[jira] [Created] (AIRFLOW-860) Circular module dependency prevents loading of custom executor plugin

["Nick Ivanov (JIRA)" <ji...@apache.org>]

Nick Ivanov created AIRFLOW-860:
-----------------------------------

             Summary: Circular module dependency prevents loading of custom executor plugin
                 Key: AIRFLOW-860
                 URL: https://issues.apache.org/jira/browse/AIRFLOW-860
             Project: Apache Airflow
          Issue Type: Bug
          Components: executor, plugins
    Affects Versions: Airflow 1.8
         Environment: Linux RHEL 7.6, Python 2.7.13
            Reporter: Nick Ivanov


Custom plugins cannot be loaded, which prevents airflow from running, due to apparent cyclic dependency in plugins_manager called in {{executors.\_\_init\_\_}} -- the top-level {{\_\_init\_\_}} attempts to load the default executor, which then goes back to plugins_manager etc.

{noformat}
  File "/usr/lib/python2.7/site-packages/airflow-1.9.0dev0_apache.incubating-py2.7.egg/EGG-INFO/scripts/airflow", line 17, in <module>
    from airflow import configuration
  File "/usr/lib/python2.7/site-packages/airflow-1.9.0dev0_apache.incubating-py2.7.egg/airflow/__init__.py", line 31, in <module>
    from airflow.models import DAG
  File "/usr/lib/python2.7/site-packages/airflow-1.9.0dev0_apache.incubating-py2.7.egg/airflow/models.py", line 62, in <module>
    from airflow.executors import DEFAULT_EXECUTOR, LocalExecutor
  File "/usr/lib/python2.7/site-packages/airflow-1.9.0dev0_apache.incubating-py2.7.egg/airflow/executors/__init__.py", line 55, in <module>
    raise AirflowException("Executor {0} not supported.".format(_EXECUTOR))
airflow.exceptions.AirflowException: Executor TestExecutor not supported.
{noformat}

While attempting {{from airflow.plugins_manager import executors_modules}} cycles right back where it came from:

{noformat}
>>> from airflow.plugins_manager import executor_modules
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/site-packages/airflow-1.9.0dev0_apache.incubating-py2.7.egg/airflow/__init__.py", line 31, in <module>
    from airflow.models import DAG
  File "/usr/lib/python2.7/site-packages/airflow-1.9.0dev0_apache.incubating-py2.7.egg/airflow/models.py", line 62, in <module>
    from airflow.executors import DEFAULT_EXECUTOR, LocalExecutor
  File "/usr/lib/python2.7/site-packages/airflow-1.9.0dev0_apache.incubating-py2.7.egg/airflow/executors/__init__.py", line 55, in <module>
    raise AirflowException("Executor {0} not supported.".format(_EXECUTOR))
airflow.exceptions.AirflowException: Executor LSFExecutor not supported.
{noformat}

To reproduce:

# Create a custom executor, e.g. by copying {{local_executor.py}} into {{$AIRFLOW_HOME/plugins/test_executor.py}} and replacing occurrences of "Local" with "Test" in the code, which will produce {{TestExecutor}}
# Update {{$AIRFLOW_HOME/airflow.cfg}} by setting in the {{\[core\]}} section: {{executor = TestExecutor}}
# Run any airflow command, e.g. "airflow version"



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