Hello 🙋♂️,
Running a ⏩FastAPI ⏩ application in production is very easy and fast, but along the way some Uvicorn logs are lost.
In this article I will discuss how to write a custom UvicornWorker and to centralize your logging configuration into a single file.
To keep things as simple as possible I’ve put all my code in a single Python file.
main.py
import uvicorn as uvicorn
from fastapi import FastAPI, APIRouter
router = APIRouter(prefix="")
def create_app():
fast_app = FastAPI()
fast_app.include_router(router)
return fast_app
@router.get("/")
def read_root():
return {"Hello": "World"}
if __name__ == '__main__':
app = create_app()
uvicorn.run(app=app)
Running the code will return a {"Hello": "World"} json when you visit the root endpoint / at http://127.0.0.1:8000. 😁
When you check the console window, the following log lines are printed:
INFO: Started server process [10276] INFO: Waiting for application startup. INFO: Application startup complete. INFO: Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit) INFO: 127.0.0.1:53491 - "GET / HTTP/1.1" 200 OK
Notice the Uvicorn log GET / HTTP/1.1″ 200 OK.
According to Uvicorn’s deployment docs we should run Uvicorn in a production settings with the following command: gunicorn -k uvicorn.workers.UvicornWorker main:create_app.
(venv2) ➜ FastAPILogging gunicorn -k uvicorn.workers.UvicornWorker main:create_app [2021-05-17 22:10:44 +0300] [6250] [INFO] Starting gunicorn 20.1.0 [2021-05-17 22:10:44 +0300] [6250] [INFO] Listening at: http://127.0.0.1:8000 (6250) [2021-05-17 22:10:44 +0300] [6250] [INFO] Using worker: uvicorn.workers.UvicornWorker [2021-05-17 22:10:44 +0300] [6252] [INFO] Booting worker with pid: 6252 [2021-05-17 22:10:45 +0300] [6252] [WARNING] ASGI app factory detected. Using it, but please consider setting the --factory flag explicitly. [2021-05-17 22:10:45 +0300] [6252] [INFO] Started server process [6252] [2021-05-17 22:10:45 +0300] [6252] [INFO] Waiting for application startup. [2021-05-17 22:10:45 +0300] [6252] [INFO] Application startup complete.
Now, if we visit the root endpoint, the console won’t print “GET / HTTP/1.1” 200 OK anymore/ 🤦♂️.
To fix it we need a custom UvicornWorker ⚙ and a logging configuration file 🗃.
Create a new file and name it logging.yaml, then paste the following contents in it:
version: 1
disable_existing_loggers: false
formatters:
standard:
format: "%(asctime)s - %(levelname)s - %(message)s"
handlers:
console:
class: logging.StreamHandler
formatter: standard
stream: ext://sys.stdout
loggers:
uvicorn:
error:
propagate: true
root:
level: INFO
handlers: [console]
propagate: no
This file will configure our root logger and our Uvicorn logger. To read more on the topic please see Python logging configuration.
Next, we will create a custom UvicornWorker class that will set log_config to the path of our logging.yaml file, to pass the logging configuration that we’ve just made to Uvicorn. 🦄
I added the following code in main.py:
class MyUvicornWorker(UvicornWorker):
CONFIG_KWARGS = {
"log_config": "/mnt/c/Users/denis/PycharmProjects/FastAPILogging/logging.yaml",
}
▶ If we run the application with:
gunicorn -k main.MyUvicornWorker main:create_app
We should see the Uvicorn access logs printed in the console 🦄
(venv2) ➜ FastAPILogging gunicorn -k main.MyUvicornWorker main:create_app [2021-05-17 22:31:28 +0300] [6278] [INFO] Starting gunicorn 20.1.0 [2021-05-17 22:31:28 +0300] [6278] [INFO] Listening at: http://127.0.0.1:8000 (6278) [2021-05-17 22:31:28 +0300] [6278] [INFO] Using worker: main.MyUvicornWorker [2021-05-17 22:31:28 +0300] [6280] [INFO] Booting worker with pid: 6280 2021-05-17 22:31:28,185 - WARNING - ASGI app factory detected. Using it, but please consider setting the --factory flag explicitly. 2021-05-17 22:31:28,185 - INFO - Started server process [6280] 2021-05-17 22:31:28,185 - INFO - Waiting for application startup. 2021-05-17 22:31:28,185 - INFO - Application startup complete. 2021-05-17 22:31:30,129 - INFO - 127.0.0.1:54004 - "GET / HTTP/1.1" 200
Thanks for reading! 📚
requirements.txt
click==7.1.2 fastapi==0.65.1 gunicorn==20.1.0 h11==0.12.0 httptools==0.2.0 pydantic==1.8.2 PyYAML==5.4.1 starlette==0.14.2 typing-extensions==3.10.0.0 uvicorn==0.13.4 uvloop==0.15.2
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