Hello,
I have a cluster with a streaming replication primary, and two hot standbys (PostgreSQL 12.8). Today I connected to one of the standbys, and accidentally executed a CREATE TABLE statement. To my surprise, it created the table, and the change was visible on the primary and also on both standbys. I examined this behaviour, and found the following. If I connect to the standby using psql cli then the database is read-only, as expected:
test=> create table test(id int8 not null primary key);
ERROR: cannot execute CREATE TABLE in a read-only transaction
But if I connect to the standby using dbeaver, then somehow the database becomes writable. Dbeaver runs on my computer, the standby runs on a separate network and the connection is established through an ssh tunnel. The primary instance is located inside another network (actually in a different datacenter), and it is behind a VPN. In other words, it is technically impossible for dbeaver to connect to the primary. And yet somehow it can make changes in the database.
Am I missing something? Is there a possibility that the hot standby forwards SQL statements to the primary? I was not aware of such functionality.
Right now, it imposes a security risk in our environment, so I would really like to know how this works.
Thanks,
Laszlo