cat /var/log/postgresql/postgresql-11-main.log.1|grep -B1 -A1 'logical'

2021-07-30 02:04:19.361 AST [971] LOG:  background worker "pgsentinel" (PID 22722) exited with exit code 1
2021-07-30 02:04:19.793 AST [30658] postgres@db_master LOG:  logical decoding found initial consistent point at DDB/7EE1D998
2021-07-30 02:04:19.793 AST [30658] postgres@db_master DETAIL:  Waiting for transactions (approximately 4) older than 3507682729 to end.
2021-07-30 02:04:19.793 AST [30658] postgres@db_master STATEMENT:  SELECT pg_create_logical_replication_slot('db_master_slot', 'pgoutput');
2021-07-30 02:04:20.008 AST [30658] postgres@db_master LOG:  logical decoding found consistent point at DDB/7EE34F78
2021-07-30 02:04:20.008 AST [30658] postgres@db_master DETAIL:  There are no old transactions anymore.
2021-07-30 02:04:20.008 AST [30658] postgres@db_master STATEMENT:  SELECT pg_create_logical_replication_slot('db_master_slot', 'pgoutput');
2021-07-30 02:04:21.370 AST [23080] LOG:  starting bgworker pgsentinel
--
2021-07-30 03:12:25.808 AST [971] LOG:  background worker "pgsentinel" (PID 2585) exited with exit code 1
2021-07-30 03:12:25.939 AST [648] postgres@db_master LOG:  logical decoding found initial starting point at DDB/DCEF2D80
2021-07-30 03:12:25.939 AST [648] postgres@db_master DETAIL:  Waiting for transactions (approximately 12) older than 3508856238 to end.
2021-07-30 03:12:25.939 AST [648] postgres@db_master STATEMENT:  SELECT pg_create_logical_replication_slot('db_master_slot', 'pgoutput');
2021-07-30 03:12:27.812 AST [2933] LOG:  starting bgworker pgsentinel
--
2021-07-30 03:14:17.022 AST [971] LOG:  background worker "pgsentinel" (PID 14812) exited with exit code 1
2021-07-30 03:14:17.084 AST [648] postgres@db_master LOG:  logical decoding found initial consistent point at DDB/E0F94960
2021-07-30 03:14:17.084 AST [648] postgres@db_master DETAIL:  Waiting for transactions (approximately 7) older than 3508891651 to end.
2021-07-30 03:14:17.084 AST [648] postgres@db_master STATEMENT:  SELECT pg_create_logical_replication_slot('db_master_slot', 'pgoutput');
2021-07-30 03:14:19.026 AST [15144] LOG:  starting bgworker pgsentinel
--
2021-07-30 03:16:44.807 AST [409] LOG:  starting bgworker pgsentinel
2021-07-30 03:16:46.046 AST [648] postgres@db_master LOG:  logical decoding found consistent point at DDB/E35A1B38
2021-07-30 03:16:46.046 AST [648] postgres@db_master DETAIL:  There are no old transactions anymore.
2021-07-30 03:16:46.046 AST [648] postgres@db_master STATEMENT:  SELECT pg_create_logical_replication_slot('db_master_slot', 'pgoutput');
2021-07-30 03:16:46.664 AST [409] ERROR:  backend with pid=405 not found