Apache Airflow AttributeError: 'NoneType' object has no attribute 'create_dagrun'

Question

I am trying to run a DAG in my local airflow environment which is connected to my Google Cloud Platform account, so I am able to create new GCP Virtual machine instances and configure them to process files from a staging area on a scheduled interval. As part of this I have to work with Custom Operators which inherits attributes from standard Airflow operators. When I import my first custom operator and run my DAG then it runs fine, however, if I try to import anymore custom operators then my DAG fails and gives the below image with the error message.

I would be grateful if someone could help me identify what could be going wrong here and share any helpful tips or checks to be made!

                          ____/ (  (    )   )  \___
                         /( (  (  )   _    ))  )   )\
                       ((     (   )(    )  )   (   )  )
                     ((/  ( _(   )   (   _) ) (  () )  )
                    ( (  ( (_)   ((    (   )  .((_ ) .  )_
                   ( (  )    (      (  )    )   ) . ) (   )
                  (  (   (  (   ) (  _  ( _) ).  ) . ) ) ( )
                  ( (  (   ) (  )   (  ))     ) _)(   )  )  )
                 ( (  ( \ ) (    (_  ( ) ( )  )   ) )  )) ( )
                  (  (   (  (   (_ ( ) ( _    )  ) (  )  )   )
                 ( (  ( (  (  )     (_  )  ) )  _)   ) _( ( )
                  ((  (   )(    (     _    )   _) _(_ (  (_ )
                   (_((__(_(__(( ( ( |  ) ) ) )_))__))_)___)
                   ((__)        \\||lll|l||///          \_))
                            (   /(/ (  )  ) )\   )
                          (    ( ( ( | | ) ) )\   )
                           (   /(| / ( )) ) ) )) )
                         (     ( ((((_(|)_)))))     )
                          (      ||\(|(|)|/||     )
                        (        |(||(||)||||        )
                          (     //|/l|||)|\\ \     )
                        (/ / //  /|//||||\\  \ \  \ _)
-------------------------------------------------------------------------------
Node: 0a1e098aa71f
-------------------------------------------------------------------------------
Traceback (most recent call last):
  File "/opt/python3.6/lib/python3.6/site-packages/flask/app.py", line 2317, in wsgi_app
    response = self.full_dispatch_request()
  File "/opt/python3.6/lib/python3.6/site-packages/flask/app.py", line 1840, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/opt/python3.6/lib/python3.6/site-packages/flask/app.py", line 1743, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/opt/python3.6/lib/python3.6/site-packages/flask/_compat.py", line 36, in reraise
    raise value
  File "/opt/python3.6/lib/python3.6/site-packages/flask/app.py", line 1838, in full_dispatch_request
    rv = self.dispatch_request()
  File "/opt/python3.6/lib/python3.6/site-packages/flask/app.py", line 1824, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/opt/python3.6/lib/python3.6/site-packages/flask_admin/base.py", line 69, in inner
    return self._run_view(f, *args, **kwargs)
  File "/opt/python3.6/lib/python3.6/site-packages/flask_admin/base.py", line 368, in _run_view
    return fn(self, *args, **kwargs)
  File "/opt/python3.6/lib/python3.6/site-packages/flask_login/utils.py", line 258, in decorated_view
    return func(*args, **kwargs)
  File "/usr/local/lib/airflow/airflow/www/utils.py", line 276, in wrapper
    return f(*args, **kwargs)
  File "/usr/local/lib/airflow/airflow/www/utils.py", line 323, in wrapper
    return f(*args, **kwargs)
  File "/usr/local/lib/airflow/airflow/utils/db.py", line 73, in wrapper
    return func(*args, **kwargs)
  File "/usr/local/lib/airflow/airflow/www/views.py", line 1180, in trigger
    store_serialized_dags=STORE_SERIALIZED_DAGS
  File "/usr/local/lib/airflow/airflow/utils/db.py", line 73, in wrapper
    return func(*args, **kwargs)
  File "/usr/local/lib/airflow/airflow/models/__init__.py", line 3005, in create_dagrun
    return self.get_dag(store_serialized_dags=store_serialized_dags).create_dagrun(
AttributeError: 'NoneType' object has no attribute 'create_dagrun'

Answer 1

Go to airflow_project/logs/scheduler and check the last logs