[reveicer/prometheusreceiver] Add feature gate for extra scrape metrics in Prometheus receiver

.chloggen/feat_prometheusreceiver-featuregate-extrascrapemetrics.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: deprecation
+
+# The name of the component, or a single word describing the area of concern, (e.g. receiver/filelog)
+component: receiver/prometheus
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add feature gate for extra scrape metrics in Prometheus receiver
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [ 44181 ]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: deprecation of extra scrape metrics in Prometheus receiver will be removed in the next major release.
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [ user ]

receiver/prometheusreceiver/config.go

@@ -39,6 +39,7 @@ type Config struct {
 	StartTimeMetricRegex string `mapstructure:"start_time_metric_regex"`
 
 	// ReportExtraScrapeMetrics - enables reporting of additional metrics for Prometheus client like scrape_body_size_bytes
+	// Deprecated: use the feature gate "receiver.prometheusreceiver.EnableReportExtraScrapeMetrics" instead.
 	ReportExtraScrapeMetrics bool `mapstructure:"report_extra_scrape_metrics"`
 
 	TargetAllocator configoptional.Optional[targetallocator.Config] `mapstructure:"target_allocator"`

receiver/prometheusreceiver/factory.go

@@ -40,6 +40,13 @@ var enableCreatedTimestampZeroIngestionGate = featuregate.GlobalRegistry().MustR
 		" Created timestamps are injected as 0 valued samples when appropriate."),
 )
 
+var enableReportExtraScrapeMetricsGate = featuregate.GlobalRegistry().MustRegister(
+	"receiver.prometheusreceiver.EnableReportExtraScrapeMetrics",
+	featuregate.StageAlpha,
+	featuregate.WithRegisterDescription("Enables reporting of extra scrape metrics."+
+		" Extra scrape metrics are metrics that are not scraped by Prometheus but are reported by the Prometheus server."),
+)
+
 // NewFactory creates a new Prometheus receiver factory.
 func NewFactory() receiver.Factory {
 	return receiver.NewFactory(

receiver/prometheusreceiver/metrics_receiver.go

@@ -227,7 +227,7 @@ func (r *pReceiver) initPrometheusComponents(ctx context.Context, logger *slog.L
 func (r *pReceiver) initScrapeOptions() *scrape.Options {
 	opts := &scrape.Options{
 		PassMetadataInContext: true,
-		ExtraMetrics:          r.cfg.ReportExtraScrapeMetrics,
+		ExtraMetrics:          enableReportExtraScrapeMetricsGate.IsEnabled() || r.cfg.ReportExtraScrapeMetrics,
 		HTTPClientOptions: []commonconfig.HTTPClientOption{
 			commonconfig.WithUserAgent(r.settings.BuildInfo.Command + "/" + r.settings.BuildInfo.Version),
 		},

receiver/prometheusreceiver/metrics_receiver_report_extra_scrape_metrics_test.go

@@ -10,6 +10,7 @@ import (
 	"github.com/stretchr/testify/require"
 	"go.opentelemetry.io/collector/component/componenttest"
 	"go.opentelemetry.io/collector/consumer/consumertest"
+	"go.opentelemetry.io/collector/featuregate"
 	"go.opentelemetry.io/collector/pdata/pmetric"
 	"go.opentelemetry.io/collector/receiver/receivertest"
 
@@ -53,12 +54,14 @@ func testScraperMetrics(t *testing.T, targets []*testData, reportExtraScrapeMetr
 	require.NoErrorf(t, err, "Failed to create Prometheus config: %v", err)
 	defer mp.Close()
 
+	err = featuregate.GlobalRegistry().Set("receiver.prometheusreceiver.EnableReportExtraScrapeMetrics", reportExtraScrapeMetrics)
+	require.NoError(t, err)
+
 	cms := new(consumertest.MetricsSink)
 	receiver, err := newPrometheusReceiver(receivertest.NewNopSettings(metadata.Type), &Config{
-		PrometheusConfig:         cfg,
-		UseStartTimeMetric:       false,
-		StartTimeMetricRegex:     "",
-		ReportExtraScrapeMetrics: reportExtraScrapeMetrics,
+		PrometheusConfig:     cfg,
+		UseStartTimeMetric:   false,
+		StartTimeMetricRegex: "",
 	}, cms)
 	require.NoError(t, err, "Failed to create Prometheus receiver: %v", err)
 
@@ -69,6 +72,8 @@ func testScraperMetrics(t *testing.T, targets []*testData, reportExtraScrapeMetr
 		assert.Lenf(t, flattenTargets(receiver.scrapeManager.TargetsAll()), len(targets), "expected %v targets to be running", len(targets))
 		require.NoError(t, receiver.Shutdown(t.Context()))
 		assert.Empty(t, flattenTargets(receiver.scrapeManager.TargetsAll()), "expected scrape manager to have no targets")
+		err := featuregate.GlobalRegistry().Set("receiver.prometheusreceiver.EnableReportExtraScrapeMetrics", false)
+		require.NoError(t, err)
 	})
 
 	// waitgroup Wait() is strictly from a server POV indicating the sufficient number and type of requests have been seen