Middleware

Middleware is run around each request processing.

In Python we can display this as:

Outer(Middle(Inner(final_method)))(my param)

Each layer calls the next with the the same parameters as it was called with, and returns the same. This allows us to edit requests and responses globally with ease. Each layer of middleware can return e.g an error page without calling the next layer, so final_method is not guaranteed to be called.

Adding middleware

Adding middleware is done by modifying the project settings. See Settings for more information about this.

Creating your own

Creating your own middleware is quite easy. Let’s create a simple logging middleware as an example.

import logging

class LoggingMiddleware(object):
    def __init__(self, passthrough):
    self.logger = logging.getLogger()
    self.logger.addHandler(logging.FileHandler('/tmp/mylog.txt'))
    self.logger.setLevel(logging.DEBUG)
    self.passthrough = passthrough

def __call__(self, request):
    self.logger.debug('Got request %s', request)
    response = self.passthrough(request)
    self.logger.debug('Got response %s', response)
    return response

So, what’s going on here?

Every middleware must accept a passthrough parameter. This is the next method in the middleware chain (or the handler itself). In the __call__ method we accept a mandatory request parameter, and return the result of the passthrough-method, called with request as it’s parameter.