[Feature flag] Enable Unauthenticated Concurrency Limiter

What

Enable the :gitaly_limit_unauthenticated feature flag

Owners

• Team: Gitaly
• Most appropriate slack channel to reach out to: #g_gitaly
• Best individual to reach out to: @jcaigitlab, @qmnguyen0711

Expectations

What release does this feature occur in first?

%18.6

What are we expecting to happen?

When the feature flag is enabled and the new configuration for unauthenticated limits in the concurrency limiter is used, unauthenticated requests will be treated differently.

What might happen if this goes wrong?

Unauthenticated request do not get treated differently. But this is the default behavior.

What can we monitor to detect problems with this?

The Gitaly Overview dashboard's error charts

Roll Out Steps

• Enable on staging
  • Is the required code deployed on staging? (howto)
  • Enable on staging (howto)
  • Add featureflagstaging to this issue (howto)
  • Test on staging (howto)
  • Verify the feature flag was used by checking Prometheus metric gitaly_feature_flag_checks_total
• Enable on production
  • Is the required code deployed on production? (howto)
  • Progressively enable in production (howto)
  • Add featureflagproduction to this issue
  • Verify the feature flag was used by checking Prometheus metric gitaly_feature_flag_checks_total
• Create subsequent issues
  • To default enable the feature flag (optional, only required if backwards-compatibility concerns exist)
    • Create issue using the Feature Flag Default Enable template.
    • Set milestone to current+1 release
  • To Remove feature flag
    • Create issue using the Feature Flag Removal template.
    • Set milestone to current+1 (+2 if we created an issue to default enable the flag).

Please refer to the documentation of feature flags for further information.