I need to create a replica of existing database, that would copy any changing operation from master to slave, I.e create a mirror some sort of. I found a lot of examples in web but they all describes process when master and slave are on different servers. I would like to create a write replica on the same server where master is located , without spinning up second instance of Postgres.
Is it possible to do so and could you point me a direction where I could find a solution how to do it?
Thank you.
P.S. I understand that replication on 2 servers is better, but I just need to do it on one common server.
If you want physical replication, you will need to run two instances of PostgreSQL. If they are on the same server machine, they will need to have different port numbers. The different port numbers is the only complexity, otherwise it is just like running on two different servers.
If you want logical replication, you can do that within a single instance, but you will need to jump through some hoops to create the subscription intra-instance, as described in the "Notes" section
You could consider using a simple trigger to insert/update/delete data on the other database as soon as the main one get modified.
A more "professional" way would be to use synchronous replication.