code: function(error) {
          if (error) {
            log.error(t.logId + 'probeDisconnect', error);
            return callback(error);
          }
          var duration = logCtxt.duration = Date.now() - probe.connectTime;
          probe.off('change', monitorProxy.probeChange);
          monitorProxy.probe = monitorProxy.probeChange = null;
          delete t.incomingMonitorsById[probeId];
          log.info(t.logId + 'probeDisconnected', logCtxt);
          stat.time(t.logId + 'probeDisconnected', duration);
          return callback(null);
        }
docs: Called upon disconnect (internal or external)