Use Flipper 0.21.0

This allows us to remove a custom patch that has now been accepted
upstream.

Gemfile

@@ -488,9 +488,9 @@ gem 'google-protobuf', '~> 3.15.8'
 gem 'toml-rb', '~> 1.0.0'
 
 # Feature toggles
-gem 'flipper', '~> 0.17.1'
-gem 'flipper-active_record', '~> 0.17.1'
-gem 'flipper-active_support_cache_store', '~> 0.17.1'
+gem 'flipper', '~> 0.21.0'
+gem 'flipper-active_record', '~> 0.21.0'
+gem 'flipper-active_support_cache_store', '~> 0.21.0'
 gem 'unleash', '~> 0.1.5'
 gem 'gitlab-experiment', '~> 0.5.4'
 

Gemfile.lock

@@ -372,13 +372,13 @@ GEM
       rake
     ffi-yajl (2.3.4)
       libyajl2 (~> 1.2)
-    flipper (0.17.1)
-    flipper-active_record (0.17.1)
-      activerecord (>= 4.2, < 7)
-      flipper (~> 0.17.1)
-    flipper-active_support_cache_store (0.17.1)
-      activesupport (>= 4.2, < 7)
-      flipper (~> 0.17.1)
+    flipper (0.21.0)
+    flipper-active_record (0.21.0)
+      activerecord (>= 5.0, < 7)
+      flipper (~> 0.21.0)
+    flipper-active_support_cache_store (0.21.0)
+      activesupport (>= 5.0, < 7)
+      flipper (~> 0.21.0)
     flowdock (0.7.1)
       httparty (~> 0.7)
       multi_json
@@ -1454,9 +1454,9 @@ DEPENDENCIES
   faraday_middleware-aws-sigv4 (~> 0.3.0)
   fast_blank
   ffaker (~> 2.10)
-  flipper (~> 0.17.1)
-  flipper-active_record (~> 0.17.1)
-  flipper-active_support_cache_store (~> 0.17.1)
+  flipper (~> 0.21.0)
+  flipper-active_record (~> 0.21.0)
+  flipper-active_support_cache_store (~> 0.21.0)
   flowdock (~> 0.7)
   fog-aliyun (~> 0.3)
   fog-aws (~> 3.9)

config/initializers/flipper.rb

+# frozen_string_literal: true
+
+Rails.application.configure do
+  config.flipper.preload = false
+  config.flipper.memoizer = false
+end

lib/feature.rb

@@ -18,6 +18,10 @@ class Feature
     superclass.table_name = 'feature_gates'
   end
 
+  # To enable EE overrides
+  class ActiveSupportCacheStoreAdapter < Flipper::Adapters::ActiveSupportCacheStore
+  end
+
   InvalidFeatureFlagError = Class.new(Exception) # rubocop:disable Lint/InheritException
 
   class << self
@@ -167,7 +171,8 @@ class Feature
         ActiveSupportCacheStoreAdapter.new(
           active_record_adapter,
           l2_cache_backend,
-          expires_in: 1.hour)
+          expires_in: 1.hour,
+          write_through: true)
 
       # Thread-local L1 cache: use a short timeout since we don't have a
       # way to expire this cache all at once

lib/feature/active_support_cache_store_adapter.rb

-# frozen_string_literal: true
-
-# rubocop:disable Gitlab/NamespacedClass
-# This class was already nested this way before moving to a separate file
-class Feature
-  class ActiveSupportCacheStoreAdapter < Flipper::Adapters::ActiveSupportCacheStore
-    # This patch represents https://github.com/jnunemaker/flipper/pull/512. In
-    # Flipper 0.21.0 and later, we can remove this and just pass `write_through:
-    # true` to the constructor in `Feature.build_flipper_instance`.
-
-    extend ::Gitlab::Utils::Override
-
-    override :enable
-    def enable(feature, gate, thing)
-      result = @adapter.enable(feature, gate, thing)
-      @cache.write(key_for(feature.key), @adapter.get(feature), @write_options)
-      result
-    end
-
-    override :disable
-    def disable(feature, gate, thing)
-      result = @adapter.disable(feature, gate, thing)
-      @cache.write(key_for(feature.key), @adapter.get(feature), @write_options)
-      result
-    end
-
-    override :remove
-    def remove(feature)
-      result = @adapter.remove(feature)
-      @cache.delete(FeaturesKey)
-      @cache.write(key_for(feature.key), {}, @write_options)
-      result
-    end
-  end
-end
-# rubocop:disable Gitlab/NamespacedClass