docs: function calWeight(infos) {
      debug('开始计算calWeight');
      infos = infos.map(function (item) {
          if (item.weight === 0) {
              // 这是请求失败的
              return {value: item.host, weight: 0};
          }
          var runtimeLoadValue = runtimeLoad(item);
          var runtimeWeightValue = runtimeWeight(runtimeLoadValue);
          debug('runtimeWeight计算完毕：', runtimeWeightValue);
          var physicalWeightValue = physicalWeight(item);
          var finalWeightValue = finalWeight(runtimeWeightValue, physicalWeightValue);
          return {value: item.host, weight: finalWeightValue};
      });
      debug('calWeight执行完成了', infos);
      return infos;
  }