvicorn as worker process. Following is the command line you can keep in the Procfile used by Heroku to make your app up and running. The below command will spin up your app on 3 worker processes

web: gunicorn -w 3 -k uvicorn.workers.UvicornWorker main:app

For detailed step by step video you can visit this video tutorial that details how to deploy FastAPI on Heroku in just 6 minutes. or you can have a detailed walkthrough of how to create and deploy python based FastAPI on Heroku from this blog post.

Solution 4:

By comparision, than pure uvicorn, uvicornworkers process much faster and this makes FastAPI to execute processes much faster than Flask.

In production, it suggestible to use guincorn with Uvicornworkers

In heroku Procfile,

web: gunicorn -k uvicorn.workers.UvicornWorker --bind 0.0.0.0:$PORT main:app

$PORT: instead of taking fixed port, it is preferred to use dynamic port.

Solution 5:

In my case I hadn't updated the wsgi app to be an asgi app.

when running:

gunicorn pm.wsgi --log-level=debug \
-k uvicorn.workers.UvicornWorker --log-file - --timeout 60

I got:

So, I added the WSGIMiddleware:

import os

from django.core.wsgi import get_wsgi_application
from dj_static import Cling
from uvicorn.middleware.wsgi import WSGIMiddleware
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "pm.settings")

# added the WSGIMiddleWare wrapper
application = WSGIMiddleware(Cling(get_wsgi_application()))