Fix django-compress caching issues

django-compress doesn't work well with cache. If horizon is
deployed in a containarized environment with pre-built static
in images, django-compress tries to load old templates from cache.

This patch introduces following changes:

* update_angular_template_hash uses the correct Django cache backend now
* fixed cache cleanup for memcached backend
* added clean_angular_template_cache management command to clean cache
  manually without executing heavy 'compress' command.

Closes-Bug: #1874657
Change-Id: If1fd61fa2e4b36e22797b0f54ac067a2a937f369

horizon/cache.py

@@ -0,0 +1,33 @@
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from django.conf import settings
+from django.core.cache import caches
+from django.core.cache.utils import make_template_fragment_key
+
+
+def cleanup_angular_template_cache(theme):
+    # The compressor has modified the angular template cache preloads
+    # which are cached in the 'COMPRESS_CACHE_BACKEND' Django cache.
+    django_cache = caches[settings.COMPRESS_CACHE_BACKEND]
+
+    # generate the same key as used in _scripts.html when caching the
+    # preloads
+    key = make_template_fragment_key(
+        "angular",
+        ['template_cache_preloads', theme]
+    )
+
+    # if template preloads have been cached, clear them
+    if django_cache.get(key):
+        # Set to None because memcached doesn't remove records immediately
+        django_cache.set(key, None)

horizon/templatetags/angular.py

@@ -15,11 +15,11 @@
 
 from compressor.signals import post_compress
 from django.contrib.staticfiles import finders
-from django.core.cache import caches
-from django.core.cache.utils import make_template_fragment_key
 from django.dispatch import receiver
 from django import template
 
+from horizon import cache
+
 register = template.Library()
 
 
@@ -37,21 +37,8 @@ def update_angular_template_hash(sender, **kwargs):
     compressed = context['compressed']  # the compressed content
     compressed_name = compressed['name']  # name of the compressed content
     if compressed_name == 'angular_template_cache_preloads':
-        # The compressor has modified the angular template cache preloads
-        # which are cached in the 'default' Django cache. Fetch that cache.
-        cache = caches['default']
-
-        # generate the same key as used in _scripts.html when caching the
-        # preloads
         theme = context['THEME']  # current theme being compressed
-        key = make_template_fragment_key(
-            "angular",
-            ['template_cache_preloads', theme]
-        )
-
-        # if template preloads have been cached, clear them
-        if cache.get(key):
-            cache.delete(key)
+        cache.cleanup_angular_template_cache(theme)
 
 
 @register.filter(name='angular_escapes')

openstack_dashboard/management/commands/cleanup_angular_template_cache.py

@@ -0,0 +1,24 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from django.conf import settings
+from django.core.management.base import BaseCommand
+
+from horizon import cache
+
+
+class Command(BaseCommand):
+    help = 'Clears template cache for angularized views.'
+
+    def handle(self, *args, **options):
+        for theme in settings.AVAILABLE_THEMES:
+            cache.cleanup_angular_template_cache(theme[0])

releasenotes/notes/cleanup-cache-command-64a5020755c5e05c.yaml

@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    Added an ``cleanup_angular_template_cache`` management command, that clears
+    template cache for angularized views. The command is available
+    as ``./manage.py cleanup_angular_template_cache``.
+fixes:
+  - |
+    [`bug/1874657 <https://bugs.launchpad.net/horizon/1874657>`_] Horizon
+    container upgrade works without additional ``./manage.py compress`` call.