Last updated April 15, 2025

Migrating Applications from Cedar Private Spaces to Fir Private Spaces

This guide helps you migrate your applications from Heroku Private Spaces running on the Cedar generation to the new Fir generation with minimal downtime.

You can’t directly transfer an app between these different generations. Due to significant architectural differences, particularly the adoption of Cloud Native Buildpacks (CNB), ARM-based infrastructure, and IPv6 defaults in Fir, you must manually migrate your apps.

See the Heroku Generations article to reference all applicable differences between the Cedar and Fir generations.

Before the Migration

Configure a Custom Maintenance Page

Configure a custom page on your existing Cedar space app to show users during maintenance mode while your app migrates.

Plan For Downtime

Reduce the TTL values for your DNS entries to 1 minute (60 seconds) a few days before the migration to minimize downtime. The migration process includes updating your DNS entries to point to the new app running in the Fir space. Plan for some downtime to allow for DNS updates to propagate.

Migrating data to Private-tier data services within the Fir Space also requires a period of downtime.

Review Application Compatibility with Fir

Before migrating, assess your application’s compatibility with the Fir platform’s key characteristics:

• Cloud Native Buildpacks (CNB): Fir exclusively uses CNB. Applications using Classic Cedar buildpacks must be migrated to use CNB. Review how to set your Cloud Native Buildpack and adapt your build process.

• Graviton (ARM) Architecture: Fir dynos currently run on ARM-based Graviton processors. Ensure your application code and all dependencies are compatible with ARM architecture. x86-specific binaries or dependencies may result in build errors during deployment on the Fir Generation.

• Default IPv6 Networking: Fir Spaces default to IPv6 networking. Verify your application and any connected services can correctly bind to and operate over IPv6.

Review Add-ons Availability and Requirements

You must reprovision your add-ons on your new Fir application. Add-on availability and integration may differ in Fir spaces. You can verify that any add-on is compatible with Fir by filtering for Fir Gen Apps in the Heroku Elements marketplace or checking the “Supported Generations” section on each individual add-on’s Elements page.

While third-party OTel-native observability platforms can work out of the box, tooling that relies on syslog format is not yet be compatible with Fir.

The Migration Process

The following steps describe the typical migration process from a Cedar space to a Fir space.

1. Create a new Fir space from the dashboard or use the --generation fir flag with the heroku spaces:create CLI command to specify the Fir generation.
2. Create a new Heroku app from the dashboard or CLI within the new space.
3. Adapt and deploy your code: Update your application deployment process to use Cloud Native Buildpacks (CNB) compatible with the Fir platform. Test the build process thoroughly. Deploy your CNB-compatible code to your new app. Ensure compatibility with ARM architecture.
4. Provision your add-ons compatible with the Fir and scale your dynos. If you used a deployment method that automatically configured resources, verify the provisioned add-ons and dyno formations are correct for Fir.
5. Migrate Heroku Data services (recommended): While an app in a Fir space can connect to data services outside the space, such as services still in the Cedar environment, migrating them to the Fir space provides network isolation and security benefits.
   • Heroku Postgres: To minimize downtime, use the follower changeover method. This method allows your existing database to continue operating while the new private database provisions. You must reassign dataclips associated with the old database to the new one. To recover these dataclips, open a support ticket via help.heroku.com.
   • Heroku Key-Value Store: Use the fork method to migrate while your app is in maintenance mode.
   • Heroku Kafka: Follow these instructions to migrate while in maintenance mode.
6. Configure Custom Domains and SSL: Certain apps may allow the same domain to be temporarily assigned to both your existing Cedar space and new Fir space apps to reduce downtime. Contact Heroku Support to request this “domain forcing” for your new Fir app. If they confirm it isn’t possible, remove the custom domains from your Cedar app and add them to the new Fir app during your maintenance window.
7. Update DNS: Update your DNS entries to point to the new space app’s endpoint(s). After confirming propagation, restore your DNS TTL values to normal.
8. Monitor your new Fir app. Monitor logs for errors and check metrics for performance.