Anybody has seen such error and has hints what it could be?


 Dec 12 06:34:42 gefinal app/web.2 Error during __repr__ of Participant: 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: (raised as a result of Query-invoked autoflush; consider using a session.no_autoflush block if this flush is occurring prematurely)\n(psycopg2.errors.DeadlockDetected) deadlock detected\nDETAIL:  Process 910 waits for ShareLock on transaction 6006; blocked by process 102.\nProcess 102 waits for ShareLock on transaction 6005; blocked by process 910.\nHINT:  See server log for query details.\nCONTEXT:  while updating tuple (35,1) in relation "otree_participant"\n\n[SQL: UPDATE otree_participant SET _monitor_note=%(_monitor_note)s WHERE otree_participant.id = %(otree_participant_id)s]\n[parameters: ({\'_monitor_note\': \'P12\', \'otree_participant_id\': 1}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 3}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 4}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 10}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 13}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 16}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 18}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 19}  ... displaying 10 of 12 total bound parameter sets ...  {\'_monitor_note\': \'P12\', \'otree_participant_id\': 28}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 30})]\n(Background on this error at: http://sqlalche.me/e/13/e3q8)')
Dec 12 06:34:42 gefinal app/web.2 Error during __repr__ of Participant: 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: (raised as a result of Query-invoked autoflush; consider using a session.no_autoflush block if this flush is occurring prematurely)\n(psycopg2.errors.DeadlockDetected) deadlock detected\nDETAIL:  Process 910 waits for ShareLock on transaction 6006; blocked by process 102.\nProcess 102 waits for ShareLock on transaction 6005; blocked by process 910.\nHINT:  See server log for query details.\nCONTEXT:  while updating tuple (35,1) in relation "otree_participant"\n\n[SQL: UPDATE otree_participant SET _monitor_note=%(_monitor_note)s WHERE otree_participant.id = %(otree_participant_id)s]\n[parameters: ({\'_monitor_note\': \'P12\', \'otree_participant_id\': 1}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 3}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 4}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 10}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 13}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 16}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 18}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 19}  ... displaying 10 of 12 total bound parameter sets ...  {\'_monitor_note\': \'P12\', \'otree_participant_id\': 28}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 30})]\n(Background on this error at: http://sqlalche.me/e/13/e3q8)')
Dec 12 06:34:42 gefinal app/web.2 Error during __repr__ of Participant: 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: (raised as a result of Query-invoked autoflush; consider using a session.no_autoflush block if this flush is occurring prematurely)\n(psycopg2.errors.DeadlockDetected) deadlock detected\nDETAIL:  Process 910 waits for ShareLock on transaction 6006; blocked by process 102.\nProcess 102 waits for ShareLock on transaction 6005; blocked by process 910.\nHINT:  See server log for query details.\nCONTEXT:  while updating tuple (35,1) in relation "otree_participant"\n\n[SQL: UPDATE otree_participant SET _monitor_note=%(_monitor_note)s WHERE otree_participant.id = %(otree_participant_id)s]\n[parameters: ({\'_monitor_note\': \'P12\', \'otree_participant_id\': 1}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 3}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 4}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 10}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 13}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 16}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 18}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 19}  ... displaying 10 of 12 total bound parameter sets ...  {\'_monitor_note\': \'P12\', \'otree_participant_id\': 28}, {\'_monitor_note\': \'P12\', \'otree_participant_id\': 30})]\n(Background on this error at: http://sqlalche.me/e/13/e3q8)')

Did this affect any participant ? Did it only occur once or multiple times?

The first time it affected some participants. The next time it was not there. Now, I got it again when it affected only of one participant and the error looked slightly different (see attached).

Were you running multiple web dynos? That could cause this. This type of error should not occur because oTree runs in a single thread so there should not be deadlocks.

I am using 1 Performance-M web dyno

Actually, I have autoscaling on. So it might be this, I will try without that. Thanks!