Move OpenMetrics options to a separate struct

Signed-off-by: Arthur Silva Sens <arthur.sens@coralogix.com>

Author: Arthur Silva Sens

examples/createdtimestamps/main.go

@@ -51,8 +51,10 @@ func main() {
 		"/metrics", promhttp.HandlerFor(
 			registry,
 			promhttp.HandlerOpts{
-				EnableOpenMetrics:               true,
-				EnableOpenMetricsCreatedMetrics: true,
+				OpenMetricsOptions: promhttp.OpenMetricsOptions{
+					EnableOpenMetrics:               true,
+					EnableOpenMetricsCreatedMetrics: true,
+				},
 			}),
 	)
 	// To test: curl -H 'Accept: application/openmetrics-text' localhost:8080/metrics

examples/exemplars/main.go

@@ -61,7 +61,9 @@ func main() {
 		"/metrics", promhttp.HandlerFor(
 			registry,
 			promhttp.HandlerOpts{
-				EnableOpenMetrics: true,
+				OpenMetricsOptions: promhttp.OpenMetricsOptions{
+					EnableOpenMetrics: true,
+				},
 			}),
 	)
 	// To test: curl -H 'Accept: application/openmetrics-text' localhost:8080/metrics

prometheus/promhttp/http.go

@@ -160,7 +160,7 @@ func HandlerForTransactional(reg prometheus.TransactionalGatherer, opts HandlerO
 		}
 
 		var contentType expfmt.Format
-		if opts.EnableOpenMetrics {
+		if opts.EnableOpenMetrics || opts.OpenMetricsOptions.EnableOpenMetrics {
 			contentType = expfmt.NegotiateIncludingOpenMetrics(req.Header)
 		} else {
 			contentType = expfmt.Negotiate(req.Header)
@@ -181,7 +181,7 @@ func HandlerForTransactional(reg prometheus.TransactionalGatherer, opts HandlerO
 		}
 
 		var enc expfmt.Encoder
-		if opts.EnableOpenMetricsCreatedMetrics {
+		if opts.OpenMetricsOptions.EnableOpenMetricsCreatedMetrics {
 			enc = expfmt.NewEncoder(w, contentType, expfmt.WithCreatedLines())
 		} else {
 			enc = expfmt.NewEncoder(w, contentType)
@@ -366,6 +366,32 @@ type HandlerOpts struct {
 	// away). Until the implementation is improved, it is recommended to
 	// implement a separate timeout in potentially slow Collectors.
 	Timeout time.Duration
+	// If true, the experimental OpenMetrics encoding is added to the
+	// possible options during content negotiation. Note that Prometheus
+	// 2.5.0+ will negotiate OpenMetrics as first priority. OpenMetrics is
+	// the only way to transmit exemplars. However, the move to OpenMetrics
+	// is not completely transparent. Most notably, the values of "quantile"
+	// labels of Summaries and "le" labels of Histograms are formatted with
+	// a trailing ".0" if they would otherwise look like integer numbers
+	// (which changes the identity of the resulting series on the Prometheus
+	// server).
+	//
+	// Deprecated: Use OpenMetricsOptions.EnableOpenMetrics instead.
+	EnableOpenMetrics bool
+	// OpenMetricsOptions holds settings for the experimental OpenMetrics encoding.
+	// It can be used to enable OpenMetrics encoding and for setting extra options.
+	OpenMetricsOptions OpenMetricsOptions
+	// ProcessStartTime allows setting process start timevalue that will be exposed
+	// with "Process-Start-Time-Unix" response header along with the metrics
+	// payload. This allow callers to have efficient transformations to cumulative
+	// counters (e.g. OpenTelemetry) or generally _created timestamp estimation per
+	// scrape target.
+	// NOTE: This feature is experimental and not covered by OpenMetrics or Prometheus
+	// exposition format.
+	ProcessStartTime time.Time
+}
+
+type OpenMetricsOptions struct {
 	// If true, the experimental OpenMetrics encoding is added to the
 	// possible options during content negotiation. Note that Prometheus
 	// 2.5.0+ will negotiate OpenMetrics as first priority. OpenMetrics is
@@ -391,14 +417,6 @@ type HandlerOpts struct {
 	// _created lines will result in increased cardinality and no improvements
 	// in reset detection.
 	EnableOpenMetricsCreatedMetrics bool
-	// ProcessStartTime allows setting process start timevalue that will be exposed
-	// with "Process-Start-Time-Unix" response header along with the metrics
-	// payload. This allow callers to have efficient transformations to cumulative
-	// counters (e.g. OpenTelemetry) or generally _created timestamp estimation per
-	// scrape target.
-	// NOTE: This feature is experimental and not covered by OpenMetrics or Prometheus
-	// exposition format.
-	ProcessStartTime time.Time
 }
 
 // gzipAccepted returns whether the client will accept gzip-encoded content.