[crazy-max]

Handle empty traces without panicking during Jaeger conversion. ParseSpanStubs accepts empty or whitespace-only input, but JaegerData unconditionally accesses the first span at

buildx/util/otelutil/jaeger.go

Lines 17 to 29 in c43f837

	func (s Spans) JaegerData() JaegerData {
	roSpans := s.ReadOnlySpans()
	// fetch default service.name from default resource for backup
	var defaultServiceName string
	defaultResource := resource.Default()
	if value, exists := defaultResource.Set().Value(attribute.Key("service.name")); exists {
	defaultServiceName = value.AsString()
	}
	data := jaeger.Trace{
	TraceID: jaeger.TraceID(roSpans[0].SpanContext().TraceID().String()),
	Processes: make(map[jaeger.ProcessID]jaeger.Process),

Return an empty result instead, allowing buildx history trace to reach its existing no trace data error at

buildx/commands/history/trace.go

Lines 97 to 111 in c43f837

	spans, err := otelutil.ParseSpanStubs(io.NewSectionReader(ra, 0, ra.Size()))
	if err != nil {
	return "", nil, err
	}
	wrapper := struct {
	Data []jaeger.Trace `json:"data"`
	}{
	Data: spans.JaegerData().Data,
	}
	if len(wrapper.Data) == 0 {
	return "", nil, errors.New("no trace data")
	}

The new empty-input regression test reproduced the index-out-of-range panic before this fix. This confirms the conversion failure but doesn't establish that BuildKit currently produces empty trace blobs.

Only emit CHILD_OF references for valid parent contexts. The previous conversion at

buildx/util/otelutil/jaeger/convert.go

Lines 117 to 129 in c43f837

	var refs []Reference
	for _, link := range ss.Links() {
	refs = append(refs, Reference{
	RefType: FollowsFrom,
	TraceID: TraceID(link.SpanContext.TraceID().String()),
	SpanID: SpanID(link.SpanContext.SpanID().String()),
	})
	}
	refs = append(refs, Reference{
	RefType: ChildOf,
	TraceID: TraceID(ss.Parent().TraceID().String()),
	SpanID: SpanID(ss.Parent().SpanID().String()),
	})

adds a parent reference even for root spans, producing all-zero trace and span IDs.

This is visible in the existing bake root-span fixture at

buildx/util/otelutil/fixtures/jaeger.json

Lines 7801 to 7811 in c43f837

	{
	"traceID": "0555ce1903feb85770d102846273073b",
	"spanID": "d30eea87f2f0241d",
	"operationName": "bake",
	"references": [
	{
	"refType": "CHILD_OF",
	"traceID": "00000000000000000000000000000000",
	"spanID": "0000000000000000"
	}
	],

Remove that invalid reference while preserving valid parents, span links, and their existing order. Roots without links now serialize with "references": null, which the pinned Jaeger UI normalizes to an empty list.

[tonistiigi]

Maybe we should just remove Jaeger support?