How We Built Fly Postgres

Summary

Fly.io describes how it built Fly Postgres as an automated database app rather than a managed database service. After initially resisting durable storage and database work, the company added attached disk storage and designed a deployable Postgres application with convenience commands, using Postgres streaming replication, Stolon, and Consul to support high availability. A two-node cluster can designate a writable leader and asynchronous standby, while Stolon’s sentinels, keepers, and proxies coordinate state, elect a replacement leader, and route connections; Consul introduces an additional failure mode. Backups use point-in-time, block-level snapshots of the volume, a platform capability that can also support other file-system databases. The post concludes that automated Postgres serves many apps, while managed database partnerships may suit users seeking a simpler experience.

Takeaways

1. 1

   Fly Postgres is an automated application customers deploy on Fly.io, not a fully managed database service.

2. 2

   Stolon’s sentinels, keepers, and proxies use Consul to coordinate leader election, replica management, and routing to the healthy leader.

3. 3

   Point-in-time snapshots of raw volume block devices provide Postgres restores and can generalize to other file-system-based databases.