Fix panic when telemetry metrics are disabled

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### 🧰 Bug fixes 🧰
+
+- Fix Collector panic when disabling telemetry metrics (#5642)
+
 ## v0.55.0 Beta
 
 ### 🛑 Breaking changes 🛑

service/collector_test.go

@@ -347,6 +347,29 @@ func TestCollectorStartWithOpenTelemetryMetrics(t *testing.T) {
 	}
 }
 
+func TestCollectorWithNoMetrics(t *testing.T) {
+	factories, err := componenttest.NopFactories()
+	require.NoError(t, err)
+
+	cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nometrics.yaml")}))
+	require.NoError(t, err)
+
+	set := CollectorSettings{
+		BuildInfo:      component.NewDefaultBuildInfo(),
+		Factories:      factories,
+		ConfigProvider: cfgProvider,
+		telemetry:      newColTelemetry(featuregate.NewRegistry()),
+	}
+	col, err := New(set)
+	require.NoError(t, err)
+
+	wg := startCollector(context.Background(), t, col)
+
+	col.Shutdown()
+	wg.Wait()
+	assert.Equal(t, Closed, col.GetState())
+}
+
 func TestCollectorShutdownBeforeRun(t *testing.T) {
 	factories, err := componenttest.NopFactories()
 	require.NoError(t, err)

service/service.go

@@ -24,6 +24,7 @@ import (
 	"go.uber.org/zap"
 
 	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/config/configtelemetry"
 	"go.opentelemetry.io/collector/service/internal"
 	"go.opentelemetry.io/collector/service/internal/extensions"
 	"go.opentelemetry.io/collector/service/internal/pipelines"
@@ -97,9 +98,11 @@ func newService(set *settings) (*service, error) {
 		return nil, fmt.Errorf("cannot build pipelines: %w", err)
 	}
 
-	// The process telemetry initialization requires the ballast size, which is available after the extensions are initialized.
-	if err = telemetry.RegisterProcessMetrics(srv.telemetryInitializer.ocRegistry, getBallastSize(srv.host)); err != nil {
-		return nil, fmt.Errorf("failed to register process metrics: %w", err)
+	if set.Config.Telemetry.Metrics.Level != configtelemetry.LevelNone && set.Config.Telemetry.Metrics.Address != "" {
+		// The process telemetry initialization requires the ballast size, which is available after the extensions are initialized.
+		if err = telemetry.RegisterProcessMetrics(srv.telemetryInitializer.ocRegistry, getBallastSize(srv.host)); err != nil {
+			return nil, fmt.Errorf("failed to register process metrics: %w", err)
+		}
 	}
 
 	return srv, nil

service/testdata/otelcol-nometrics.yaml

@@ -0,0 +1,14 @@
+receivers:
+  nop:
+
+exporters:
+  nop:
+
+service:
+  telemetry:
+    metrics:
+      level: none
+  pipelines:
+    metrics:
+      receivers: [nop]
+      exporters: [nop]