stablum opened a new issue #19957:
URL: https://github.com/apache/airflow/issues/19957
### Apache Airflow version
2.2.2 (latest released)
### Operating System
Ubuntu 21.04 on a VM
### Versions of Apache Airflow Providers
root@AI-Research:~/learning_sets/airflow# pip freeze | grep
apache-airflow-providers
apache-airflow-providers-ftp==2.0.1
apache-airflow-providers-http==2.0.1
apache-airflow-providers-imap==2.0.1
apache-airflow-providers-sqlite==2.0.1
### Deployment
Other
### Deployment details
Airflow is at version 2.2.2
psql (PostgreSQL) 13.5 (Ubuntu 13.5-0ubuntu0.21.04.1)
The dag contains thousands of tasks for data download and preprocessing and
preparation which is destined to a mongodb database (so, I'm not using the
PostgreSQL inside my tasks).
### What happened
[2021-12-01 19:41:57,556] {scheduler_job.py:644} ERROR - Exception when
executing SchedulerJob._run_scheduler_loop
Traceback (most recent call last):
File "/usr/local/lib/python3.9/dist-packages/sqlalchemy/engine/base.py",
line 1276, in _execute_context
self.dialect.do_execute(
File
"/usr/local/lib/python3.9/dist-packages/sqlalchemy/engine/default.py", line
608, in do_execute
cursor.execute(statement, parameters)
psycopg2.errors.DeadlockDetected: deadlock detected
DETAIL: Process 322086 waits for ShareLock on transaction 2391367; blocked
by process 340345.
Process 340345 waits for AccessExclusiveLock on tuple (0,26) of relation
19255 of database 19096; blocked by process 340300.
Process 340300 waits for ShareLock on transaction 2391361; blocked by
process 322086.
HINT: See server log for query details.
CONTEXT: while updating tuple (1335,10) in relation "task_instance"
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File
"/usr/local/lib/python3.9/dist-packages/airflow/jobs/scheduler_job.py", line
628, in _execute
self._run_scheduler_loop()
File
"/usr/local/lib/python3.9/dist-packages/airflow/jobs/scheduler_job.py", line
709, in _run_scheduler_loop
num_queued_tis = self._do_scheduling(session)
File
"/usr/local/lib/python3.9/dist-packages/airflow/jobs/scheduler_job.py", line
792, in _do_scheduling
callback_to_run = self._schedule_dag_run(dag_run, session)
File
"/usr/local/lib/python3.9/dist-packages/airflow/jobs/scheduler_job.py", line
1049, in _schedule_dag_run
dag_run.schedule_tis(schedulable_tis, session)
File "/usr/local/lib/python3.9/dist-packages/airflow/utils/session.py",
line 67, in wrapper
return func(*args, **kwargs)
File "/usr/local/lib/python3.9/dist-packages/airflow/models/dagrun.py",
line 898, in schedule_tis
session.query(TI)
File "/usr/local/lib/python3.9/dist-packages/sqlalchemy/orm/query.py",
line 4063, in update
update_op.exec_()
File
"/usr/local/lib/python3.9/dist-packages/sqlalchemy/orm/persistence.py", line
1697, in exec_
self._do_exec()
File
"/usr/local/lib/python3.9/dist-packages/sqlalchemy/orm/persistence.py", line
1895, in _do_exec
self._execute_stmt(update_stmt)
File
"/usr/local/lib/python3.9/dist-packages/sqlalchemy/orm/persistence.py", line
1702, in _execute_stmt
self.result = self.query._execute_crud(stmt, self.mapper)
File "/usr/local/lib/python3.9/dist-packages/sqlalchemy/orm/query.py",
line 3568, in _execute_crud
return conn.execute(stmt, self._params)
File "/usr/local/lib/python3.9/dist-packages/sqlalchemy/engine/base.py",
line 1011, in execute
return meth(self, multiparams, params)
File "/usr/local/lib/python3.9/dist-packages/sqlalchemy/sql/elements.py",
line 298, in _execute_on_connection
return connection._execute_clauseelement(self, multiparams, params)
File "/usr/local/lib/python3.9/dist-packages/sqlalchemy/engine/base.py",
line 1124, in _execute_clauseelement
ret = self._execute_context(
File "/usr/local/lib/python3.9/dist-packages/sqlalchemy/engine/base.py",
line 1316, in _execute_context
self._handle_dbapi_exception(
File "/usr/local/lib/python3.9/dist-packages/sqlalchemy/engine/base.py",
line 1510, in _handle_dbapi_exception
util.raise_(
File "/usr/local/lib/python3.9/dist-packages/sqlalchemy/util/compat.py",
line 182, in raise_
raise exception
File "/usr/local/lib/python3.9/dist-packages/sqlalchemy/engine/base.py",
line 1276, in _execute_context
self.dialect.do_execute(
File
"/usr/local/lib/python3.9/dist-packages/sqlalchemy/engine/default.py", line
608, in do_execute
cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (psycopg2.errors.DeadlockDetected) deadlock
detected
DETAIL: Process 322086 waits for ShareLock on transaction 2391367; blocked
by process 340345.
Process 340345 waits for AccessExclusiveLock on tuple (0,26) of relation
19255 of database 19096; blocked by process 340300.
Process 340300 waits for ShareLock on transaction 2391361; blocked by
process 322086.
HINT: See server log for query details.
CONTEXT: while updating tuple (1335,10) in relation "task_instance"
[SQL: UPDATE task_instance SET state=%(state)s WHERE task_instance.dag_id =
%(dag_id_1)s AND task_instance.run_id = %(run_id_1)s AND task_instance.task_id
IN (%(task_id_1)s, %(task_id_2)s, %(task_id_3)s, %(task_id_4)s, %(task_id_5)s,
%(task_id_6)s, %(task_id_7)s, %(task_id_8)s, %(task_id_9)s, %(task_id_10)s,
%(task_id_11)s, %(task_id_12)s, %(task_id_13)s, %(task_id_14)s, %(task_id_15)s,
%(task_id_16)s, %(task_id_17)s, %(task_id_18)s, %(task_id_19)s, %(task_id_20)s)]
[parameters: {'state': <TaskInstanceState.SCHEDULED: 'scheduled'>,
'dag_id_1': 'download_and_preprocess_sets', 'run_id_1':
'manual__2021-12-01T17:31:23.684597+00:00', 'task_id_1': 'download_1379',
'task_id_2': 'download_1438', 'task_id_3': 'download_1363', 'task_id_4':
'download_1368', 'task_id_5': 'download_138', 'task_id_6': 'download_1432',
'task_id_7': 'download_1435', 'task_id_8': 'download_1437', 'task_id_9':
'download_1439', 'task_id_10': 'download_1457', 'task_id_11': 'download_168',
'task_id_12': 'download_203', 'task_id_13': 'download_782', 'task_id_14':
'download_1430', 'task_id_15': 'download_1431', 'task_id_16': 'download_1436',
'task_id_17': 'download_167', 'task_id_18': 'download_174', 'task_id_19':
'download_205', 'task_id_20': 'download_1434'}]
(Background on this error at: http://sqlalche.me/e/13/e3q8)
[2021-12-01 19:41:57,566] {local_executor.py:388} INFO - Shutting down
LocalExecutor; waiting for running tasks to finish. Signal again if you don't
want to wait.
[2021-12-01 19:42:18,013] {process_utils.py:100} INFO - Sending
Signals.SIGTERM to GPID 285470
[2021-12-01 19:42:18,105] {process_utils.py:66} INFO - Process
psutil.Process(pid=285470, status='terminated', exitcode=0, started='18:56:21')
(285470) terminated with exit code 0
[2021-12-01 19:42:18,106] {scheduler_job.py:655} INFO - Exited execute loop
### What you expected to happen
Maybe 24 concurrent processes/tasks are too many?
### How to reproduce
reproducibility is challenging, but maybe the exception provides enough info
for a fix
### Anything else
all the time, after some time the dag is being run
### Are you willing to submit PR?
- [ ] Yes I am willing to submit a PR!
### Code of Conduct
- [X] I agree to follow this project's [Code of
Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)
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