Use Rails.cache instead of Redis directly

Signed-off-by: Rémy Coutable <remy@rymai.me>

lib/gitlab/performance_bar.rb

@@ -3,7 +3,7 @@ module Gitlab
     ALLOWED_USER_IDS_KEY = 'performance_bar_allowed_user_ids'.freeze
     # The time (in seconds) after which a set of allowed user IDs is expired
     # automatically.
-    ALLOWED_USER_IDS_TIME_TO_LIVE = 10.minutes.to_i
+    ALLOWED_USER_IDS_TIME_TO_LIVE = 10.minutes
 
     def self.enabled?(current_user = nil)
       Feature.enabled?(:gitlab_performance_bar, current_user)
@@ -20,28 +20,13 @@ module Gitlab
     end
 
     def self.allowed_user_ids
-      Gitlab::Redis.with do |redis|
-        if redis.exists(cache_key)
-          redis.smembers(cache_key).map(&:to_i)
+      Rails.cache.fetch(cache_key, expires_in: ALLOWED_USER_IDS_TIME_TO_LIVE) do
+        group = Group.find_by_full_path(allowed_group_name)
+
+        if group
+          GroupMembersFinder.new(group).execute.pluck(:user_id)
         else
-          group = Group.find_by_full_path(allowed_group_name)
-          # Redis#sadd doesn't accept an empty array, but we still want to use
-          # Redis to let us know that no users are allowed, so we set the
-          # array to [-1] in this case.
-          user_ids =
-            if group
-              GroupMembersFinder.new(group).execute
-                .pluck(:user_id).presence || [-1]
-            else
-              [-1]
-            end
-
-          redis.multi do
-            redis.sadd(cache_key, user_ids)
-            redis.expire(cache_key, ALLOWED_USER_IDS_TIME_TO_LIVE)
-          end
-
-          user_ids
+          []
         end
       end
     end

spec/lib/gitlab/performance_bar_spec.rb

@@ -31,19 +31,11 @@ describe Gitlab::PerformanceBar do
       described_class.allowed_user?(user)
     end
 
-    it 'caches the allowed user IDs in Redis', :redis do
+    it 'caches the allowed user IDs in cache', :caching do
       expect do
         expect(described_class.allowed_user?(user)).to be_truthy
       end.not_to exceed_query_limit(0)
     end
-
-    it 'caches the allowed user IDs for 10 minutes', :redis do
-      ttl_cached_user_ids = Gitlab::Redis.with do |redis|
-        redis.ttl(described_class.cache_key)
-      end
-
-      expect(ttl_cached_user_ids).to be <= 10.minutes
-    end
   end
 
   describe '.allowed_user?' do