Using Flask with CherryPy to serve static files

Question

First time using a web framework, hope to get advice on the correct approach.

My aim is to have a server which can return static files based on a url passed in. I use Flask as my web framework and I intent to use CherryPy as my web server. The web describes many ways of setting up Flask with CherryPy and I am not sure if I am doing it correctly.

Resources I have been using:

• http://rhodesmill.org/brandon/2011/wsgi-under-cherrypy/
• Flask, CherryPy and static content
• http://fgimian.github.io/blog/2012/12/08/setting-up-a-rock-solid-python-development-web-server/
• http://flask.pocoo.org/docs/quickstart/
• http://flask.pocoo.org/snippets/24/

A simplified version of my Flask app, test.py:

from flask import Flask
from flask import request
from flask import send_from_directory
import os

FOLDER='contents'
ROOT=os.path.abspath(os.path.join('.', FOLDER))

@app.route("/get")
def route_3():
    return flask.send_from_directory(os.path.join(ROOT, 'p01', 'p02'), 'file12.zip', as_attachment=True)

if __name__ == "__main__":
    app.config.update(DEBUG=True)
    app.run()

My script for to run CherryPy:

import os
import cherrypy
from test import app
from cherrypy import wsgiserver

def option_1():
    cherrypy.tree.graft(app, '/')

    # If I comment this out, the server works
    #cherrypy.tree.mount(None, '/', config={
    #        '/': {
    #                'tools.staticdir.on': True,
    #                'tools.staticdir.dir': app.static_folder
    #            },
    #    })

    cherrypy.config.update({'server.socket_port': 5000})

    cherrypy.engine.start()
    cherrypy.engine.block()


def option2():
    d = wsgiserver.WSGIPathInfoDispatcher({'/': app})
    server = wsgiserver.CherryPyWSGIServer(('127.0.0.1', 5000), d)
    try:
       server.start()
    except KeyboardInterrupt:
       server.stop()

 if __name__ == '__main__':
    #option_1()
    option_2()

I have two questions:

1. In terms of setting up CherryPy to run Flask, both option_1 and option_2 works, so what is the difference between the two?
2. It is recommended to have the web server serve the static files as opposed to the web framework. Am I doing this correctly? When I read the response header, the server is not ' Werkzeug', so I am assuming that the CherryPy server is sending it.

Answer 1

Option 1 is high-level CherryPy

option_1 actually uses the entirety of the CherryPy web framework (which their documentation refers to as the APPLICATION layer) to mount your WSGI application - plugins, tools, etc. can be utilized fully. To serve static files with CherryPy you would want to change your commented out code to be something like this:

cherrypy.tree.mount(None, '/static', config={
    '/': {
        'tools.staticdir.on': True,
        'tools.staticdir.dir': app.static_folder
    },
})

Option 2 is low-level CherryPy

option_2, on the other hand, simply makes use of CherryPy's WSGI server implementation (the CORE layer) to serve your Flask app - it does not use any of the more framework-like aspects of CherryPy. If you are fine with serving your static files through Flask's routing layer as well, you can even remove the WSGIPathInfoDispatcher middleware and directly mount app under the CherryPyWSGIServer. If you want CherryPy to manage the /static route serving then you will want to mount an instance of cherrypy.tools.staticdir.handler under the /static route, like so:

static_handler = tools.staticdir.handler(section='/', dir=app.static_folder)
d = wsgiserver.WSGIPathInfoDispatcher({'/': app, '/static': static_handler})

Answer 2

If you want to replace the development server provided inside Werkzeug, I use the following in Flask-Script to replace runserver(). This will however in __main__

def runserver():
    """
    Overwriting the Flask Script runserver() default.
    CherryPy is much more stable than the built-in Flask dev server
    """
    debug_app = DebuggedApplication(app, True)
    cherrypy.tree.graft(debug_app, '/')
    cherrypy.config.update({
        'engine.autoreload_on': True,
        'server.socket_port': 5000,
        'server.socket_host': '0.0.0.0'
    })
    try:
        cherrypy.engine.start()
        cherrypy.engine.block()
    except KeyboardInterrupt:
        cherrypy.engine.stop()

If you do not have DebuggedApplication wrapper the DEBUG = True will not work. You may need to adjust this slightly based on your application. It will also provide Ctrl+C

Joe