Fix panic when telemetry metrics are disabled (open-telemetry#5642)

* [service] Add unit test for running the Collector with telemetry metrics disabled

* Only register process metrics when telemetry metrics are enabled

* Restore `require.NoPanics` assertion

* Delete host_test.go.bak

* Add unit test when address is empty

* Address review comment

oops

CHANGELOG.md

@@ -6,6 +6,10 @@
 
 - Add `linux-ppc64le` architecture to cross build tests in CI
 
+### 🧰 Bug fixes 🧰
+
+- Fix Collector panic when disabling telemetry metrics (#5642)
+
 ## v0.55.0 Beta
 
 ### 🛑 Breaking changes 🛑

service/collector_test.go

@@ -347,6 +347,40 @@ func TestCollectorStartWithOpenTelemetryMetrics(t *testing.T) {
 	}
 }
 
+func TestCollectorRun(t *testing.T) {
+	tests := []struct {
+		file string
+	}{
+		{file: "otelcol-nometrics.yaml"},
+		{file: "otelcol-noaddress.yaml"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.file, func(t *testing.T) {
+			factories, err := componenttest.NopFactories()
+			require.NoError(t, err)
+
+			cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", tt.file)}))
+			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-noaddress.yaml

@@ -0,0 +1,14 @@
+receivers:
+  nop:
+
+exporters:
+  nop:
+
+service:
+  telemetry:
+    metrics:
+      address: ""
+  pipelines:
+    metrics:
+      receivers: [nop]
+      exporters: [nop]

service/testdata/otelcol-nometrics.yaml

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