code: function wrapCountingMethod(method) {
    DruidNode.prototype[method] = function() {
      var self = this
        , args = utils.args(arguments, 0)
        , callback = args.pop()
  
      self.active++
  
      debug('Active calls to Druid node ' + this.data.id + ': ' + this.active)
  
      function wrapper() {
        self.active--
  
        callback.apply(null, arguments)
      }
  
      args.push(wrapper)
  
      Client.prototype[method].apply(this, args)
    }
  }
docs: Wrap {@link Client} methods to count number of concurrent running queries