def connection
        overlord = zk.registry["#{config.discovery_path}/druid:overlord"].first
        raise DruidDB::ConnectionError, 'no druid overlords available' if overlord.nil?
        zk.registry["#{config.discovery_path}/druid:overlord"].rotate! # round-robin load balancing
        DruidDB::Connection.new(host: overlord[:host], port: overlord[:port])