Invalidate cache when ApplicationGateway instance is saved

passbook/app_gw/apps.py

@@ -1,4 +1,6 @@
 """passbook Application Security Gateway app"""
+from importlib import import_module
+
 from django.apps import AppConfig
 
 
@@ -9,3 +11,6 @@ class PassbookApplicationApplicationGatewayConfig(AppConfig):
     label = 'passbook_app_gw'
     verbose_name = 'passbook Application Security Gateway'
     mountpoint = 'app_gw/'
+
+    def ready(self):
+        import_module('passbook.app_gw.signals')

passbook/app_gw/signals.py

@@ -0,0 +1,20 @@
+"""passbook app_gw cache clean signals"""
+
+from logging import getLogger
+
+from django.core.cache import cache
+from django.db.models.signals import post_save
+from django.dispatch import receiver
+
+from passbook.app_gw.middleware import IGNORED_HOSTNAMES_KEY
+from passbook.app_gw.models import ApplicationGatewayProvider
+
+LOGGER = getLogger(__name__)
+
+@receiver(post_save)
+# pylint: disable=unused-argument
+def invalidate_app_gw_cache(sender, instance, **kwargs):
+    """Invalidate Policy cache when app_gw is updated"""
+    if isinstance(instance, ApplicationGatewayProvider):
+        LOGGER.debug("Invalidating cache for ignored hostnames")
+        cache.delete(IGNORED_HOSTNAMES_KEY)