1 files changed, 62 insertions, 3 deletions

diff --git a/lib/api/helpers/caching.rb b/lib/api/helpers/caching.rb
index d0f22109879..f24ac7302c1 100644
--- a/lib/api/helpers/caching.rb
+++ b/lib/api/helpers/caching.rb
@@ -11,6 +11,11 @@ module API
       # @return [ActiveSupport::Duration]
       DEFAULT_EXPIRY = 1.day
 
+      # @return [Hash]
+      DEFAULT_CACHE_OPTIONS = {
+        race_condition_ttl: 5.seconds
+      }.freeze
+
       # @return [ActiveSupport::Cache::Store]
       def cache
         Rails.cache
@@ -40,7 +45,7 @@ module API
       # @param expires_in [ActiveSupport::Duration, Integer] an expiry time for the cache entry
       # @param presenter_args [Hash] keyword arguments to be passed to the entity
       # @return [Gitlab::Json::PrecompiledJson]
-      def present_cached(obj_or_collection, with:, cache_context: -> (_) { current_user.cache_key }, expires_in: DEFAULT_EXPIRY, **presenter_args)
+      def present_cached(obj_or_collection, with:, cache_context: -> (_) { current_user&.cache_key }, expires_in: DEFAULT_EXPIRY, **presenter_args)
         json =
           if obj_or_collection.is_a?(Enumerable)
             cached_collection(
@@ -63,8 +68,59 @@ module API
         body Gitlab::Json::PrecompiledJson.new(json)
       end
 
+      # Action caching implementation
+      #
+      # This allows you to wrap an entire API endpoint call in a cache, useful
+      # for short TTL caches to effectively rate-limit an endpoint. The block
+      # will be converted to JSON and cached, and returns a
+      # `Gitlab::Json::PrecompiledJson` object which will be exported without
+      # secondary conversion.
+      #
+      # @param key [Object] any object that can be converted into a cache key
+      # @param expires_in [ActiveSupport::Duration, Integer] an expiry time for the cache entry
+      # @return [Gitlab::Json::PrecompiledJson]
+      def cache_action(key, **cache_opts)
+        json = cache.fetch(key, **apply_default_cache_options(cache_opts)) do
+          response = yield
+
+          if response.is_a?(Gitlab::Json::PrecompiledJson)
+            response.to_s
+          else
+            Gitlab::Json.dump(response.as_json)
+          end
+        end
+
+        body Gitlab::Json::PrecompiledJson.new(json)
+      end
+
+      # Conditionally cache an action
+      #
+      # Perform a `cache_action` only if the conditional passes
+      def cache_action_if(conditional, *opts, **kwargs)
+        if conditional
+          cache_action(*opts, **kwargs) do
+            yield
+          end
+        else
+          yield
+        end
+      end
+
+      # Conditionally cache an action
+      #
+      # Perform a `cache_action` unless the conditional passes
+      def cache_action_unless(conditional, *opts, **kwargs)
+        cache_action_if(!conditional, *opts, **kwargs) do
+          yield
+        end
+      end
+
       private
 
+      def apply_default_cache_options(opts = {})
+        DEFAULT_CACHE_OPTIONS.merge(opts)
+      end
+
       # Optionally uses a `Proc` to add context to a cache key
       #
       # @param object [Object] must respond to #cache_key
@@ -119,8 +175,11 @@ module API
         objs.flatten!
         map = multi_key_map(objs, context: context)
 
-        cache.fetch_multi(*map.keys, **kwargs) do |key|
-          yield map[key]
+        # TODO: `contextual_cache_key` should be constructed based on the guideline https://docs.gitlab.com/ee/development/redis.html#multi-key-commands.
+        Gitlab::Instrumentation::RedisClusterValidator.allow_cross_slot_commands do
+          cache.fetch_multi(*map.keys, **kwargs) do |key|
+            yield map[key]
+          end
         end
       end