Show canary / no-canary in the performance bar

@northrup mentioned in https://gitlab.com/gitlab-org/gitlab-ce/issues/52158#note_106576729 (and, previously, in https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/3680#note_59751403):

Back when we were talking about this I had asked for a descriptive text in the Performance Bar (that's only visible to GitLab staff) so that we could see which backend we were hitting. I still think we should do that.

We should do this.

@northrup: we currently show the first part of the hostname (my initial request here went to web-09-sv-gprd, for instance). Can we tell if we're on canary from another part of the hostname? What's the best and most robust method for us to detect this?

mentioned in issue #52158 (moved)

added gitlab.com label

added production request label

. Can we tell if we're on canary from another part of the hostname? What's the best and most robust method for us to detect this?

Every hostname that serves canary traffic will have -cny- in it, for example web-cny-01-sv-gprd. We also continue to set the CANARY ENV var for the canary hosts.

        "gitlab-rails": {
          "env": {
            "CANARY": "true"
         ...

@jarv that was fast, thanks! Which is more likely to hang around a long time:

• Canary hosts have -cny- in the hostname.
• Canary hosts have CANARY=true set.

?

I think it would be better to use the env var since who knows what we will do with host names in the future. This is what the application currently uses to set the favicon color.

@jarv great, I'm on it! I asked about removing the favicon in the other issue (I'm not sure why it was closed).

created branch 52421-show-canary-no-canary-in-the-performance-bar

mentioned in merge request !22222 (merged)

@smcgivern this is awesome! thank you!

closed via merge request !22222 (merged)

mentioned in commit 05dd7f97

added devopsplan label