Try using a pidfile

BookingSystem/app.py

@@ -129,12 +129,12 @@ def debug_login() -> flask.Response:
 
     init_db()
     Settings.verify_settings_exist()
+    start_routine()
 
     return app
 
 
 app = create_app()
 
 if __name__ == '__main__':
-    start_routine()
     app.run(host='0.0.0.0')

BookingSystem/routine_tasks.py

@@ -43,6 +43,13 @@ def start_routine():
         logger.info("Skipping routine tasks in testing environment")
         return
 
+    if os.path.exists('/tmp/feideutstyrbase.pid'):
+        with open('/tmp/feideutstyrbase.pid', 'r') as f:
+            pid = int(f.read())
+        if os.getpid() != pid:
+            logger.info("Skipping routine tasks on worker process")
+            return
+
     def _task(job_func):
         try:
             job_func()

entrypoint.sh

@@ -10,7 +10,7 @@ run_app() {
     cp -r /overrides/* /app;
   fi
 
-  gunicorn --bind 0.0.0.0:5000 -t 60 --preload routine_tasks:start_routine() app:app  &
+  gunicorn --bind 0.0.0.0:5000 -t 60 -p /tmp/feideutstyrbase.pid app:app &
   PID=$!
   wait $PID
 }