feat(otel): emit gotenberg.startup span with engine versions

cmd/gotenberg.go

@@ -192,6 +192,9 @@ func Run() {
 	if parsedFlags.MustBool("gotenberg-build-debug-data") {
 		// Build the debug data.
 		gotenberg.BuildDebug(ctx)
+
+		// Surface engine versions per trace once modules have reported them.
+		gotenberg.EmitStartupSpan(context.Background())
 	}
 
 	quit := make(chan os.Signal, 1)

pkg/gotenberg/startup_test.go

@@ -0,0 +1,59 @@
+package gotenberg
+
+import (
+	"context"
+	"testing"
+)
+
+func TestDebugModuleVersion(t *testing.T) {
+	info := DebugInfo{
+		ModulesAdditionalData: map[string]map[string]any{
+			"chromium": {"version": "Chromium 145.0"},
+			"broken":   {"version": 42},
+		},
+	}
+
+	if got := debugModuleVersion(info, "chromium"); got != "Chromium 145.0" {
+		t.Errorf("expected chromium version, got %q", got)
+	}
+	if got := debugModuleVersion(info, "missing"); got != "" {
+		t.Errorf("expected empty for a missing module, got %q", got)
+	}
+	if got := debugModuleVersion(info, "broken"); got != "" {
+		t.Errorf("expected empty for a non-string version, got %q", got)
+	}
+}
+
+func TestEmitStartupSpan(t *testing.T) {
+	recorder := newTestSpanRecorder(t)
+
+	debugMu.Lock()
+	previous := debug
+	debug = &DebugInfo{
+		Version: "v8.0.0",
+		ModulesAdditionalData: map[string]map[string]any{
+			"chromium":        {"version": "Chromium 145.0"},
+			"libreoffice-api": {"version": "LibreOffice 24.8"},
+		},
+	}
+	debugMu.Unlock()
+	t.Cleanup(func() {
+		debugMu.Lock()
+		debug = previous
+		debugMu.Unlock()
+	})
+
+	EmitStartupSpan(context.Background())
+
+	span := findSpan(recorder, "gotenberg.startup")
+	if span == nil {
+		t.Fatal("expected a gotenberg.startup span to be recorded")
+	}
+
+	if v, ok := spanAttr(span, "gotenberg.chromium.version"); !ok || v.AsString() != "Chromium 145.0" {
+		t.Errorf("expected gotenberg.chromium.version=Chromium 145.0, got %q (present=%t)", v.AsString(), ok)
+	}
+	if v, ok := spanAttr(span, "gotenberg.libreoffice.version"); !ok || v.AsString() != "LibreOffice 24.8" {
+		t.Errorf("expected gotenberg.libreoffice.version=LibreOffice 24.8, got %q (present=%t)", v.AsString(), ok)
+	}
+}

pkg/gotenberg/telemetry.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/hashicorp/go-retryablehttp"
 	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/metric"
 	"go.opentelemetry.io/otel/trace"
 
@@ -188,6 +189,46 @@ func Meter() metric.Meter {
 	)
 }
 
+// EmitStartupSpan records a single gotenberg.startup span carrying static,
+// process-wide attributes that are only known once modules are provisioned,
+// such as the chromium and libreoffice binary versions gathered by
+// [BuildDebug]. It surfaces version data per trace without re-detecting it on
+// every conversion. The engine versions live here, on a span, rather than on
+// the resource because the resource is built before modules report them.
+func EmitStartupSpan(ctx context.Context) {
+	info := Debug()
+
+	var attrs []attribute.KeyValue
+	if v := debugModuleVersion(info, "chromium"); v != "" {
+		attrs = append(attrs, attribute.String("gotenberg.chromium.version", v))
+	}
+	if v := debugModuleVersion(info, "libreoffice-api"); v != "" {
+		attrs = append(attrs, attribute.String("gotenberg.libreoffice.version", v))
+	}
+
+	_, span := Tracer().Start(ctx, "gotenberg.startup",
+		trace.WithSpanKind(trace.SpanKindInternal),
+		trace.WithAttributes(attrs...),
+	)
+	span.End()
+}
+
+// debugModuleVersion returns the "version" entry reported by the module with
+// the given ID, or an empty string when it is missing.
+func debugModuleVersion(info DebugInfo, moduleID string) string {
+	data, ok := info.ModulesAdditionalData[moduleID]
+	if !ok {
+		return ""
+	}
+
+	version, ok := data["version"].(string)
+	if !ok {
+		return ""
+	}
+
+	return version
+}
+
 // LeveledLogger is a wrapper around a [slog.Logger] so that it may be used by a
 // [retryablehttp.Client].
 type LeveledLogger struct {