[WIP] Use WSGI server

[thaeli]

No description provided.

[kitsuta]

A bit over my head but it looks good to me!

[EliAndrewC]

Apologies for having missed this PR when it first dropped. I really love GMail's "important" / "not important" views but sometimes I'm a little too trusting that it didn't miss anything important and go for far too long without scrolling through and looking for things I need to check.

I'm unclear what the code in sideboard/server.py is accomplishing. We're already able to set the socket host and socket port (and I'm pretty sure the thread pool as well) without doing the unsubscribe / subscribe stuff. If there's something being accomplished by this then we should at least add some comments explaining why we're doing what we're doing there.

[EliAndrewC]

I probably need to delve into the cherrypy source code to figure out why we're doing this. Regardless, it would be useful to add a comment here explaining why. You have several comments explaining what you're doing, but I find "why" comments to be a lot more useful. In particular, "Unsubscribe the default server" doesn't tell me anything about the purpose of this code or what it's actually accomplishing. I'm pretty sure that we were already able to set server.socket_host and such in our config file, so I'm unclear what this code is doing.

[EliAndrewC]

Ok, so CherryPy has a poorly documented way to do this.

• There's a cherrypy.tree object
• ...which has an apps dictionary whose keys are the URL paths like '/uber'
• ...and whose values are usually cherrypy.Application objects
• ...which have a wsgiapp property
• ...which has a pipeline list
• ...which is a list of tuples of the names and classes of WSGI middleware.

Let's put that all together. First I'll define an example middleware:

from sideboard.lib import log

class TestMiddleware:
    def __init__(self, app):
        self.app = app

    def __call__(self, environ, start_response):
        log.error('TestMiddleware called with environ => {}', environ)
        return self.app(environ, start_response)

So let's say that we want to add that to the application which serves everything under /uber:

cherrypy.tree.apps['/uber'].wsgiapp.pipeline.append(('TestMiddleware', TestMiddleware))

Assuming you wanted to have a list of middleware that you automatically applied to all cherrypy applications which support it:

wsgi_middleware = [
    ('TestMiddleware', TestMiddleware)
]

def add_wsgi_middleware_to_cherrypy():
    for app in cherrypy.tree.apps.values():
        if hasattr(app, 'wsgiapp'):
            app.wsgiapp.pipeline.extend(wsgi_middleware)

add_wsgi_middleware_to_cherrypy()

I've tested this out for this test middleware, though I haven't tested any more advanced middlewares.