PostgreSQL has replication built in now. I set it up at work, and it replicates reliably, in a fraction of a second. I've never had to fail over, but it seems straightforward to do so. The only hard part was following Postgres's documentation in setting it all up. It seemed to me a bit scattered to me. I had to jump around to different sections before I put it all together in my mind.
What do you use? Are there some instructions/articles that you'd recommend reading? Is it anything like Galera?
I know of BDR, but there hasn't much news about it lately, especially with more recent versions of Pg.
We like Galera for our simple needs: we use keepalived to do health checks, and if they pass the node participates in the VRRP cluster. If one node goes down/bad, another takes over.
If you want multi master in Postgres, I think BDR is going to be your best option, but the version for PG 10+ isn't open source so you'll have to pay for it. We're using the open source version on PG 9.4 currently in production, it's worked fine so far.
