Modified otel-http-server-duration from microseconds to milliseconds (#…

…1537)

* modified changelog and otel-http-server-duration from microseconds to milliseconds

* Update comments for floating point division

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

* Update CHANGELOG.md

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

* Update changelog comment location

* EOL Character

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

CHANGELOG.md

@@ -8,6 +8,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Fixed
+
+- Change the `http-server-duration` instrument in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` to record milliseconds instead of microseconds match what is specified in the OpenTelemetry specification. (#1414, #1537)
+
 ## [1.3.0/0.28.0] - 2021-12-10
 
 ### ⚠️ Notice ⚠️

instrumentation/net/http/otelhttp/handler.go

@@ -48,7 +48,7 @@ type Handler struct {
 	filters           []Filter
 	spanNameFormatter func(string, *http.Request) string
 	counters          map[string]metric.Int64Counter
-	valueRecorders    map[string]metric.Int64Histogram
+	valueRecorders    map[string]metric.Float64Histogram
 }
 
 func defaultHandlerFormatter(operation string, _ *http.Request) string {
@@ -94,15 +94,15 @@ func handleErr(err error) {
 
 func (h *Handler) createMeasures() {
 	h.counters = make(map[string]metric.Int64Counter)
-	h.valueRecorders = make(map[string]metric.Int64Histogram)
+	h.valueRecorders = make(map[string]metric.Float64Histogram)
 
 	requestBytesCounter, err := h.meter.NewInt64Counter(RequestContentLength)
 	handleErr(err)
 
 	responseBytesCounter, err := h.meter.NewInt64Counter(ResponseContentLength)
 	handleErr(err)
 
-	serverLatencyMeasure, err := h.meter.NewInt64Histogram(ServerLatency)
+	serverLatencyMeasure, err := h.meter.NewFloat64Histogram(ServerLatency)
 	handleErr(err)
 
 	h.counters[RequestContentLength] = requestBytesCounter
@@ -195,7 +195,8 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	h.counters[RequestContentLength].Add(ctx, bw.read, attributes...)
 	h.counters[ResponseContentLength].Add(ctx, rww.written, attributes...)
 
-	elapsedTime := time.Since(requestStartTime).Microseconds()
+	// Use floating point division here for higher precision (instead of Millisecond method).
+	elapsedTime := float64(time.Since(requestStartTime)) / float64(time.Millisecond)
 
 	h.valueRecorders[ServerLatency].Record(ctx, elapsedTime, attributes...)
 }