Rate-limit autocomplete widgets Ajax requests

[Federico Jaramillo Martínez]

The current implementation of the Ajax autocomplete widget using Select2 in Django triggers a request for every key-press. This creates unnecessary load on servers.

This patch rate-limit the requests by adding a delay using the ajax.delay option provided by Select2.

​https://github.com/django/django/pull/11695

[Federico Jaramillo Martínez]

Multiple consecutive request

[Federico Jaramillo Martínez]

Requests with a delay until user stops typing

[Federico Jaramillo Martínez]

Include link to PR

[Claude Paroz]

I cannot say for sure 500 is the good value, but some delay is definitely an improvement.

[Federico Jaramillo Martínez]

Updated the patch, tests are passing.

500 was the number that gave me the least amount of unnecessary requests while still giving a perception of responsiveness, but those were more or less empiric tests with some co-workers. More than 500 felt slow.

We found that less than 250 would start sending requests for slow typers.

Given that this would be a default, I proposed 500 as that was the higher acceptable number for us. If a specific site requires a lower delay, it can be overridden on a custom widget or by overriding resources/static/admin/js/autocomplete.js.

I thought that it would be more important to avoid unnecessary requests over the gain of 100ms in the admin area.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 8f686086:

Fixed #30722 -- Added default rate-limiting requests to admin's Select2 widget.