Migrate Free tier images

Context

This is part of the work to upgrade and migrate the GitLab.com container registry to a new version backed by a metadata database and online garbage collection (&5523 (closed)). This will be achieved following the gradual migration plan detailed in container-registry#374 (closed).

Task

Perform the Phase 2 (existing container repositories) general percentage-based rollout for Free tier namespace images.

Monitoring and Known Issues

These are the known issues to date and the json.error message pattern that will appear in the logs for each:

• Cloud Storage hiccups. Nothing to do, the import is retried automatically - Very rare

  pre importing tagged manifests: pre importing manifest: pre importing manifest: transferring blob with digest sha256:XXX: failed to transfer blob digest="sha256:XXX" cleanup=true cleanupError="gcs: context canceled": "partial transfer from <gcs_path_1> to <gcs_path_2>: copying data from source to destination: context canceled"

If you're monitoring the migration, use this log view to identify import failures.

If you notice any imports failing with a json.error that does not match one of the above, please disable the main feature flag (container_registry_migration_phase2_enabled) immediately and report the error here for investigation.