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Django: Request/Response Cycle


Django Request Life Cycle 


A web application or a website revolves around the request-response cycle and Django applications are no exception to this. But it is not just a two step process. Our Django applications needs to go through various stages to return the end user some result. To understand the Django framework better we must understand how the requests are initiated and the end result is served to the end user.




When setting up a new Django project, one of the first things you’ll do is wire up your URLconfs and set up some views. But what’s actually happening under the hood here? How does Django route traffic to the view, and what part do middlewares play in this cycle?


Layers of Django Application

  • Request Middlewares
  • URL Router(URL Dispatcher)
  • Views
  • Context Processors
  • Template Renderers
  • Response Middlewares


Whenever a request comes in first it goes to the web server (Ngnix /Apache) . The the request goes to django's WSGI(Web Server Gateway Interface) /ASGI (Asynchronous Server Gateway Interface) .

WSGI / ASGI: is a specification where describes how a web server communicate with web applications and how web application can be chained together to process on request. WSGI uses GUNICORN implementation. And if we are running asynchronous servers then it would be ASGI and it will use UVICORN/Hypercorn

WSGI/ASGI translate the requests into something that our django application can understand. Then it is handled by the Request middlewares. We can have multiple middlewares. we can find it in project settings(settings.py). Django request middlewares follows the order while processing the request. Suppose if we have request middlewares in the order A, B, C then the request first processed by the middleware A and then B and then C. Django comes up with bunch of default middlewares. We can also write our own or custom middlewares. After request processed by the middlewares it will be submitted to the URL Router or URL dispatcher.

URL Router will take the request from the request middleware and it takes the URL Path from the request. Based on the url path URL router will tries to match the request path with the available URL patterns. These URL patterns are in the form of regular expressions. After matching the URL path with available URL patterns the request will be submitted to the View which is associated with the URL.

Now, we are in business logic layer Views. Views processes the business logic using request and request data(data sent in GET, POST, etc). After processing the request in the view the request is sent context processors, by using the request context processors adds the context data that will help Template Renderers to render the template to generate the HTTP response.

Again the request will send back to the Response middlewares to process it. Response middlewares will process the request and adds or modifies the header information/body information before sending it back to the client(Browser). After the browser will process and display it to the end user.


Post Credit: Sarthak Kumar 

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