cache the redirects in memory to not hit the database on every request

hostname_redirects/middleware.py

@@ -5,30 +5,36 @@
 from hostname_redirects.models import RedirectHost
 
 
+def _get_redirect(new_hostname, request):
+    new_location = '%s://%s%s' % (
+        request.is_secure() and 'https' or 'http',
+        new_hostname,
+        request.get_full_path()
+    )
+    return HttpResponsePermanentRedirect(new_location)
+
+
 class HostnameRedirectMiddleware(object):
     def process_request(self, request):
+        # cache all redirect hostnames in one query
+        if not hasattr(self, '_cache'):
+            self._cache = dict(
+                RedirectHost.objects.values_list('hostname', 'site__domain'))
         server_name = request.META['SERVER_NAME']
         try:
-            new_hostname = RedirectHost.objects.select_related('site') \
-                .get(hostname=server_name).site.domain
-        except RedirectHost.DoesNotExist:
+            return _get_redirect(self._cache[server_name], request)
+        except KeyError:
             if getattr(settings, 'REMOVE_WWW', None) \
                     and server_name.startswith('www.'):
-                new_hostname = server_name[4:]
-            else:
-                catchall = getattr(settings,
-                    'CATCHALL_REDIRECT_HOSTNAME', None)
-                # if catchall hostname is set, verify that the current
-                # hostname is valid, and redirect if not
-                if catchall and not Site.objects.filter(
-                        domain=server_name).exists():
-                    new_hostname = catchall
-                else:
-                    # either catchall is not set or current hostname is valid
-                    return None
-        new_location = '%s://%s%s' % (
-            request.is_secure() and 'https' or 'http',
-            new_hostname,
-            request.get_full_path()
-        )
-        return HttpResponsePermanentRedirect(new_location)
+                return _get_redirect(server_name[4:], request)
+            catchall = getattr(settings,
+                'CATCHALL_REDIRECT_HOSTNAME', None)
+            # if catchall hostname is set, verify that the current
+            # hostname is valid, and redirect if not
+            if catchall:
+                # cache all site domains in one query
+                if not hasattr(self, '_sites'):
+                    self._sites = Site.objects.values_list('domain', flat=True)
+                if server_name not in self._sites:
+                    return _get_redirect(catchall, request)
+        return None