paste.recursive – internal requests

Middleware to make internal requests and forward requests internally.

When applied, several keys are added to the environment that will allow you to trigger recursive redirects and forwards.

paste.recursive.include:

When you call environ['paste.recursive.include'](new_path_info) a response will be returned. The response has a body attribute, a status attribute, and a headers attribute.

paste.recursive.script_name:

The SCRIPT_NAME at the point that recursive lives. Only paths underneath this path can be redirected to.

paste.recursive.old_path_info:

A list of previous PATH_INFO values from previous redirects.

Raise ForwardRequestException(new_path_info) to do a forward (aborting the current request).

Module Contents

class paste.recursive.RecursiveMiddleware(application, global_conf=None)

A WSGI middleware that allows for recursive and forwarded calls. All these calls go to the same ‘application’, but presumably that application acts differently with different URLs. The forwarded URLs must be relative to this container.

Interface is entirely through the paste.recursive.forward and paste.recursive.include environmental keys.

paste.recursive.ForwardRequestException(url=None, environ={}, factory=None, path_info=None)

Used to signal that a request should be forwarded to a different location.

url

The URL to forward to starting with a / and relative to RecursiveMiddleware. URL fragments can also contain query strings so /error?code=404 would be a valid URL fragment.

environ

An altertative WSGI environment dictionary to use for the forwarded request. If specified is used instead of the url_fragment

factory

If specifed factory is used instead of url or environ. factory is a callable that takes a WSGI application object as the first argument and returns an initialised WSGI middleware which can alter the forwarded response.

Basic usage (must have RecursiveMiddleware present) :

from paste.recursive import ForwardRequestException
def app(environ, start_response):
    if environ['PATH_INFO'] == '/hello':
        start_response("200 OK", [('Content-type', 'text/plain')])
        return [b'Hello World!']
    elif environ['PATH_INFO'] == '/error':
        start_response("404 Not Found", [('Content-type', 'text/plain')])
        return [b'Page not found']
    else:
        raise ForwardRequestException('/error')

from paste.recursive import RecursiveMiddleware
app = RecursiveMiddleware(app)

If you ran this application and visited /hello you would get a Hello World! message. If you ran the application and visited /not_found a ForwardRequestException would be raised and the caught by the RecursiveMiddleware. The RecursiveMiddleware would then return the headers and response from the /error URL but would display a 404 Not found status message.

You could also specify an environ dictionary instead of a url. Using the same example as before:

def app(environ, start_response):
    ... same as previous example ...
    else:
        new_environ = environ.copy()
        new_environ['PATH_INFO'] = '/error'
        raise ForwardRequestException(environ=new_environ)

Finally, if you want complete control over every aspect of the forward you can specify a middleware factory. For example to keep the old status code but use the headers and resposne body from the forwarded response you might do this:

from paste.recursive import ForwardRequestException
from paste.recursive import RecursiveMiddleware
from paste.errordocument import StatusKeeper

def app(environ, start_response):
    if environ['PATH_INFO'] == '/hello':
        start_response("200 OK", [('Content-type', 'text/plain')])
        return [b'Hello World!']
    elif environ['PATH_INFO'] == '/error':
        start_response("404 Not Found", [('Content-type', 'text/plain')])
        return [b'Page not found']
    else:
        def factory(app):
            return StatusKeeper(app, status='404 Not Found', url='/error')
        raise ForwardRequestException(factory=factory)

app = RecursiveMiddleware(app)