Just dropping a note for people who have deployed their own Hydra. This is advanced notice on an upcoming migration to Hydra’s schema. Almost all migrations to Hydra’s database are fast and performed automatically by
hydra-init when starting the server. However, this migration will potentially take many hours and possibly over a day for large deployments. Because of that, we have designed the migration as a two-phased deployment, with a command-line program which will run the slowest part of the migration while the server is running.
This means, however, that Hydra admins must take care in the deployment and will ideally do the deploy in two phases.
Some information about the problem and what we’re doing: https://github.com/NixOS/hydra/pull/710 if you have any feedback on how this is being done or ways to make it easier on Hydra admins, please do comment.