Created
April 2, 2021 19:59
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Django middleware to cache request.user
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| from django.contrib.auth import SESSION_KEY | |
| from django.core.cache import cache | |
| from django.utils.functional import SimpleLazyObject | |
| from django.contrib.auth.signals import user_logged_out | |
| from django.contrib.auth import get_user_model | |
| from django.db.models.signals import post_save, post_delete | |
| from functools import partial | |
| # Cache key for this middleware. | |
| CACHE_KEY = "cached_user_middleware:%s" | |
| class CachedUserMiddleware: | |
| """ | |
| Middleware that caches the authenticated user. If the user is not in the | |
| cache, it will fall-back to the original next user (`request.user`, which | |
| is assumed to be a `SimpleLazyObject` as well). | |
| This middleware must come after the session middleware and any other | |
| middleware that (potentially) modifies `request.user`. | |
| Implementation based on | |
| https://github.com/ui/django-cached_authentication_middleware | |
| """ | |
| def __init__(self, get_response=None): | |
| self.get_response = get_response | |
| self.request = None | |
| # Register signals. | |
| post_save.connect(self.on_user_save, sender=get_user_model()) | |
| post_delete.connect(self.on_user_deleted, sender=get_user_model()) | |
| user_logged_out.connect(self.on_user_logged_out) | |
| def __call__(self, request): | |
| """ | |
| Invoke middleware. | |
| It will overwrite `request.user` with `SimpleLazyObject`, so that it | |
| will only hit the cache if the user object is actually accessed. If | |
| the user is not in the cache, the original `request.user` is | |
| considered. It is assumed that this is a `SimpleLazyObject` as well. | |
| """ | |
| self.request = request | |
| request.user = SimpleLazyObject( | |
| partial(self.get_cached_user, request.user) | |
| ) | |
| return self.get_response(request) | |
| def on_user_save(self, *args, **kwargs): | |
| """ | |
| Invalidate the cached user (if set) when the user model is updated. | |
| """ | |
| user = kwargs["instance"] | |
| if self.request is not None: | |
| if user.id == self.request.user.id: | |
| self.delete_cached_user() | |
| def on_user_deleted(self, *args, **kwargs): | |
| """ | |
| Invalidate the cached user (if set) when the user model is deleted. | |
| """ | |
| user = kwargs["instance"] | |
| if self.request is not None: | |
| if user.id == self.request.user.id: | |
| self.delete_cached_user() | |
| def on_user_logged_out(self, *args, **kwargs): | |
| """ | |
| Invalidate the cached user (if set) when the user logout signal is | |
| received. | |
| """ | |
| if self.request is not None: | |
| self.delete_cached_user() | |
| def delete_cached_user(self): | |
| """ | |
| Delete the user from the cache. | |
| """ | |
| key = CACHE_KEY % self.request.session[SESSION_KEY] | |
| cache.delete(key) | |
| def get_cached_user(self, next_user): | |
| """ | |
| Try to get the user from the cache, or return the `next_user`. | |
| """ | |
| if not hasattr(self.request, "_cached_user"): | |
| key = CACHE_KEY % self.request.session[SESSION_KEY] | |
| try: | |
| user = cache.get(key) | |
| except KeyError: | |
| user = None | |
| if user is None: | |
| user = next_user | |
| # Cache authenticated users only. | |
| if getattr(user, "is_authenticated", False): | |
| cache.set(key, user) | |
| self.request._cached_user = user | |
| return self.request._cached_user |
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