Heads up - this documentation on fly.io has some out of date information.
The Fly Postgres app is fully open source. Just fork fly-apps/postgres-ha and add whatever meets your needs. You can even update an existing cluster with your new image using
fly deploy --image. One caveat is that once you fork, you won’t be able to usefly postgrescommands to administer your app.
fly postgres commands do indeed work with forked images. And, that git repo should likely point to fly-apps/postgres-flex: Postgres HA setup using repmgr (github.com) instead of fly-apps/postgres-ha: Postgres + Stolon for HA clusters as Fly apps. (github.com). And I wonder if the postgres-ha repo should get a deprecation notice. I spent some unnecessary time following those instructions, not realizing there was a new image.