refactor: manage enforcer state within class when app is ready

Author: mariajgrimaldi

openedx_authz/apps.py

@@ -39,3 +39,9 @@ class OpenedxAuthzConfig(AppConfig):
             },
         },
     }
+
+    def ready(self):
+        """Initialization layer for the openedx_authz app."""
+        from openedx_authz.engine.enforcer import AuthzEnforcer
+        # Initialize the enforcer to ensure it's ready when the app starts
+        AuthzEnforcer()

openedx_authz/engine/enforcer.py

@@ -21,18 +21,48 @@
 from casbin import FastEnforcer
 from django.conf import settings
 
+from openedx_authz.engine import adapter
 from openedx_authz.engine.adapter import ExtendedAdapter
 from openedx_authz.engine.watcher import Watcher
 
 logger = logging.getLogger(__name__)
 
-adapter = ExtendedAdapter()
-enforcer = FastEnforcer(settings.CASBIN_MODEL, adapter, enable_log=True)
-enforcer.enable_auto_save(True)
 
-if Watcher:
-    try:
-        enforcer.set_watcher(Watcher)
-        logger.info("Watcher successfully set on Casbin enforcer")
-    except Exception as e:  # pylint: disable=broad-exception-caught
-        logger.error(f"Failed to set watcher on Casbin enforcer: {e}")
+class AuthzEnforcer:
+    """Singleton class to manage the Casbin FastEnforcer instance.
+
+    Ensures a single enforcer instance is created safely and configured with the
+    ExtendedAdapter and Redis watcher for policy management and synchronization.
+    """
+
+    enforcer = None
+
+    def __new__(cls):
+        """Singleton pattern to ensure a single enforcer instance."""
+        if cls.enforcer is None:
+            cls.enforcer = cls.initialize_enforcer()
+        return cls.enforcer
+
+    def initialize_enforcer(self) -> FastEnforcer:
+        """
+        Create and configure the Casbin FastEnforcer instance.
+
+        This function initializes the Casbin FastEnforcer with the ExtendedAdapter
+        for database-backed policy storage and sets up the Redis watcher for
+        real-time policy synchronization.
+
+        Returns:
+            FastEnforcer: Configured Casbin enforcer with adapter and watcher
+        """
+        adapter = ExtendedAdapter()
+        enforcer = FastEnforcer(settings.CASBIN_MODEL, adapter, enable_log=True)
+        enforcer.enable_auto_save(True)
+
+        if Watcher:
+            try:
+                enforcer.set_watcher(Watcher)
+                logger.info("Watcher successfully set on Casbin enforcer")
+            except Exception as e:  # pylint: disable=broad-exception-caught
+                logger.error(f"Failed to set watcher on Casbin enforcer: {e}")
+
+        return enforcer