Change default metrics address to localhost:8888

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>

.chloggen/change-prom-address-to-localhost.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: 'breaking'
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: service/telemetry
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: 
+
+# One or more tracking issues or pull requests related to the change
+issues: []
+
+# (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: This behavior can be disabled by disabling the feature gate 'telemetry.UseLocalHostAsDefaultMetricsAddress'.
+
+# 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, api]

service/telemetry/factory.go

@@ -18,9 +18,16 @@ import (
 	"go.opentelemetry.io/collector/service/internal/resource"
 )
 
+var useLocalHostAsDefaultMetricsAddressFeatureGate = featuregate.GlobalRegistry().MustRegister(
+	"telemetry.UseLocalHostAsDefaultMetricsAddress",
+	featuregate.StageBeta,
+	featuregate.WithRegisterFromVersion("v0.110.0"),
+	featuregate.WithRegisterDescription("controls whether default Prometheus metrics server use localhost as the default host for their endpoints"),
+)
+
 // disableHighCardinalityMetricsfeatureGate is the feature gate that controls whether the collector should enable
 // potentially high cardinality metrics. The gate will be removed when the collector allows for view configuration.
-var disableHighCardinalityMetricsfeatureGate = featuregate.GlobalRegistry().MustRegister(
+var disableHighCardinalityMetricsFeatureGate = featuregate.GlobalRegistry().MustRegister(
 	"telemetry.disableHighCardinalityMetrics",
 	featuregate.StageAlpha,
 	featuregate.WithRegisterDescription("controls whether the collector should enable potentially high"+
@@ -67,7 +74,7 @@ func NewFactory() Factory {
 		}),
 		withMeterProvider(func(_ context.Context, set Settings, cfg component.Config) (metric.MeterProvider, error) {
 			c := *cfg.(*Config)
-			disableHighCard := disableHighCardinalityMetricsfeatureGate.IsEnabled()
+			disableHighCard := disableHighCardinalityMetricsFeatureGate.IsEnabled()
 			return newMeterProvider(
 				meterProviderSettings{
 					res:               resource.New(set.BuildInfo, c.Resource),
@@ -81,6 +88,11 @@ func NewFactory() Factory {
 }
 
 func createDefaultConfig() component.Config {
+	metricsAddress := "localhost:8888"
+	if !useLocalHostAsDefaultMetricsAddressFeatureGate.IsEnabled() {
+		metricsAddress = ":8888"
+	}
+
 	return &Config{
 		Logs: LogsConfig{
 			Level:       zapcore.InfoLevel,
@@ -100,7 +112,7 @@ func createDefaultConfig() component.Config {
 		},
 		Metrics: MetricsConfig{
 			Level:   configtelemetry.LevelNormal,
-			Address: ":8888",
+			Address: metricsAddress,
 		},
 	}
 }