refactor(otel): extract shared buildResource helper

pkg/gotenberg/internal/otel/otel.go

@@ -20,11 +20,9 @@ import (
 	semconv "go.opentelemetry.io/otel/semconv/v1.41.0"
 )
 
-// InitTracerProvider initializes the OpenTelemetry tracer provider.
+// buildResource assembles the OpenTelemetry resource shared by the tracer,
-func InitTracerProvider(logger *slog.Logger, serviceName, serviceVersion string) (shutdown func(context.Context) error, err error) {
+// meter, and logger providers.
-	initOtelLogger(logger)
+func buildResource(serviceName, serviceVersion string) (*resource.Resource, error) {
-
-	ctx := context.Background()
 	hostname, err := os.Hostname()
 	if err != nil {
 		return nil, fmt.Errorf("get hostname: %w", err)
@@ -43,6 +41,20 @@ func InitTracerProvider(logger *slog.Logger, serviceName, serviceVersion string)
 		return nil, fmt.Errorf("merge resource: %w", err)
 	}
 
+	return res, nil
+}
+
+// InitTracerProvider initializes the OpenTelemetry tracer provider.
+func InitTracerProvider(logger *slog.Logger, serviceName, serviceVersion string) (shutdown func(context.Context) error, err error) {
+	initOtelLogger(logger)
+
+	ctx := context.Background()
+
+	res, err := buildResource(serviceName, serviceVersion)
+	if err != nil {
+		return nil, fmt.Errorf("build resource: %w", err)
+	}
+
 	traceOpts := []trace.TracerProviderOption{
 		trace.WithResource(res),
 	}
@@ -72,22 +84,10 @@ func InitMeterProvider(logger *slog.Logger, serviceName, serviceVersion string)
 	initOtelLogger(logger)
 
 	ctx := context.Background()
-	hostname, err := os.Hostname()
-	if err != nil {
-		return nil, fmt.Errorf("get hostname: %w", err)
-	}
 
-	res, err := resource.Merge(
+	res, err := buildResource(serviceName, serviceVersion)
-		resource.Default(),
-		resource.NewWithAttributes(
-			semconv.SchemaURL,
-			semconv.ServiceName(serviceName),
-			semconv.ServiceVersion(serviceVersion),
-			semconv.HostName(hostname),
-		),
-	)
 	if err != nil {
-		return nil, fmt.Errorf("merge resource: %w", err)
+		return nil, fmt.Errorf("build resource: %w", err)
 	}
 
 	metricOpts := []metric.Option{
@@ -126,22 +126,10 @@ func InitLoggerProvider(logger *slog.Logger, serviceName, serviceVersion string)
 	initOtelLogger(logger)
 
 	ctx := context.Background()
-	hostname, err := os.Hostname()
-	if err != nil {
-		return nil, nil, fmt.Errorf("get hostname: %w", err)
-	}
 
-	res, err := resource.Merge(
+	res, err := buildResource(serviceName, serviceVersion)
-		resource.Default(),
-		resource.NewWithAttributes(
-			semconv.SchemaURL,
-			semconv.ServiceName(serviceName),
-			semconv.ServiceVersion(serviceVersion),
-			semconv.HostName(hostname),
-		),
-	)
 	if err != nil {
-		return nil, nil, fmt.Errorf("merge resource: %w", err)
+		return nil, nil, fmt.Errorf("build resource: %w", err)
 	}
 
 	logOpts := []log.LoggerProviderOption{

pkg/gotenberg/internal/otel/otel_test.go

@@ -11,8 +11,31 @@ import (
 	"go.opentelemetry.io/otel/sdk/metric/exemplar"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	semconv "go.opentelemetry.io/otel/semconv/v1.41.0"
 )
 
+func TestBuildResource(t *testing.T) {
+	res, err := buildResource("gotenberg", "v8.0.0")
+	if err != nil {
+		t.Fatalf("build resource: %v", err)
+	}
+
+	got := map[string]string{}
+	for _, kv := range res.Attributes() {
+		got[string(kv.Key)] = kv.Value.AsString()
+	}
+
+	if got[string(semconv.ServiceNameKey)] != "gotenberg" {
+		t.Errorf("service.name = %q, want %q", got[string(semconv.ServiceNameKey)], "gotenberg")
+	}
+	if got[string(semconv.ServiceVersionKey)] != "v8.0.0" {
+		t.Errorf("service.version = %q, want %q", got[string(semconv.ServiceVersionKey)], "v8.0.0")
+	}
+	if _, ok := got[string(semconv.HostNameKey)]; !ok {
+		t.Error("expected host.name attribute to be present")
+	}
+}
+
 // TestInitTracerProvider_HonorsSamplerEnv guards the contract that the tracer
 // provider keeps honoring OTEL_TRACES_SAMPLER. The SDK reads it only when no
 // explicit sampler is configured, so any future WithSampler() would silently