FastAPI and Uvicorn Logging #python #fastapi #uvicorn #logging

README.md

FastAPI and Uvicorn Logging

When running FastAPI app, all the logs in console are from Uvicorn and they do not have timestamp and other useful information. As Uvicorn applies python logging module, we can override Uvicorn logging formatter by applying a new logging configuration.

Meanwhile, it's able to unify the your endpoints logging with the Uvicorn logging by configuring all of them in the config file log_conf.yaml.

Before overriding:

uvicorn main:app --reload

INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [34318] using StatReload
INFO:     Started server process [34320]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     127.0.0.1:50062 - "GET / HTTP/1.1" 200 OK

After applying log_conf.yaml:

uvicorn main:app --reload --log-config=log_conf.yaml

2023-03-08 15:40:41,170 - uvicorn.error - INFO - Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
2023-03-08 15:40:41,170 - uvicorn.error - INFO - Started reloader process [34322] using StatReload
2023-03-08 15:40:41,297 - asyncio - DEBUG - Using selector: EpollSelector
2023-03-08 15:40:41,432 - uvicorn.error - INFO - Started server process [34324]
2023-03-08 15:40:41,432 - uvicorn.error - INFO - Waiting for application startup.
2023-03-08 15:40:41,432 - uvicorn.error - INFO - Application startup complete.
2023-03-08 15:48:21,450 - main - INFO - request / endpoint!
2023-03-08 15:48:21,450 - uvicorn.access - INFO - 127.0.0.1:59782 - "GET / HTTP/1.1" 200

logs with FastAPI and Uvicorn · tiangolo/fastapi · Discussion #7457 · GitHub

Python Comprehensive Logging using YAML Configuration · GitHub

log_conf.yaml

version: 1
disable_existing_loggers: False
formatters:
  default:
    # "()": uvicorn.logging.DefaultFormatter
    format: '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
  access:
    # "()": uvicorn.logging.AccessFormatter
    format: '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
handlers:
  default:
    formatter: default
    class: logging.StreamHandler
    stream: ext://sys.stderr
  access:
    formatter: access
    class: logging.StreamHandler
    stream: ext://sys.stdout
loggers:
  uvicorn.error:
    level: INFO
    handlers:
      - default
    propagate: no
  uvicorn.access:
    level: INFO
    handlers:
      - access
    propagate: no
root:
  level: DEBUG
  handlers:
    - default
  propagate: no

main.py

from fastapi import FastAPI
import logging

logger = logging.getLogger(__name__)

app = FastAPI()

@app.get("/")
async def func():
    logger.info(f"request / endpoint!")
    return {"message": "hello world!"}

requirements.txt

uvicorn>=0.20.0
fastapi>=0.89.1
PyYAML>=6.0

If you only really care about logging some extra info for HTTP requests, I've found @app.middleware("http") to be the silver bullet. Excellent example at this SO answer.

Tank you so much for this!

In case you also want to use gunicorn, you just have to convert the conf to JSON and start gunicorn with --log-config-json log_conf.json.
The loggers for gunicorn are called:

"gunicorn.error": {
    "level": "INFO",
    "handlers": [
        "default"
    ],
    "propagate": "no"
},
"gunicorn.access": {
    "level": "INFO",
    "handlers": [
        "access"
    ],
    "propagate": "no"
}

It is very helpful, thanks a lot!