Ever wanted to add the time taken for a response to your API, so the client knows how long that takes?
I first noticed this cool feature on AWX, a management platform for ansible playbooks.

There’s response headers looked like this:

So I checked out their source code and copied how they did it:

In generics.py the package extends the base DRF ApiView class and adds a bit of stuff, the important stuff for us is:

    def finalize_response(self, request, response, *args, **kwargs):
        ...
        response = super().finalize_response(request, response, *args, **kwargs)
        time_started = getattr(self, 'time_started', None)
        response['X-API-Node'] = settings.CLUSTER_HOST_ID
        ...
        
    def initialize_request(self, request, *args, **kwargs):
        ...
        self.time_started = time.time()
        ...

So I created a class extending for ApiView:

class APIView(views.APIView):
    '''
    Add timing to the base APIView class
    '''
    def initialize_request(self, request, *args, **kwargs):
        self.time_started = time.time()
        return super().initialize_request(request, *args, **kwargs)
        
    def finalize_response(self, request, response, *args, **kwargs):
        response = super().finalize_response(request, response, *args, **kwargs)
        time_started = getattr(self, 'time_started', None)
        if time_started:
            time_elapsed = time.time() - self.time_started
            response['X-API-Time'] = '%0.3fs' % time_elapsed
        return response

Now all I needed to do was entend from my_package.ApiView instead of restframework.views.ApiView and I would get an X-API-Time header.

It worked well for a while, but then I needed to use more Generic Class Based Views (Which extend from ApiView)…check out CDRF. So I could just add these methods, to the extended versions of restframework.generics.ListCreateView etc.

But that just doesn’t feel right. Simply because I can see I am repeating myself multiple times. I just be able to define this functionality once and have all similar objects (those that extend from ApiView) have that functionality…

Using a Mixin to add the Time taken to Respond

I just created a mixin, by extracting those functions into a single class that inherits from nothing:

class TimedAPIMixin:
    def initialize_request(self, request, *args, **kwargs):
        self.time_started = time.time()
        return super().initialize_request(request, *args, **kwargs)

    def finalize_response(self, request, response, *args, **kwargs):
        response = super().finalize_response(request, response, *args, **kwargs)
        time_started = getattr(self, 'time_started', None)
        if time_started:
            time_elapsed = time.time() - self.time_started
            response['X-API-Time'] = '%0.3fs' % time_elapsed
        return response

Using them in the other views:

from rest_framework import views
from rest_framework import generics


class APIView(TimedAPIMixin, views.APIView):
    pass


class ListCreateAPIView(TimedAPIMixin, generics.ListCreateAPIView):
    pass


class ListAPIView(TimedAPIMixin, generics.ListAPIView):
    pass

It only works if the mixin is the first thing it inherits from, otherwise the first class will take preference.