How do I terminate a flask app that's running as a service?

Question

I was able to get my flask app running as a service thanks to Is it possible to run a Python script as a service in Windows? If possible, how?, but when it comes to stopping

Answer 1

You can stop the Werkzeug web server gracefully before you stop the Win32 server. Example:

from flask import request

def shutdown_server():
    func = request.environ.get('werkzeug.server.shutdown')
    if func is None:
        raise RuntimeError('Not running with the Werkzeug Server')
    func()

@app.route('/shutdown', methods=['POST'])
def shutdown():
    shutdown_server()
    return 'Server shutting down...'

If you add this to your Flask server you can then request a graceful server shutdown by sending a POST request to /shutdown. You can use requests or urllib2 to do this. Depending on your situation you may need to protect this route against unauthorized access.

Once the server has stopped I think you will have to no problem stopping the Win32 service.

Note that the shutdown code above appears in this Flask snippet.

Answer 2

You could also trick Flask into believing you pressed Ctrl + C:

def shutdown_flask(self):
    from win32api import GenerateConsoleCtrlEvent
    CTRL_C_EVENT = 0
    GenerateConsoleCtrlEvent(CTRL_C_EVENT, 0)

Then simply call shutdown_flask() in your SvcStop():

try:
    # try to exit gracefully
    self.shutdown_flask()
except Exception as e:
    # force quit
    os._exit(0)

Should shutdown_flask() fail for some reason, os._exit() makes sure your service will end (albeit with a nasty warning), by halting the interpreter.

Answer 3

I recommend you use http://supervisord.org/. Actually not work in Windows, but with Cygwin you can run supervisor as in Linux, including run as service.

For install Supervisord: https://stackoverflow.com/a/18032347/3380763

After install you must configure the app, here an example: http://flaviusim.com/blog/Deploying-Flask-with-nginx-uWSGI-and-Supervisor/ (Is not necessary that you use Nginx with the Supervisor's configuration is enough)