django request lifecycle

Django Request Lifecycle
Architecture for django application
We can divide the request life cycle of the django application into three layers.
1. Browser
2. Server
3. Django

1.Browser:

Browser(client) is responsible for sending data to the server and also responsible for receiving the response back.

2. Server:

  • It receives the request from the browser, based on the request it gives response back. If we take an example of NGINX server. It can handle the 10,000 requests in a second based on the resources of the server(RAM, Processor). 
  • If it receives more than  10,000 requests in a second it creates another process to handle it. 
  • We can divide request resources in two types.  
  • 1. static resource 
  • 2. dynamic resource(It has to process the data based on request to provide resource)
  • If browser request for the static resources like images/css/javascript/etc, then NGINX  serves the request without sending it to the uWSGI server.
  • If browser requests for a dynamic request then NGINX passes it to the uWSGI to process the request. 
  • At this stage NGINX acts like a reverse proxy server. A reverse proxy server is a type of proxy server that typically sits behind the firewall in a private network and directs browser/client requests to the appropriate back-end server(uWSGI).
  • Advantages of reverse proxy server are  Load balancing, Web acceleration, Security and anonymity.

 3. Django

  • Django layer comes into the picture when request passed from nGINX to the uWSGI it  takes the request middlewares from the settings and applies on the request to modify request.
  • After applying the request middlewares it sends the request to url dispatcher. Url dispatcher is responsible for dispatching the request to a view based on the url pattern
  • Here we implement the business logic. We access the database resources by writing Django Queries.
  • The query passes to the ORM(Object Relation Mapper). ORM converts the django query into SQL(Structured Query Language) query and hits the database (MySQL/Postgres,etc). Database returns the query results in a relational table. ORM again converts these relational data into django queryset and returns back to the view.
  • View passes the context(data that's retrieved from the database) to the template.
  • Template renders the content with context data and forms the Response(HTML/XML/JSON/etc.) 
  • Again response middlewares which are defined in settings will apply and modifies the request and sends the response to the Browser(Client).

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