Prometheus Metrics Usage

1. For number of requests, use value as 1 for each request:

   metric.Must(global.GetMeterProvider().Meter("radius-rp")).NewInt64ValueRecorder(requestMetricName, metric.WithUnit(unit.Dimensionless)).Record(r.Context(), int64(1))

2. To record latency:

   metric.Must(global.GetMeterProvider().Meter("radius-rp")).NewInt64Counter(metricName, metric.WithUnit(unit.millisecond)).Add(ctx, int64(val), labels...)

3. To use a gauge, define a call back function:

   callback := func(v int) metric.Int64ObserverFunc { return metric.Int64ObserverFunc(func(_ context.Context, result metric.Int64ObserverResult) { result.Observe(int64(v), labels...) }) }(val)

   getMeterMust().NewInt64ValueObserver(metricName, callback).Observation(int64(val))