1 files changed, 103 insertions, 0 deletions
diff --git a/lib/gitlab/gitaly_client/with_feature_flag_actors.rb b/lib/gitlab/gitaly_client/with_feature_flag_actors.rb
new file mode 100644
index 00000000000..92fc524b724
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+++ b/lib/gitlab/gitaly_client/with_feature_flag_actors.rb
@@ -0,0 +1,103 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module GitalyClient
+    # This module is responsible for collecting feature flag actors in Gitaly Client. Unlike normal feature flags used
+    # in Gitlab development, feature flags passed to Gitaly are pre-evaluated at Rails side before being passed to
+    # Gitaly. As a result, we need to collect all possible actors for the evaluation before issue any RPC. At this
+    # layer, the only parameter we have is raw repository. We need to infer other actors from the repository. Adding
+    # extra SQL queries before any RPC are not good for the performance. We applied some quirky optimizations here to
+    # avoid issuing SQL queries. However, in some less common code paths, a couple of queries are expected.
+    module WithFeatureFlagActors
+      include Gitlab::Utils::StrongMemoize
+
+      attr_accessor :repository_actor
+
+      # gitaly_client_call performs Gitaly calls including collected feature flag actors. The actors are retrieved
+      # from repository actor and memoized. The service must set `self.repository_actor = a_repository` beforehand.
+      def gitaly_client_call(*args, **kargs)
+        return GitalyClient.call(*args, **kargs) unless actors_aware_gitaly_calls?
+
+        unless repository_actor
+          Gitlab::ErrorTracking.track_and_raise_for_dev_exception(
+            Feature::InvalidFeatureFlagError.new("gitaly_client_call called without setting repository_actor")
+          )
+        end
+
+        GitalyClient.with_feature_flag_actors(
+          repository: repository_actor,
+          user: user_actor,
+          project: project_actor,
+          group: group_actor
+        ) do
+          GitalyClient.call(*args, **kargs)
+        end
+      end
+
+      # gitaly_feature_flag_actors returns a hash of actors implied from input repository. If actors_aware_gitaly_calls
+      # flag is not on, this method returns an empty hash.
+      def gitaly_feature_flag_actors(repository)
+        return {} unless actors_aware_gitaly_calls?
+
+        container = find_repository_container(repository)
+        {
+          repository: repository,
+          user: Feature::Gitaly.user_actor,
+          project: Feature::Gitaly.project_actor(container),
+          group: Feature::Gitaly.group_actor(container)
+        }
+      end
+
+      # Use actor here means the user who originally perform the action. It is collected from ApplicationContext. As
+      # this information is widely propagated in all entry points, User actor should be available everywhere, even in
+      # background jobs.
+      def user_actor
+        strong_memoize(:user_actor) do
+          Feature::Gitaly.user_actor
+        end
+      end
+
+      # TODO: replace this project actor by Repo actor
+      def project_actor
+        strong_memoize(:project_actor) do
+          Feature::Gitaly.project_actor(repository_container)
+        end
+      end
+
+      def group_actor
+        strong_memoize(:group_actor) do
+          Feature::Gitaly.group_actor(repository_container)
+        end
+      end
+
+      private
+
+      def repository_container
+        strong_memoize(:repository_container) do
+          find_repository_container(repository_actor)
+        end
+      end
+
+      def find_repository_container(repository)
+        return if repository&.gl_repository.blank?
+
+        if repository.container.nil?
+          begin
+            identifier = Gitlab::GlRepository::Identifier.parse(repository.gl_repository)
+            identifier.container
+          rescue Gitlab::GlRepository::Identifier::InvalidIdentifier
+            nil
+          end
+        else
+          repository.container
+        end
+      end
+
+      def actors_aware_gitaly_calls?
+        Feature.enabled?(:actors_aware_gitaly_calls)
+      end
+    end
+  end
+end
+
+Gitlab::GitalyClient::WithFeatureFlagActors.prepend_mod_with('Gitlab::GitalyClient::WithFeatureFlagActors')