SNOW-1465711: Add version_initializer callback (#1)

* SNOW-1465711: Add version_initializer callback

* Update setup.sql

* Update setup.sql

spcs-three-tier/app/manifest.yml

@@ -19,6 +19,9 @@ artifacts:
       - /spcs_app/napp/img_repo/eap_backend
       - /spcs_app/napp/img_repo/eap_router
 
+lifecycle_callbacks:
+    version_initializer: v1.init
+
 privileges:
   - BIND SERVICE ENDPOINT:
       description: "Ability to create ingress URLs."

spcs-three-tier/app/setup.sql

@@ -49,6 +49,23 @@ $$;
 
 GRANT USAGE ON PROCEDURE v1.get_configuration(STRING) TO APPLICATION ROLE app_admin;
 
+-- The version initializer callback is executed after a successful installation, upgrade, or downgrade of an application object.
+-- In case the application fails to upgrade, the version initializer of the previous (successful) version will be executed so you 
+-- can clean up application state that may have been modified during the failed upgrade.
+CREATE OR REPLACE PROCEDURE v1.init()
+RETURNS STRING 
+LANGUAGE SQL
+EXECUTE AS OWNER 
+AS
+$$
+BEGIN    
+    ALTER SERVICE IF EXISTS app_public.frontend FROM SPECIFICATION_FILE='frontend.yaml';
+    ALTER SERVICE IF EXISTS app_public.backend FROM SPECIFICATION_FILE='backend.yaml';
+    RETURN 'init complete';
+END $$;
+
+GRANT USAGE ON PROCEDURE v1.init() TO APPLICATION ROLE app_admin;
+
 CREATE OR REPLACE PROCEDURE v1.start_backend(pool_name VARCHAR)
     RETURNS string
     LANGUAGE sql