Merge branch 'sh-feature-flag-persisted-process-cache' into 'master'

Move feature flag list into process cache

See merge request gitlab-org/gitlab!27511

changelogs/unreleased/sh-feature-flag-persisted-process-cache.yml

+---
+title: Move feature flag list into process cache
+merge_request: 27511
+author:
+type: performance

lib/feature.rb

@@ -38,7 +38,7 @@ class Feature
         begin
           # We saw on GitLab.com, this database request was called 2300
           # times/s. Let's cache it for a minute to avoid that load.
-          Gitlab::ThreadMemoryCache.cache_backend.fetch('flipper:persisted_names', expires_in: 1.minute) do
+          Gitlab::ProcessMemoryCache.cache_backend.fetch('flipper:persisted_names', expires_in: 1.minute) do
             FlipperFeature.feature_names
           end
         end

spec/lib/feature_spec.rb

@@ -42,7 +42,7 @@ describe Feature do
         .once
         .and_call_original
 
-      expect(Gitlab::ThreadMemoryCache.cache_backend)
+      expect(Gitlab::ProcessMemoryCache.cache_backend)
         .to receive(:fetch)
         .once
         .with('flipper:persisted_names', expires_in: 1.minute)