ephraimbuddy opened a new pull request #18975:
URL: https://github.com/apache/airflow/pull/18975
Using multiple schedulers causes Deadlock in _process_executor_events.
This PR fixes it.
The error:
```
[2021-10-14 08:37:18,377: INFO/ForkPoolWorker-1] Celery task ID:
6e8e34d/persistence.py", line 995, in _emit_update_statements
statement, multiparams
File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py",
line 1011, in execute
return meth(self, multiparams, params)
File "/usr/local/lib/python3.6/site-packages/sqlalchemy/sql/elements.py",
line 298, in _execute_on_connection
return connection._execute_clauseelement(self, multiparams, params)
File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py",
line 1130, in _execute_clauseelement
distilled_params,
File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py",
line 1317, in _execute_context
e, statement, parameters, cursor, context
File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py",
line 1511, in _handle_dbapi_exception
sqlalchemy_exception, with_traceback=exc_info[2], from_=e
File "/usr/local/lib/python3.6/site-packages/sqlalchemy/util/compat.py",
line 182, in raise_
raise exception
File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py",
line 1257, in _execute_context
cursor, statement, parameters, context
File
"/usr/local/lib/python3.6/site-packages/sqlalchemy/dialects/postgresql/psycopg2.py",
line 912, in do_executemany
cursor.executemany(statement, parameters)
sqlalchemy.exc.OperationalError: (psycopg2.errors.DeadlockDetected) deadlock
detected
DETAIL: Process 35678 waits for ShareLock on transaction 150292; blocked by
process 58800.
Process 58800 waits for ShareLock on transaction 150291; blocked by process
58799.
Process 58799 waits for ShareLock on transaction 150289; blocked by process
35678.
HINT: See server log for query details.
CONTEXT: while updating tuple (11,54) in relation "task_instance"
[SQL: UPDATE task_instance SET external_executor_id=%(external_executor_id)s
WHERE task_instance.task_id = %(task_instance_task_id)s AND
task_instance.dag_id = %(task_instance_dag_id)s AND task_instance.run_id =
%(task_instance_run_id)s]
[parameters: ({'external_executor_id':
'fe1c200a-ca4a-49b2-b5f9-ea53d5ed0846', 'task_instance_task_id':
'test_sensor_15', 'task_instance_dag_id': 'airflow_bug',
'task_instance_run_id': 'manual__2021-10-14T08:17:18.387618+00:00'},
{'external_executor_id': '1ee3e79a-ceab-4215-94cb-100d8de73bad',
'task_instance_task_id': 'test_sensor_22', 'task_instance_dag_id':
'airflow_bug', 'task_instance_run_id':
'manual__2021-10-14T08:17:18.387618+00:00'}, {'external_executor_id':
'8873162e-519f-4ef2-890c-d38754760c81', 'task_instance_task_id':
'test_sensor_24', 'task_instance_dag_id': 'airflow_bug',
'task_instance_run_id': 'manual__2021-10-14T08:17:18.387618+00:00'},
{'external_executor_id': '52d05186-5297-4079-b94a-132bef845673',
'task_instance_task_id': 'test_sensor_27', 'task_instance_dag_id':
'airflow_bug', 'task_instance_run_id':
'manual__2021-10-14T08:17:18.387618+00:00'}, {'external_executor_id':
'1e47d3a0-4398-4f07-9ebd-73e16ffa02ec', 'task_instance_task_id':
'test_sensor_28', 'task_ins
tance_dag_id': 'airflow_bug', 'task_instance_run_id':
'manual__2021-10-14T08:17:18.387618+00:00'}, {'external_executor_id':
'1c89c6e0-8cb6-437b-9ee5-56968bb993fc', 'task_instance_task_id':
'test_sensor_35', 'task_instance_dag_id': 'airflow_bug',
'task_instance_run_id': 'manual__2021-10-14T08:17:18.387618+00:00'})]
(Background on this error at: http://sqlalche.me/e/13/e3q8)
```
I tested the fix with 3 schedulers and it works.
How to reproduce:
Using 2 schedulers and celery executor, run this dag:
[dags.zip](https://github.com/apache/airflow/files/7345217/dags.zip)
One scheduler will stop with errors like the above after some time.
---
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