Flask and Web.py both hang on atexit

Question

I have this simple Flask app: ``` from flask import Flask import prolog_handler as p app = Flask(__name__) app.debug = False @app.route('/') def hello(): for rule in p.rules: print rule return 'hello' if __name__ == '__main__': app.run(host='0.0.0.0', port=8080) ``` The prolog_handler module starts a session with a triplestore and loads some rules. It also has an atexit function that ends the session and prints a message like "Closing...". I start the server from the bash prompt with `python myapp.py`. Whenever I hit CTRL-C to stop the server, nothing happens. I don't get returned back to the bash prompt, and I don't see the "Closing..." message printed. I also tried to do this with Web.py with the same results. The that prolog_handler does is literally as simple as this: ``` tstore = openPrologSession() rules = ... def cleanUp(): print "Closing..." tstore.endSession() atexit.register(cleanUp) ``` So why is it so difficult to just perform an atexit task? PS: if I comment out all the s…

Accepted Answer

This may not be the perfect answer but I tried to use the following for Flask:

```
# These functions should be called when you tear down the application
app.teardown_functions = []

def teardown_applications(): 
    for func in app.teardown_functions:
       print('Calling teardown function %s' % func.__name__)
        func()

app.teardown_functions.append(function_tocall_at_exit)
```

This seems to work for me. I also tend to use gevent for all flask applications

```
if __name__ == '__main__':
    gevent.signal(signal.SIGINT, teardown_applications)
    http_server = WSGIServer(('', 5000), app)
    http_server.serve_forever()
```

This usually works for me.

Some of the module imports:

```
from flask import Flask
from gevent.wsgi import WSGIServer
import gevent
import signal

from gevent import monkey
monkey.patch_all()
```

Flask and Web.py both hang on atexit

Solution

Problem