From 9a71140445bd4c81b073a0b406ec8d9236f04124 Mon Sep 17 00:00:00 2001
From: Yanwei Guo <yanweiguo@google.com>
Date: Mon, 14 Oct 2019 15:29:32 -0700
Subject: [PATCH] add comment (#761)

---
 metrics/config.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/metrics/config.go b/metrics/config.go
index ebfa5b354..65733c265 100644
--- a/metrics/config.go
+++ b/metrics/config.go
@@ -63,6 +63,12 @@ const (
 // ExporterOptions contains options for configuring the exporter.
 type ExporterOptions struct {
 	// Domain is the metrics domain. e.g. "knative.dev". Must be present.
+	//
+	// Stackdriver uses the following format to construct full metric name:
+	//    <domain>/<component>/<metric name from View>
+	// Prometheus uses the following format to construct full metric name:
+	//    <component>_<metric name from View>
+	// Domain is actually not used if metrics backend is Prometheus.
 	Domain string
 
 	// Component is the name of the component that emits the metrics. e.g.