Fedora mirrors tend to drop RPMs very quickly. As we don't want to be constantly chasing every single tiny update, we have decided to set up our own mirror on GCS.
The mirror only contains RPMs that the sandboxroot actually uses, and is managed by running the mirror tool from this directory.
The mirror is enabled by default whenever you use Bazel (see repositories.bzl in this directory).
Any time you run third_party/sandboxroot/regenerate.sh, the last step calls mirror sync. If that fails for some reason (eg. you were not logged into GCS), you can run it manually:
$ bazel run :mirror sync
If you want to just check whether everything's properly synced, you can run:
$ bazel run :mirror check
To do a full scan (downloading and checking SHA256 sums) do:
$ bazel run :mirror check --deep