text: 
  module.exports = function (pmx, tracer) {
    var latency;
    var throughput;
  
    tracer.on('mongo', function (data) {
      if (!latency) {
        latency = pmx.probe().histogram({
          name: 'Mongo: Response time',
          type: 'mongodb/latency',
          measurement: 'mean',
          unit: 'ms'
        });
      }
      if (!throughput) {
        throughput = pmx.probe().meter({
          name: 'Mongo: Throughput',
          samples: 60,
          type: 'mongodb/throughput',
          unit: 'req/min'
        });
      }
  
      data = JSON.parse(data);
      throughput.mark();
      if (data.duration) {
        latency.update(data.duration);
      }
    });
  };
  