Sentry with Flask on AWS Lambda not capturing errors

Question

I've deployed a flask application on AWS lambda. To perform error tracking I want to integrate Sentry into the application. Here is my setup for the application

def _handle_error(e):
    code = 500
    msg = 'Not Found'

    if isinstance(e, HTTPException):
        code = 404
    elif isinstance(e, ValueError):
        msg = str(e)

    logging.exception(e)

    if os.getenv('SENTRY_DSN'):
        event_id = sentry_sdk.capture_exception(e)
        logging.info(f'Error event was sent to sentry, event id: {event_id}')

    return jsonify({'error': msg}), code


def create_app():
    app = Flask(__name__)
    CORS(app, support_credentials=True)

    if os.getenv('SENTRY_DSN'):
        sentry_logging = LoggingIntegration(
            level=logging.DEBUG,     # Capture info and above as breadcrumbs
            event_level=logging.ERROR  # Send errors as events
        )

        sentry_sdk.init(dsn=os.getenv('SENTRY_DSN'),
                        integrations=[FlaskIntegration(), sentry_logging])

    app.register_blueprint(bp_routes)

    app.register_error_handler(Exception, _handle_error)

I use the custom error handler in flask to be able to return a generic error message without any sensitive information. When capturing the error I'm trying to manually create an event in Sentry

event_id = sentry_sdk.capture_exception(e)

Running the the code locally with python application.py everything works, the event is created in Sentry with the expected values.

When deploying the same code to lambda the event is no longer generated.

Also when I remove the custom flask error handler

# app.register_error_handler(Exception, _handle_error)

and deploy it to lambda the event IS generated!

Why is it the capture_exception not working on lambda?

Answer 1

Using any web framework under AWS Lambda additionally requires the installation of the AWS Lambda integration

For services similar to AWS Lambda, the generic serverless integration might become useful.