How to use Flask-Script and Gunicorn

Question

I'm working on on a Flask app using Flask's built in dev server. I start it using Flask-Script. I want to switch to using Gunicorn as the web server. To do so, do I need to write some sort of integration code between Flask-Script and Gunicorn? Or is Flask-Script irrelevant to running the app using Gunicorn?

Thanks in advance!

Props to @sean-lynch. The following is working, tested code based on his answer. The changes I made were:

• Options that aren't recognized by Gunicorn are removed from sys.argv in remove_non_gunicorn_command_line_args() before trying to start the server. Otherwise Gunicorn throws an error with a message like this: error: unrecognized arguments: --port 5010. I remove -p because, even though it doesn't cause the error, that's only because Gunicorn thinks its the short form of its pidfile option, which is obviously not what's intended.

• GunicornServer.handle() signature modified to match the method it overrides i.e. Command.handle()

-

from flask_script import Command
from gunicorn.app.base import Application

class GunicornServer(Command):

    description = 'Run the app within Gunicorn'

    def __init__(self, host='127.0.0.1', port=8000, workers=6):

        self.port = port
        self.host = host
        self.workers = workers

    def get_options(self):
        return (
            Option('-t', '--host',
                   dest='host',
                   default=self.host),

            Option('-p', '--port',
                   dest='port',
                   type=int,
                   default=self.port),

            Option('-w', '--workers',
                   dest='workers',
                   type=int,
                   default=self.workers),
        )

    def handle(self, app, *args, **kwargs):

        host = kwargs['host']
        port = kwargs['port']
        workers = kwargs['workers']

        def remove_non_gunicorn_command_line_args():
            import sys
            args_to_remove = ['--port','-p']
            def args_filter(name_or_value):
                keep = not args_to_remove.count(name_or_value)
                if keep:
                    previous = sys.argv[sys.argv.index(name_or_value) - 1]
                    keep = not args_to_remove.count(previous)
                return keep
            sys.argv = filter(args_filter, sys.argv)

        remove_non_gunicorn_command_line_args()

        from gunicorn import version_info
        if version_info < (0, 9, 0):
            from gunicorn.arbiter import Arbiter
            from gunicorn.config import Config
            arbiter = Arbiter(Config({'bind': "%s:%d" % (host, int(port)),'workers': workers}), app)
            arbiter.run()
        else:
            class FlaskApplication(Application):
                def init(self, parser, opts, args):
                    return {
                        'bind': '{0}:{1}'.format(host, port),
                        'workers': workers
                    }

                def load(self):
                    return app

            FlaskApplication().run()

manager.add_command('gunicorn', GunicornServer())

Answer 1

As Dhaivat said, you can just use your Flask app directly with Gunicorn.

If you still want to use Flask-Script, you will need to create a custom Command. I don't have any experience with Gunicorn, but I found a similar solution for Flask-Actions and ported it to Flask-Script, although be warned, it's untested.

from flask_script import Command, Option

class GunicornServer(Command):

    description = 'Run the app within Gunicorn'

    def __init__(self, host='127.0.0.1', port=8000, workers=4):
        self.port = port
        self.host = host
        self.workers = workers

    def get_options(self):
        return (
            Option('-H', '--host',
                   dest='host',
                   default=self.host),

            Option('-p', '--port',
                   dest='port',
                   type=int,
                   default=self.port),

            Option('-w', '--workers',
                   dest='workers',
                   type=int,
                   default=self.workers),
        )

    def handle(self, app, host, port, workers):

        from gunicorn import version_info

        if version_info < (0, 9, 0):
            from gunicorn.arbiter import Arbiter
            from gunicorn.config import Config
            arbiter = Arbiter(Config({'bind': "%s:%d" % (host, int(port)),'workers': workers}), app)
            arbiter.run()
        else:
            from gunicorn.app.base import Application

            class FlaskApplication(Application):
                def init(self, parser, opts, args):
                    return {
                        'bind': '{0}:{1}'.format(host, port),
                        'workers': workers 
                    }

                def load(self):
                    return app

            FlaskApplication().run()

You can then either register it to replace Flask's local development server at python manage.py runserver

manager.add_command("runserver", GunicornServer())

or register as a new command such as python manage.py gunicorn

manager.add_command("gunicorn", GunicornServer())

Edit June 2016: With the latest version of Flask-Script, change the method handle with __call__. old flask-script vs new flask-script

Answer 2

I wrote a better version of GunicornServer based on Sean Lynch's, the command now accept all gunicorn's arguments

from yourapp import app
from flask.ext.script import Manager, Command, Option

class GunicornServer(Command):
    """Run the app within Gunicorn"""

    def get_options(self):
        from gunicorn.config import make_settings

        settings = make_settings()
        options = (
            Option(*klass.cli, action=klass.action)
            for setting, klass in settings.iteritems() if klass.cli
        )
        return options

    def run(self, *args, **kwargs):
        from gunicorn.app.wsgiapp import WSGIApplication

        app = WSGIApplication()
        app.app_uri = 'manage:app'
        return app.run()

manager = Manager(app)
manager.add_command("gunicorn", GunicornServer())