How to Execute Initialization Code Only Once During Django Server Startup?

Initialization Code Execution in Django at Startup

In Django, executing code only once during startup can be a common requirement. Let's explore a solution that ensures the code is executed only during the initial server startup, not on subsequent requests.

Initially, the solution proposed in the linked question raised the "Hello world" message twice in the terminal. The problem lies in the use of the MiddlewareNotUsed exception to terminate the middleware's execution.

Starting with Django 1.7, a dedicated hook has been introduced to address this issue. By overriding the ready method in your app's AppConfig class, you can specify startup-only code. This approach is cleaner and more explicit than using middleware.

For Django versions prior to 1.7, placing the startup code in the __init__.py file of one of your INSTALLED_APPS has proven effective. This code will be executed when the application is first loaded, ensuring that it runs only once.

Here is an example of the code placement for this approach:

# myapp/__init__.py
import your_module

your_module.initializer()

Take note that when using the ./manage.py runserver command, the initialization code might be executed twice due to internal server validation processes. However, in typical deployment scenarios or during automatic reloads by runserver, the code will execute only once.

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