Placeholder issue, spun out of https://gitlab.com/gitlab-com/gl-infra/scalability/-/issues/865 The workloads and characteristics of queries hitting our primary DB and our secondary DBs are very different. As such we should monitor them independently. At present, they are lumped together in `gitlab_sql_duration_seconds_bucket`. Worse, this score does not exclude Sidekiq, which drives a major portion of our primary traffic. See also https://gitlab.com/gitlab-com/gl-infra/scalability/-/issues/873, which is this issue, for logs. ### Solution Solution is discussed at at https://gitlab.com/gitlab-com/gl-infra/scalability/-/issues/873#note_511091812. - Broadcast an instrumentation events after redirection: + [`Gitlab::Database::LoadBalancing::ConnectionProxy#read_using_load_balancer`](https://gitlab.com/gitlab-org/gitlab/-/blob/e1c3fb41dfa09f2f42dd749e3093548f2648b368/ee/lib/gitlab/database/load_balancing/connection_proxy.rb#L68) broadcast replica events + [`Gitlab::Database::LoadBalancing::ConnectionProxy#write_using_load_balancer`](https://gitlab.com/gitlab-org/gitlab/-/blob/e1c3fb41dfa09f2f42dd749e3093548f2648b368/ee/lib/gitlab/database/load_balancing/connection_proxy.rb#L81) broadcast primary events + The ones in method missing broadcast primary events - Dispatch prometheus metrics