Heroku customers who would like to transition across a public-private network boundary (either from a public space to a private space, or from a private space to a public space) have limited options for doing so. The boundary represents a firewall that is designed to prevent access from the public space to the private space. Within the private space itself, there are security protocols in place to prevent the exfiltration of data. Migrations across the boundary are difficult by design; this difficulty is an artifact of the additional layer of security granted by private spaces.
The preferred method for migrating a cluster is to use a blue-green deployment strategy. There are several general steps to this approach:
This strategy will accommodate migrations across the boundary, regardless of whether you're going from public to private, or private to public.
If a blue-green deployment strategy is not possible for some reason, please contact us to set up a call. We will consider alternatives based on your specific needs.