news: cache the news details page for non-logged in users

Logged in users can edit the page so the content should not be cached,
for non-logged in users we are happy to cache this page in nginx.

main/utils.py

@@ -1,13 +1,15 @@
 import hashlib
 import pickle
 import re
+from functools import WRAPPER_ASSIGNMENTS, wraps
 
 import markdown
 from django.core.cache import cache
 from django.db import connections, router
 from django.http import HttpResponse
 from django.template.defaultfilters import slugify
 from django.utils.timezone import now
+from django.views.decorators.cache import cache_page
 from markdown.extensions import Extension
 from pgpdump.packet import SignaturePacket
 
@@ -62,6 +64,22 @@ def empty_response():
 make_choice = lambda l: [(str(m), str(m)) for m in l]   # noqa E741
 
 
+def cache_user_page(timeout):
+    '''Cache the page only for non-logged in users'''
+
+    def decorator(view_func):
+        @wraps(view_func, assigned=WRAPPER_ASSIGNMENTS)
+        def _wrapped_view(request, *args, **kwargs):
+            if request.user.is_authenticated:
+                return view_func(request, *args, **kwargs)
+            result = cache_page(
+                timeout,
+                key_prefix=(f"_auth_{request.user.is_authenticated}_"))
+            return result(view_func)(request, *args, **kwargs)
+        return _wrapped_view
+    return decorator
+
+
 def set_created_field(sender, **kwargs):
     '''This will set the 'created' field on any object to the current UTC time
     if it is unset.

news/urls.py

@@ -1,6 +1,8 @@
 from django.contrib.auth.decorators import permission_required
 from django.urls import path, re_path
 
+from main.utils import cache_user_page
+
 from .views import (
     NewsCreateView,
     NewsDeleteView,
@@ -21,7 +23,7 @@
     path('add/',
          permission_required('news.add_news')(NewsCreateView.as_view())),
     re_path(r'^(?P<slug>[-\w]+)/$',
-            NewsDetailView.as_view()),
+            cache_user_page(1831)(NewsDetailView.as_view())),
     re_path(r'^(?P<slug>[-\w]+)/edit/$',
             permission_required('news.change_news')(NewsEditView.as_view())),
     re_path(r'^(?P<slug>[-\w]+)/delete/$',