Using Heroku Postgres From A Fly App

Summary

A Fly application can use Heroku Postgres without migrating the application itself, with Heroku hosting an add-on-only app that provides the database. The setup provisions a Hobby Dev Heroku Postgres database, retrieves its URI credentials, and passes DATABASE_URL to the Fly deployment as a secret. A Node REST API using Sequelize parses that URI with pg-connection-string, then supplies the database, user, password, and host while enabling SSL and setting rejectUnauthorized to false for Heroku’s certificate-chain issue. After fly deploy, the app connects externally to Postgres, but the Hobby plan limits it to 20 connections unless upgraded. The article presents Heroku’s US and Europe data-center choices as a way to keep the database relatively close while Fly places the application near users, and warns that credentials rotate periodically without notification.

Takeaways

1. 1

   Heroku’s Hobby Dev Postgres plan provides a 1GB database capable of holding up to 10,000 rows in the example.

2. 2

   External access to Heroku Postgres requires SSL; the Sequelize configuration also disables rejection of self-signed certificates in Heroku’s server certificate chain.

3. 3

   Heroku rotates database credentials periodically and does not warn applications when they change; the database is also limited to 20 connections unless the plan is upgraded.