Configuring Logging for FastAPI Apps

Logging is an essential tool for debugging, monitoring, and troubleshooting FastAPI applications. It provides valuable insights into the application’s behavior, helping to identify and resolve issues efficiently. This guide will demonstrate how to configure logging for FastAPI applications, including setting log levels, using different handlers, and customizing log formats.

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

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, 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

Log exceptions using try...except blocks:

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

Additional Terms

• Logging Level: Adjust the log level based on your application’s needs (DEBUG, INFO, WARNING, ERROR, CRITICAL).
• Logging Format: Customize the format to include timestamps, thread IDs, and other relevant information.
• Logging Handlers: Use different handlers (file, email, database) for different logging scenarios.
• Structured Logging: Consider using structured logging formats (e.g., JSON) for easier parsing and analysis.
• Logging Libraries: Explore third-party libraries like uvicorn.logging for additional features.