Revision history [back]

1. Setup a logger: To capture Flask's log message in a file during production, you should set up a logger. A logger provides an interface between your code and the logging system.

2. Choose a log level: You should choose a log level that is appropriate for your application. Log levels range from DEBUG (most verbose) to FATAL (least verbose).

3. Configure the logger: You should configure the logger to write to a file. You can set the file path, format, and other settings.

4. Test the logger: You should test the configuration of the logger by running your application and verifying that log messages are being written to the file.

5. Monitor the log: You should monitor the log file during production to ensure that your application is running smoothly. Look for error messages and other warnings that could indicate problems with the application.

6. Rotate and archive logs: You should consider rotating and archiving your log files periodically to ensure that they don't become too large and to preserve historical log data.

Here is an example code snippet to setup Flask's logger to write to a file:

import logging
from logging.handlers import RotatingFileHandler
from flask import Flask

app = Flask(__name__)

# Set the log level
app.logger.setLevel(logging.DEBUG)

# Set up a rotating file handler
handler = RotatingFileHandler('app.log', maxBytes=10000, backupCount=1)
handler.setLevel(logging.DEBUG)

# Set up the log formatter
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(formatter)

# Add the handler to the app logger
app.logger.addHandler(handler)

# Test the logger
app.logger.debug('This is a test log message')