[service] Ensure a noop tracer provider is returned if no processors are configured

Previously the service was returning an instance of a SDK tracer provider regardless of whether there were any processors configured causing resources to be consumed unnecessarily.

Fixes open-telemetry#10858

Signed-off-by: Alex Boten <[email protected]>

Author: codeboten

.chloggen/codeboten_disable-tracer-without-config.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: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: service
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Ensure a noop tracer provider is returned if no processors are configured
+
+# One or more tracking issues or pull requests related to the change
+issues: [10858]
+
+# (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: Previously the service was returning an instance of a SDK tracer provider regardless of whether there were any processors configured causing resources to be consumed unnecessarily.
+
+# 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: []

service/telemetry/tracer.go

@@ -51,33 +51,38 @@ func newTracerProvider(ctx context.Context, set Settings, cfg Config) (trace.Tra
 		Attributes: attributes(set, cfg),
 	}
 
+	var tracerProviderCfg *config.TracerProvider
+	if len(cfg.Traces.Processors) > 0 {
+		tracerProviderCfg = &config.TracerProvider{
+			Processors: cfg.Traces.Processors,
+			// TODO: once https://github.com/open-telemetry/opentelemetry-configuration/issues/83 is resolved,
+			// configuration for sampler should be done here via something like the following:
+			//
+			// Sampler: &config.Sampler{
+			// 	ParentBased: &config.SamplerParentBased{
+			// 		LocalParentSampled: &config.Sampler{
+			// 			AlwaysOn: config.SamplerAlwaysOn{},
+			// 		},
+			// 		LocalParentNotSampled: &config.Sampler{
+			//	        RecordOnly: config.SamplerRecordOnly{},
+			//      },
+			// 		RemoteParentSampled: &config.Sampler{
+			// 			AlwaysOn: config.SamplerAlwaysOn{},
+			// 		},
+			// 		RemoteParentNotSampled: &config.Sampler{
+			//	        RecordOnly: config.SamplerRecordOnly{},
+			//      },
+			// 	},
+			// },
+		}
+	}
+
 	sdk, err := config.NewSDK(
 		config.WithContext(ctx),
 		config.WithOpenTelemetryConfiguration(
 			config.OpenTelemetryConfiguration{
-				Resource: &res,
-				TracerProvider: &config.TracerProvider{
-					Processors: cfg.Traces.Processors,
-					// TODO: once https://github.com/open-telemetry/opentelemetry-configuration/issues/83 is resolved,
-					// configuration for sampler should be done here via something like the following:
-					//
-					// Sampler: &config.Sampler{
-					// 	ParentBased: &config.SamplerParentBased{
-					// 		LocalParentSampled: &config.Sampler{
-					// 			AlwaysOn: config.SamplerAlwaysOn{},
-					// 		},
-					// 		LocalParentNotSampled: &config.Sampler{
-					//	        RecordOnly: config.SamplerRecordOnly{},
-					//      },
-					// 		RemoteParentSampled: &config.Sampler{
-					// 			AlwaysOn: config.SamplerAlwaysOn{},
-					// 		},
-					// 		RemoteParentNotSampled: &config.Sampler{
-					//	        RecordOnly: config.SamplerRecordOnly{},
-					//      },
-					// 	},
-					// },
-				},
+				Resource:       &res,
+				TracerProvider: tracerProviderCfg,
 			},
 		),
 	)

service/telemetry/tracer_test.go

@@ -4,12 +4,16 @@
 package telemetry // import "go.opentelemetry.io/collector/service/telemetry"
 
 import (
+	"context"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/service/telemetry/internal"
+	"go.opentelemetry.io/contrib/config"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	"go.opentelemetry.io/otel/trace/noop"
 )
 
 func TestAttributes(t *testing.T) {
@@ -56,6 +60,44 @@ func TestAttributes(t *testing.T) {
 	}
 }
 
+func TestNewTracerProvider(t *testing.T) {
+	tests := []struct {
+		name               string
+		cfg                Config
+		wantTracerProvider any
+	}{
+		{
+			name:               "no processors",
+			wantTracerProvider: noop.TracerProvider{},
+		},
+		{
+			name: "some processors",
+			cfg: Config{
+				Resource: map[string]*string{"service.name": ptr("resource.name"), "service.version": ptr("resource.version"), "test": ptr("test")},
+				Traces: TracesConfig{
+					Processors: []config.SpanProcessor{
+						{
+							Simple: &config.SimpleSpanProcessor{
+								Exporter: config.SpanExporter{
+									Console: config.Console{},
+								},
+							},
+						},
+					},
+				},
+			},
+			wantTracerProvider: &sdktrace.TracerProvider{},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			provider, err := newTracerProvider(context.TODO(), internal.Settings{}, tt.cfg)
+			require.NoError(t, err)
+			require.IsType(t, tt.wantTracerProvider, provider)
+		})
+	}
+}
+
 func ptr[T any](v T) *T {
 	return &v
 }