Update gitlab-exporter to handle both namespace and non-namespaced Sidekiq keys
gitlab-exporter uses a namespaced Sidekiq.redis (https://gitlab.com/gitlab-org/gitlab-exporter/-/blob/master/lib/gitlab_exporter/sidekiq.rb#L196). We need gitlab-exporter to read both namespaced and non-namespace sidekiq keys for a smooth cutover.
For SaaS, we will need to update
- gitlab-exporter (add non-namespace support)
- gitlab-monitor cookbook (https://gitlab.com/gitlab-cookbooks/gitlab-monitor/-/blob/master/attributes/default.rb)
- chef-repo to add in the envvar/feature flag (https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/blob/master/roles/gprd-base-db-redis-server-sidekiq.json#L23)
Post namespace deprecation
- update gitlab-exporter to not require namespace
- update gitlab-monitor cookbook with new version of exporter
- update chef to deploy new version of exporter
Note: omnibus-gitlab needs to be updated too since gitlab-exporter is shipped in omnibus distributions. But still unsure if we need to release the version of gitlab-exporter that handles both namespaces and non-namespaced keys if self-managed users will do a cut-over via post-deployment migration on a version upgrade. We could note that there will be a short window where Sidekiq metrics are disrupted (new metric exporter would detect no metrics but they would start showing on rollout, and show accurately after the post-deployment migration).