Hi, I have reviewed the v21 patch. And found an issue.
Initially I started the standby server with a new postgresql.conf file (not the default postgresql.conf that is present in the instance). pg_ctl -D ../standby start -o "-c config_file=/new_path/postgresql.conf" And I have made 'max_replication_slots = 1' in new postgresql.conf and made 'max_replication_slots = 0' in the default postgresql.conf file. Now when we run pg_createsubscriber on standby we get error: pg_createsubscriber: error: could not set replication progress for the subscription "pg_createsubscriber_5_242843": ERROR: cannot query or manipulate replication origin when max_replication_slots = 0 NOTICE: dropped replication slot "pg_createsubscriber_5_242843" on publisher pg_createsubscriber: error: could not drop publication "pg_createsubscriber_5" on database "postgres": ERROR: publication "pg_createsubscriber_5" does not exist pg_createsubscriber: error: could not drop replication slot "pg_createsubscriber_5_242843" on database "postgres": ERROR: replication slot "pg_createsubscriber_5_242843" does not exist I observed that when we run the pg_createsubscriber command, it will stop the standby instance (the non-default postgres configuration) and restart the standby instance which will now be started with default postgresql.conf, where the 'max_replication_slot = 0' and pg_createsubscriber will now fail with the error given above. I have added the script file with which we can reproduce this issue. Also similar issues can happen with other configurations such as port, etc. The possible solution would be 1) allow to run pg_createsubscriber if standby is initially stopped . I observed that pg_logical_createsubscriber also uses this approach. 2) read GUCs via SHOW command and restore them when server restarts I would prefer the 1st solution. Thanks and Regards, Shlok Kyal
sudo pkill -9 postgres rm -rf ../primary ../standby ../new_path rm -rf primary.log standby.log ./initdb -D ../primary cat << EOF >> ../primary/postgresql.conf wal_level = 'logical' EOF ./pg_ctl -D ../primary -l primary.log start ./psql -d postgres -c "CREATE table t1 (c1 int);" ./psql -d postgres -c "Insert into t1 values(1);" ./psql -d postgres -c "Insert into t1 values(2);" ./psql -d postgres -c "INSERT into t1 values(3);" ./psql -d postgres -c "INSERT into t1 values(4);" ./pg_basebackup -h localhost -X stream -v -W -R -D ../standby/ # postgresql.conf file in new location mkdir ../new_path cat << EOF >> ../new_path/postgresql.conf max_replication_slots = 1 port = 9000 EOF # postgresql.conf file in default location cat << EOF >> ../standby/postgresql.conf max_replication_slots = 0 port = 9000 EOF ./pg_ctl -D ../standby -l standby.log start -o "-c config_file=../new_path/postgresql.conf" ./pg_createsubscriber -D ../standby -S 'host=localhost port=9000 dbname=postgres' -P 'host=localhost port=5432 dbname=postgres' -d postgres -r
