Merge branch 'actioncable-gcp-memorystore' into 'master'

Support Action Cable on GCP Memorystore

See merge request gitlab-org/gitlab!75173

config/initializers/action_cable.rb

@@ -9,6 +9,8 @@ Rails.application.configure do
   config.action_cable.worker_pool_size = Gitlab::ActionCable::Config.worker_pool_size
 end
 
+ActionCable::SubscriptionAdapter::Base.prepend(Gitlab::Patch::ActionCableSubscriptionAdapterIdentifier)
+
 # https://github.com/rails/rails/blob/bb5ac1623e8de08c1b7b62b1368758f0d3bb6379/actioncable/lib/action_cable/subscription_adapter/redis.rb#L18
 ActionCable::SubscriptionAdapter::Redis.redis_connector = lambda do |config|
   args = config.except(:adapter, :channel_prefix)

lib/gitlab/patch/action_cable_subscription_adapter_identifier.rb

+# frozen_string_literal: true
+
+# Modifies https://github.com/rails/rails/blob/v6.1.4.1/actioncable/lib/action_cable/subscription_adapter/base.rb so
+# that we do not overwrite an id that was explicitly set to `nil` in cable.yml.
+# This is needed to support GCP Memorystore. See https://github.com/rails/rails/issues/38244.
+
+module Gitlab
+  module Patch
+    module ActionCableSubscriptionAdapterIdentifier
+      def identifier
+        @server.config.cable.has_key?(:id) ? @server.config.cable[:id] : super # rubocop:disable Gitlab/ModuleWithInstanceVariables
+      end
+    end
+  end
+end

spec/initializers/action_cable_subscription_adapter_identifier_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'ActionCableSubscriptionAdapterIdentifier override' do
+  describe '#identifier' do
+    context 'when id key is nil on cable.yml' do
+      it 'does not override server config id with action cable pid' do
+        config = {
+          adapter: 'redis',
+          url: 'unix:/home/localuser/redis/redis.socket',
+          channel_prefix: 'test_',
+          id: nil
+        }
+        ::ActionCable::Server::Base.config.cable = config
+
+        sub = ActionCable.server.pubsub.send(:redis_connection)
+
+        expect(sub.connection[:id]).to eq('redis:///home/localuser/redis/redis.socket/0')
+        expect(ActionCable.server.config.cable[:id]).to be_nil
+      end
+    end
+  end
+end