Flask Integration

Lumberjack provides deep integration with Flask applications through automatic instrumentation, request tracing, and error handling.

Installation

# Install with Flask support
uv add 'lumberjack_sdk[flask]'

Basic Setup

from flask import Flask
from lumberjack_sdk import Lumberjack, LumberjackFlask
import logging

app = Flask(__name__)

# Initialize Lumberjack first
Lumberjack.init(project_name="my-flask-app")

# Auto-instrument Flask
LumberjackFlask.instrument(app)

@app.route('/')
def hello():
    logging.info("Hello endpoint called")
    return "Hello, World!"

if __name__ == '__main__':
    app.run(debug=True)

What Gets Instrumented

When you call LumberjackFlask.instrument(app), Lumberjack automatically adds:

Request Tracing

• Start/end of each request
• HTTP method, URL, status code
• Request duration and response size

Error Handling

• Automatic exception capture
• Stack traces with local variables
• Request context for errors

Manual Logging

Use the built-in python library:

from flask import request, g
import logging

@app.route('/users/<int:user_id>')
def get_user(user_id):
    logging.info(f"Getting user {user_id} from {request.remote_addr}")

    try:
        user = User.query.get(user_id)
        if not user:
            logging.warning(f"User {user_id} not found")
            return "User not found", 404

        logging.info(f"User retrieved: {user.username}")
        return user.to_dict()

    except Exception as e:
        logging.error(f"Failed to get user {user_id}: {e}", exc_info=True)
        return "Internal server error", 500

Next Steps

• FastAPI Integration - FastAPI-specific guide
• Configuration Reference - All configuration options
• OpenTelemetry Integration - Production observability