[chore][exporter/datadog] Only start hostmetadata.Reporter if `host…

…_metadata.enabled` (open-telemetry#36669)

#### Description

This PR avoids creating an `inframetadata.Reporter` and starting the
metadata-sending goroutine when `host_metadata.enabled` is `false`, and
removes some code that was used to work around the previous behavior.
See tracking issue for context.

When `enabled` is `false`, we leave the `exporter.metadataReporter`
field as `nil`. The parts of the code accessing this field were already
gated behind `enabled: true`, or `only_metadata: true` (which, in a
valid config, implies `enabled: false`), so it should not cause issues.
However, tests that modify the config after the exporter is created, or
which manually create invalid `Config` structs may encounter segfaults.
I assumed we do not mind segfaults in cases of incorrect internal use,
and fixed the one test that was failing because of this.

#### Link to tracking issue
Fixes open-telemetry#36522

exporter/datadogexporter/factory.go

@@ -270,10 +270,14 @@ func (f *factory) createMetricsExporter(
 	statsv := set.BuildInfo.Command + set.BuildInfo.Version
 	f.consumeStatsPayload(ctx, &wg, statsIn, statsWriter, statsv, acfg.AgentVersion, set.Logger)
 	pcfg := newMetadataConfigfromConfig(cfg)
-	metadataReporter, err := f.Reporter(set, pcfg)
-	if err != nil {
-		cancel()
-		return nil, fmt.Errorf("failed to build host metadata reporter: %w", err)
+	// Don't start a `Reporter` if host metadata is disabled.
+	var metadataReporter *inframetadata.Reporter
+	if cfg.HostMetadata.Enabled {
+		metadataReporter, err = f.Reporter(set, pcfg)
+		if err != nil {
+			cancel()
+			return nil, fmt.Errorf("failed to build host metadata reporter: %w", err)
+		}
 	}
 
 	if cfg.OnlyMetadata {
@@ -375,10 +379,14 @@ func (f *factory) createTracesExporter(
 	}
 
 	pcfg := newMetadataConfigfromConfig(cfg)
-	metadataReporter, err := f.Reporter(set, pcfg)
-	if err != nil {
-		cancel()
-		return nil, fmt.Errorf("failed to build host metadata reporter: %w", err)
+	// Don't start a `Reporter` if host metadata is disabled.
+	var metadataReporter *inframetadata.Reporter
+	if cfg.HostMetadata.Enabled {
+		metadataReporter, err = f.Reporter(set, pcfg)
+		if err != nil {
+			cancel()
+			return nil, fmt.Errorf("failed to build host metadata reporter: %w", err)
+		}
 	}
 
 	if cfg.OnlyMetadata {
@@ -463,10 +471,14 @@ func (f *factory) createLogsExporter(
 	// cancel() runs on shutdown
 
 	pcfg := newMetadataConfigfromConfig(cfg)
-	metadataReporter, err := f.Reporter(set, pcfg)
-	if err != nil {
-		cancel()
-		return nil, fmt.Errorf("failed to build host metadata reporter: %w", err)
+	// Don't start a `Reporter` if host metadata is disabled.
+	var metadataReporter *inframetadata.Reporter
+	if cfg.HostMetadata.Enabled {
+		metadataReporter, err = f.Reporter(set, pcfg)
+		if err != nil {
+			cancel()
+			return nil, fmt.Errorf("failed to build host metadata reporter: %w", err)
+		}
 	}
 
 	attributesTranslator, err := f.AttributesTranslator(set.TelemetrySettings)

exporter/datadogexporter/logs_exporter_test.go

@@ -230,9 +230,6 @@ func TestLogsExporter(t *testing.T) {
 						Endpoint: server.URL,
 					},
 				},
-				HostMetadata: HostMetadataConfig{
-					ReporterPeriod: 30 * time.Minute,
-				},
 			}
 
 			params := exportertest.NewNopSettings()
@@ -598,9 +595,6 @@ func TestLogsAgentExporter(t *testing.T) {
 					CompressionLevel: 6,
 					BatchWait:        1,
 				},
-				HostMetadata: HostMetadataConfig{
-					ReporterPeriod: 30 * time.Minute,
-				},
 			}
 			params := exportertest.NewNopSettings()
 			f := NewFactory()

exporter/datadogexporter/metrics_exporter_test.go

@@ -59,10 +59,13 @@ func TestNewExporter(t *testing.T) {
 			},
 		},
 		HostMetadata: HostMetadataConfig{
+			Enabled:        true,
 			ReporterPeriod: 30 * time.Minute,
+			HostnameSource: HostnameSourceFirstResource,
 		},
 	}
 	cfg.HostMetadata.SetSourceTimeout(50 * time.Millisecond)
+
 	params := exportertest.NewNopSettings()
 	f := NewFactory()
 
@@ -76,8 +79,6 @@ func TestNewExporter(t *testing.T) {
 	require.NoError(t, err)
 	assert.Empty(t, server.MetadataChan)
 
-	cfg.HostMetadata.Enabled = true
-	cfg.HostMetadata.HostnameSource = HostnameSourceFirstResource
 	testMetrics = pmetric.NewMetrics()
 	testutil.TestMetrics.CopyTo(testMetrics)
 	err = exp.ConsumeMetrics(context.Background(), testMetrics)
@@ -440,7 +441,9 @@ func TestNewExporter_Zorkian(t *testing.T) {
 			},
 		},
 		HostMetadata: HostMetadataConfig{
+			Enabled:        true,
 			ReporterPeriod: 30 * time.Minute,
+			HostnameSource: HostnameSourceFirstResource,
 		},
 	}
 	params := exportertest.NewNopSettings()
@@ -456,8 +459,6 @@ func TestNewExporter_Zorkian(t *testing.T) {
 	require.NoError(t, err)
 	assert.Empty(t, server.MetadataChan)
 
-	cfg.HostMetadata.Enabled = true
-	cfg.HostMetadata.HostnameSource = HostnameSourceFirstResource
 	testMetrics = pmetric.NewMetrics()
 	testutil.TestMetrics.CopyTo(testMetrics)
 	err = exp.ConsumeMetrics(context.Background(), testMetrics)

exporter/datadogexporter/traces_exporter_test.go

@@ -145,9 +145,6 @@ func TestTracesSource(t *testing.T) {
 				IgnoreResources: []string{},
 			},
 		},
-		HostMetadata: HostMetadataConfig{
-			ReporterPeriod: 30 * time.Minute,
-		},
 	}
 
 	assert := assert.New(t)
@@ -270,9 +267,6 @@ func TestTraceExporter(t *testing.T) {
 			},
 			TraceBuffer: 2,
 		},
-		HostMetadata: HostMetadataConfig{
-			ReporterPeriod: 30 * time.Minute,
-		},
 	}
 	cfg.Traces.SetFlushInterval(0.1)
 
@@ -298,11 +292,7 @@ func TestNewTracesExporter(t *testing.T) {
 	metricsServer := testutil.DatadogServerMock()
 	defer metricsServer.Close()
 
-	cfg := &Config{
-		HostMetadata: HostMetadataConfig{
-			ReporterPeriod: 30 * time.Minute,
-		},
-	}
+	cfg := &Config{}
 	cfg.API.Key = "ddog_32_characters_long_api_key1"
 	cfg.Metrics.TCPAddrConfig.Endpoint = metricsServer.URL
 	params := exportertest.NewNopSettings()
@@ -368,9 +358,6 @@ func TestPushTraceData_NewEnvConvention(t *testing.T) {
 		Traces: TracesConfig{
 			TCPAddrConfig: confignet.TCPAddrConfig{Endpoint: server.URL},
 		},
-		HostMetadata: HostMetadataConfig{
-			ReporterPeriod: 30 * time.Minute,
-		},
 	}
 	cfg.Traces.SetFlushInterval(0.1)