Vitor Baptista created AIRFLOW-1063:
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Summary: A manually-created DAG run can prevent a scheduled run to
be created
Key: AIRFLOW-1063
URL: https://issues.apache.org/jira/browse/AIRFLOW-1063
Project: Apache Airflow
Issue Type: Improvement
Components: scheduler
Affects Versions: Airflow 1.7.1.3
Reporter: Vitor Baptista
I manually created a DAG Run with the {{execution_date}} as {{2017-03-01
00:00:00}} on a monthly-recurrent DAG. After a while, I noticed that the
scheduled run was never created and checked the scheduler's logs, finding this
traceback:
{quote}
Process Process-475397:
Traceback (most recent call last):
File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
self.run()
File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
self._target(*self._args, **self._kwargs)
File "/usr/local/lib/python2.7/dist-packages/airflow/jobs.py", line 664, in
_do_dags
dag = dagbag.get_dag(dag.dag_id)
File "/usr/local/lib/python2.7/dist-packages/airflow/models.py", line 188, in
get_dag
orm_dag = DagModel.get_current(root_dag_id)
File "/usr/local/lib/python2.7/dist-packages/airflow/models.py", line 2320,
in get_current
obj = session.query(cls).filter(cls.dag_id == dag_id).first()
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py", line
2690, in first
ret = list(self[0:1])
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py", line
2482, in __getitem__
return list(res)
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py", line
2790, in __iter__
return self._execute_and_instances(context)
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py", line
2811, in _execute_and_instances
close_with_result=True)
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py", line
2820, in _get_bind_args
**kw
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py", line
2802, in _connection_from_session
conn = self.session.connection(**kw)
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line
966, in connection
execution_options=execution_options)
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line
971, in _connection_for_bind
engine, execution_options)
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line
382, in _connection_for_bind
self._assert_active()
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line
276, in _assert_active
% self._rollback_exception
InvalidRequestError: This Session's transaction has been rolled back due to a
previous exception during flush. To begin a new transaction with this Session,
first issue Session.rollback(). Original exception was:
(psycopg2.IntegrityError)
duplicate key value violates unique constraint
"dag_run_dag_id_execution_date_key"
DETAIL: Key (dag_id, execution_date)=(nct, 2017-03-01 00:00:00) already exists.
[SQL: 'INSERT INTO dag_run (dag_id, execution_date, start_date, end_date,
state, run_id, external_trigger, conf) VALUES (%(dag_id)s, %(execution_date)s,
%(start_date)s, %(end_date)s, %(state)s, %(run_id)s, %(external_trigger)s,
%(conf)s)
RETURNING dag_run.id'] [parameters: {'end_date': None, 'run_id':
u'scheduled__2017-03-01T00:00:00', 'execution_date': datetime.datetime(2017, 3,
1, 0, 0), 'external_trigger': False, 'state': u'running', 'conf': None,
'start_date': dateti
me.datetime(2017, 4, 3, 13, 48, 39, 168456), 'dag_id': 'nct'}]
{quote}
The problem is that the {{dag_runs}} table require the {{(dag_id,
execution_date)}} pair to be unique, so the scheduler was stuck in a loop where
it tried creating a new scheduled dag run but failed, as I had already created
one on the same {{execution_date}}. This was surprising. As a user, I would
expect that it would either schedule the run normally, even if there's a manual
one on the same date, or maybe it would skip that execution date.
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