in files/gitlab-cookbooks/package/libraries/config/roles/redis_master.rb [17:30]
def self.load_role
master_role = Gitlab['redis_master_role']['enable']
replica_role = Gitlab['redis_replica_role']['enable']
return unless master_role || replica_role
raise 'Cannot define both redis_master_role and redis_replica_role in the same machine.' if master_role && replica_role
Gitlab['gitlab_rails']['enable'] ||= false
Services.enable_group('redis_node') if master_role || replica_role
end