1 files changed, 40 insertions, 0 deletions
diff --git a/lib/gitlab/patch/node_loader.rb b/lib/gitlab/patch/node_loader.rb
new file mode 100644
index 00000000000..79f4b17dd93
--- /dev/null
+++ b/lib/gitlab/patch/node_loader.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+# Patch to address https://gitlab.com/gitlab-com/gl-infra/scalability/-/issues/2212#note_1287996694
+# It uses hostname instead of IP address if the former is present in `CLUSTER NODES` output.
+if Gem::Version.new(Redis::VERSION) > Gem::Version.new('4.8.1')
+  raise 'New version of redis detected, please remove or update this patch'
+end
+
+module Gitlab
+  module Patch
+    module NodeLoader
+      def self.prepended(base)
+        base.class_eval do
+          # monkey-patches https://github.com/redis/redis-rb/blob/v4.8.0/lib/redis/cluster/node_loader.rb#L23
+          def self.fetch_node_info(node)
+            node.call(%i[cluster nodes]).split("\n").map(&:split).to_h do |arr|
+              [
+                extract_host_identifier(arr[1]),
+                (arr[2].split(',') & %w[master slave]).first # rubocop:disable Naming/InclusiveLanguage
+              ]
+            end
+          end
+
+          # Since `CLUSTER SLOT` uses the preferred endpoint determined by
+          # the `cluster-preferred-endpoint-type` config value, we will prefer hostname over IP address.
+          # See https://redis.io/commands/cluster-nodes/ for details on the output format.
+          #
+          # @param [String] Address info matching fhe format: <ip:port@cport[,hostname[,auxiliary_field=value]*]>
+          def self.extract_host_identifier(node_address)
+            ip_chunk, hostname, _auxiliaries = node_address.split(',')
+            return ip_chunk.split('@').first if hostname.blank?
+
+            port = ip_chunk.split('@').first.split(':')[1]
+            "#{hostname}:#{port}"
+          end
+        end
+      end
+    end
+  end
+end