1 files changed, 72 insertions, 0 deletions
diff --git a/lib/gitlab/container_repository/tags/cache.rb b/lib/gitlab/container_repository/tags/cache.rb
new file mode 100644
index 00000000000..ff457fb9219
--- /dev/null
+++ b/lib/gitlab/container_repository/tags/cache.rb
@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module ContainerRepository
+    module Tags
+      class Cache
+        def initialize(container_repository)
+          @container_repository = container_repository
+          @cached_tag_names = Set.new
+        end
+
+        def populate(tags)
+          return if tags.empty?
+
+          # This will load all tags in one Redis roundtrip
+          # the maximum number of tags is configurable and is set to 200 by default.
+          # https://gitlab.com/gitlab-org/gitlab/blob/master/doc/user/packages/container_registry/index.md#set-cleanup-limits-to-conserve-resources
+          keys = tags.map(&method(:cache_key))
+          cached_tags_count = 0
+
+          ::Gitlab::Redis::Cache.with do |redis|
+            tags.zip(redis.mget(keys)).each do |tag, created_at|
+              next unless created_at
+
+              tag.created_at = DateTime.rfc3339(created_at)
+              @cached_tag_names << tag.name
+              cached_tags_count += 1
+            end
+          end
+
+          cached_tags_count
+        end
+
+        def insert(tags, max_ttl_in_seconds)
+          return unless max_ttl_in_seconds
+          return if tags.empty?
+
+          # tags with nil created_at are not cacheable
+          # tags already cached don't need to be cached again
+          cacheable_tags = tags.select do |tag|
+            tag.created_at.present? && !tag.name.in?(@cached_tag_names)
+          end
+
+          return if cacheable_tags.empty?
+
+          now = Time.zone.now
+
+          ::Gitlab::Redis::Cache.with do |redis|
+            # we use a pipeline instead of a MSET because each tag has
+            # a specific ttl
+            redis.pipelined do
+              cacheable_tags.each do |tag|
+                created_at = tag.created_at
+                # ttl is the max_ttl_in_seconds reduced by the number
+                # of seconds that the tag has already existed
+                ttl = max_ttl_in_seconds - (now - created_at).seconds
+                ttl = ttl.to_i
+                redis.set(cache_key(tag), created_at.rfc3339, ex: ttl) if ttl > 0
+              end
+            end
+          end
+        end
+
+        private
+
+        def cache_key(tag)
+          "container_repository:{#{@container_repository.id}}:tag:#{tag.name}:created_at"
+        end
+      end
+    end
+  end
+end