Logging Overview

Logging is an essential aspect of any application, providing valuable insights into its behavior and helping to identify and troubleshoot issues. In FastAPI, logging can be easily integrated to capture information about requests, responses, errors, and other relevant events. This guide will explore how to implement logging in your FastAPI applications.

Basic Logging

Import the Logging Module:

Python

import logging

Create a Logger:

Python

logger = logging.getLogger(name)

Log Messages:

Python

@app.get(“/”)
def read_root():
logger.info(“Received a GET request to /”)
return {“Hello”: “World”}

Configuring the Logger

To customize the logging behavior, you can configure the logger’s level, format, and handlers.

Set the Log Level:

Python

logger.setLevel(logging.DEBUG)

Create a Handler:

Python

handler = logging.StreamHandler()

Set the Handler’s Formatter:

Python

formatter = logging.Formatter(‘%(asctime)s – %(name)s – %(levelname)s – %(message)s’)
handler.setFormatter(formatter)

Add the Handler to the Logger:

Python

logger.addHandler(handler)

Logging Request and Response Information

To log details about incoming requests and outgoing responses, you can use the request and response objects provided by FastAPI.

Python

@app.get("/items/{item_id}")
def read_item(item_id: int, request: Request, response: Response):
    logger.info(f"Received GET request for item {item_id}")
    # ...
    logger.info(f"Sending response: {response.json()}")

Logging Exceptions

You can log exceptions using the try...except block:

Python

@app.get("/items/{item_id}")
def read_item(item_id: int):
    try:
        # ...
    except Exception as e:
        logger.error(f"Error reading item {item_id}: {e}")
        raise