Detecting5xxForRegistry is flappy
sum(backend_code:haproxy_server_http_responses_total:irate1m{backend="registry",code="5xx",tier="lb"}) >0
is really flappy in the presence of sporadic errors, I believe mainly because of irate1m, irate being 'the last two samples', and over only 1m. I think we need to re-evaluate what this is doing; I'm thinking a new synthetic 'rate5m' might be more useful to smooth it out, so we get better stronger more consistent signal when things are going wrong. It probably needs a small number other than 0, but that's TBD; with a smoother signal, >0 may be sufficient.
/cc @cmcfarland