docs: public static void collectStats(final StatsCollector collector) {
      collector.record("connectionmgr.connections", channels.size(), "type=open");
      collector.record("connectionmgr.connections", connections_rejected,
          "type=rejected");
      collector.record("connectionmgr.connections", connections_established, 
          "type=total");
      collector.record("connectionmgr.exceptions", exceptions_closed, 
          "type=closed");
      collector.record("connectionmgr.exceptions", exceptions_reset, 
          "type=reset");
      collector.record("connectionmgr.exceptions", exceptions_timeout, 
          "type=timeout");
      collector.record("connectionmgr.exceptions", exceptions_unknown, 
          "type=unknown");
    }