Metric add, labels best practice

[imgalli]

Hi, we're using Open Telemetry JS to log various metrics to Prometheus. Whilst doing so we've seen a few different bits of documentation and API code that allows for this to be done in a few ways. My question is, what is the most performant way to do so.

counter.add(1, {
  pageType: 'post',
});

or

const pageTypePostBoundCounter = counter.bind({ pageType: 'post' });
pageTypePostBoundCounter.add(1);

// Record data using Instrument: It is recommended to keep a reference to the Bound Instrument instead of
// always calling `bind()` method for every operations.

https://github.com/open-telemetry/opentelemetry-js/blob/main/packages/opentelemetry-exporter-prometheus/README.md#usage

[dyladan]

The metrics implementation is still in its infancy. The bind method exists in order to make calls more performant, but it only yields performance benefits if the same bound counter is incremented many times. If you call c.add(1, labels), it first binds then does the increment. If you bind first, you are simply doing this bind step manually. The performance difference comes from the fact that if you call c.add(1, labels) 100 times it will bind 100 times. If you first bind then call boundC.add(1) 100 times you have still only bound one time.

const counter = meter.createCounter('counter');
const boundCounter = meter.createCounter('bound_counter').bind(labels);
for (let i = 0; i < 100; i++) {
  // this will bind each time
  counter.add(1, labels);

  // this is already bound
  boundCounter.add(1);
}

// counter has been bound 100 times and incremented 100 times
// boundCounter has been bound 1 time and incremented 100 times