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Diffstat (limited to 'lib/gitlab/cache/helpers.rb')
-rw-r--r-- | lib/gitlab/cache/helpers.rb | 111 |
1 files changed, 111 insertions, 0 deletions
diff --git a/lib/gitlab/cache/helpers.rb b/lib/gitlab/cache/helpers.rb new file mode 100644 index 00000000000..7b11d6bc9ff --- /dev/null +++ b/lib/gitlab/cache/helpers.rb @@ -0,0 +1,111 @@ +# frozen_string_literal: true + +module Gitlab + module Cache + module Helpers + # @return [ActiveSupport::Duration] + DEFAULT_EXPIRY = 1.day + + # @return [ActiveSupport::Cache::Store] + def cache + Rails.cache + end + + def render_cached(obj_or_collection, with:, cache_context: -> (_) { current_user&.cache_key }, expires_in: Gitlab::Cache::Helpers::DEFAULT_EXPIRY, **presenter_args) + json = + if obj_or_collection.is_a?(Enumerable) + cached_collection( + obj_or_collection, + presenter: with, + presenter_args: presenter_args, + context: cache_context, + expires_in: expires_in + ) + else + cached_object( + obj_or_collection, + presenter: with, + presenter_args: presenter_args, + context: cache_context, + expires_in: expires_in + ) + end + + render Gitlab::Json::PrecompiledJson.new(json) + end + + private + + # Optionally uses a `Proc` to add context to a cache key + # + # @param object [Object] must respond to #cache_key + # @param context [Proc] a proc that will be called with the object as an argument, and which should return a + # string or array of strings to be combined into the cache key + # @return [String] + def contextual_cache_key(presenter, object, context) + return object.cache_key if context.nil? + + [presenter.class.name, object.cache_key, context.call(object)].flatten.join(":") + end + + # Used for fetching or rendering a single object + # + # @param object [Object] the object to render + # @param presenter [Grape::Entity] + # @param presenter_args [Hash] keyword arguments to be passed to the entity + # @param context [Proc] + # @param expires_in [ActiveSupport::Duration, Integer] an expiry time for the cache entry + # @return [String] + def cached_object(object, presenter:, presenter_args:, context:, expires_in:) + cache.fetch(contextual_cache_key(presenter, object, context), expires_in: expires_in) do + Gitlab::Json.dump(presenter.represent(object, **presenter_args).as_json) + end + end + + # Used for fetching or rendering multiple objects + # + # @param objects [Enumerable<Object>] the objects to render + # @param presenter [Grape::Entity] + # @param presenter_args [Hash] keyword arguments to be passed to the entity + # @param context [Proc] + # @param expires_in [ActiveSupport::Duration, Integer] an expiry time for the cache entry + # @return [Array<String>] + def cached_collection(collection, presenter:, presenter_args:, context:, expires_in:) + json = fetch_multi(presenter, collection, context: context, expires_in: expires_in) do |obj| + Gitlab::Json.dump(presenter.represent(obj, **presenter_args).as_json) + end + + json.values + end + + # An adapted version of ActiveSupport::Cache::Store#fetch_multi. + # + # The original method only provides the missing key to the block, + # not the missing object, so we have to create a map of cache keys + # to the objects to allow us to pass the object to the missing value + # block. + # + # The result is that this is functionally identical to `#fetch`. + def fetch_multi(presenter, *objs, context:, **kwargs) + objs.flatten! + map = multi_key_map(presenter, objs, context: context) + + # 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 + + # @param objects [Enumerable<Object>] objects which _must_ respond to `#cache_key` + # @param context [Proc] a proc that can be called to help generate each cache key + # @return [Hash] + def multi_key_map(presenter, objects, context:) + objects.index_by do |object| + contextual_cache_key(presenter, object, context) + end + end + end + end +end |