librelist archives

Re: [flask] Running behind proxy with URL prefix other than /

From:

Peter Hansen

Date:

2010-07-21 @ 20:09

On 2010-07-21 1:47 PM, Simon Sapin wrote:
 > You could fix SCRIPT_NAME with a WSGI middleware :
[snip]

I had temporarily hacked a solution by subclassing the Flask app class 
and overriding request_context(), adjusting the environment before the 
_RequestContext was created from it.

After getting that working, I thought I'd try the middleware approach. 
I'd never written any before, but with your simple example as a guide it 
wasn't too hard.

Better yet, rather than specifying URL scheme and prefix from the 
command line, as I had been doing, I was able to pull the info 
automatically from headers I added in nginx.  Here's the solution:

The nice thing is that werkzeug.router.Map directly supported all this. 
The trick is simply figuring out how to arrange for the right 
environment to let it work.

class ReverseProxied(object):
     '''Wrap the application in this middleware and configure the 
front-end server
     to add these headers, to let you quietly bind this to a URL other 
than /
     and to an HTTP scheme that is different than what is used locally.

     In nginx:
         location /myprefix {
             proxy_pass http://192.168.0.1:5001;     # where Flask app runs
             proxy_set_header Host $host;
             proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
             proxy_set_header X-Scheme $scheme;
             proxy_set_header X-Script-Name /myprefix;
             }

     :param app: the WSGI application
     '''
     def __init__(self, app):
         self.app = app

     def __call__(self, environ, start_response):
         script_name = environ.get('HTTP_X_SCRIPT_NAME', '')
         if script_name:
             environ['SCRIPT_NAME'] = script_name
             path_info = environ['PATH_INFO']
             if path_info.startswith(script_name):
                 environ['PATH_INFO'] = path_info[len(script_name):]

         scheme = environ.get('HTTP_X_SCHEME', '')
         if scheme:
             environ['wsgi.url_scheme'] = scheme
         return self.app(environ, start_response)


Installed in app using:

    app = Flask(__name__)
    app.wsgi_app = ReverseProxied(app.wsgi_app)


Thanks for the nudge, Simon!

--
Peter

Le 21/07/2010 22:09, Peter Hansen a écrit :
> Here's the solution:
>    

Great! You could write a snippet so that others find it more easily than 
here : http://flask.pocoo.org/snippets/

The good thing with your solution is that it works with any WSGI app, 
not just Flask.

Regards,
-- 
Simon Sapin

On 2010-07-21 4:20 PM, Simon Sapin wrote:
> Great! You could write a snippet so that others find it more easily than
> here : http://flask.pocoo.org/snippets/
>
> The good thing with your solution is that it works with any WSGI app,
> not just Flask.

I suppose it does.  Well, let's just leave it in the Flask snippets page 
to give the site some more traffic, if Armin's provider can handle it. :)

See http://flask.pocoo.org/snippets/35/

(By the way, Armin, a Deployment category may be appropriate.)

--
Peter

Hi,

On 7/21/10 9:55 PM, Peter Hansen wrote:
> (By the way, Armin, a Deployment category may be appropriate.)
Added category and moved snippet.


Regards,
Armin