Gracefully Stop Flask App in Python: No Ctrl-C Needed

If you're working with Flask, you may have noticed that stopping the app can sometimes be a bit tricky. Normally, you would use Ctrl-C to stop the app, but this can cause some issues, especially if you're running the app in a production environment.

Fortunately, there's a simple solution to this problem. Instead of using Ctrl-C, you can use Flask's built-in signal handling to gracefully stop the app. Here's how:

├Źndice
  1. Step 1: Import the signal Module
  2. Step 2: Create a Signal Handler Function
  3. Step 3: Register the Signal Handler
  4. Step 4: Run Your Flask App

Step 1: Import the signal Module


import signal

This will allow us to handle signals in our Flask app.

Step 2: Create a Signal Handler Function


def signal_handler(signum, frame):
    print('Flask app is shutting down...')
    # Add any cleanup code here
    sys.exit(0)

This function will be called when a signal is received, allowing us to gracefully shut down our Flask app. You can add any cleanup code you need here, such as closing database connections or saving data.

Step 3: Register the Signal Handler


signal.signal(signal.SIGINT, signal_handler)

This will register our signal handler function to be called when a SIGINT signal is received. This is the signal that is sent when you press Ctrl-C.

Step 4: Run Your Flask App


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

Once you've registered your signal handler, you can simply run your Flask app as normal. When you want to stop the app, simply send a SIGINT signal by pressing Ctrl-C. Flask will catch the signal and call your signal handler function, allowing you to gracefully shut down the app.

Using signal handling to stop your Flask app is a simple and reliable solution that can help you avoid issues in production environments. By following these steps, you can ensure that your app shuts down cleanly and all necessary cleanup is performed.

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