I use this a lot. It has served me very well. The code:


import hashlib
import functools

import markus  # optional
from django.core.cache import cache
from django import http
from django.utils.encoding import force_bytes, iri_to_uri

metrics = markus.get_metrics(__name__)  # optional


def json_response_cache_page_decorator(seconds):
    """Cache only when there's a healthy http.JsonResponse response."""

    def decorator(func):

        @functools.wraps(func)
        def inner(request, *args, **kwargs):
            cache_key = 'json_response_cache:{}:{}'.format(
                func.__name__,
                hashlib.md5(force_bytes(iri_to_uri(
                    request.build_absolute_uri()
                ))).hexdigest()
            )
            content = cache.get(cache_key)
            if content is not None:

                # metrics is optional
                metrics.incr(
                    'json_response_cache_hit',
                    tags=['view:{}'.format(func.__name__)]
                )

                return http.HttpResponse(
                    content,
                    content_type='application/json'
                )
            response = func(request, *args, **kwargs)
            if (
                isinstance(response, http.JsonResponse) and
                response.status_code in (200, 304)
            ):
                cache.set(cache_key, response.content, seconds)
            return response

        return inner

    return decorator

To use it simply add to Django view functions that might return a http.JsonResponse. For example, something like this:


@json_response_cache_page_decorator(60)
def search(request):
    q = request.GET.get('q')
    if not q:
        return http.HttpResponseBadRequest('no q')
    results = search_database(q)
    return http.JsonResponse({
        'results': results,
    })

The reasons I use this instead of django.views.decorators.cache.cache_page() is because of a couple of reasons.

  • cache_page generates cache keys that don't contain the view function name.
  • cache_page tries to cache the whole http.HttpResponse instance which can't be serialized if you use the msgpack serializer.
  • cache_page also sends Cache-Control headers which is not always what you want.
  • Not possible to inject your own custom code such as my usage of metrics.

Disclaimer: This snippet of code comes from a side-project that has a very specific set of requirements. They're rather unique to that project and I have a full picture of the needs. E.g. I know what specific headers matter and don't matter. Your project might be different. For example, perhaps you don't have markus to handle your metrics. Or perhaps you need to re-write the query string for something to normalize the cache key differently. Point being, take the snippet of code as inspiration when you too find that django.views.decorators.cache.cache_page() isn't good enough for your Django view functions.

Comments

Your email will never ever be published.

Previous:
The best grep tool in the world; ripgrep June 19, 2018 Linux, Web development, macOS
Next:
To defer or to async JavaScript tags. That's the question. June 29, 2018 Web development, Web Performance, JavaScript
Related by category:
A Python dict that can report which keys you did not use June 12, 2025 Python
How I run standalone Python in 2025 January 14, 2025 Python
How to resolve a git conflict in poetry.lock February 7, 2020 Python
get in JavaScript is the same as property in Python February 13, 2025 Python
Related by keyword:
Welcome to the world django-fancy-cache! March 1, 2013 Python, Django
Custom CacheMiddleware that tells Javascript a page is cached in Django August 24, 2009 Django
Secs sell! How I cache my entire pages (server-side) May 10, 2012 Python, Django