Add comment why histogram might already exists in metricsprocessor (#250

)

pkg/otelcollector/metricsprocessor/processor.go

@@ -56,7 +56,11 @@ func (p *metricsProcessor) registerRequestLatencyHistogram() error {
 	err := p.cfg.promRegistry.Register(p.workloadLatencyHistogram)
 	if err != nil {
 		if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
-			// A histogram for that metric has been registered before. Use the old histogram from now on.
+			// We're registering this histogram vec from multiple processors
+			// (logs processor and traces processor), so if both processors are
+			// enabled, it's expected that whichever processor is created
+			// second, it will see that the histogram vec was already
+			// registered. Use the existing histogram vec from now on.
 			p.workloadLatencyHistogram = are.ExistingCollector.(*prometheus.HistogramVec)
 			return nil
 		}