feat(frontend): search spans from extension tracers when object name is specified

pkg/frontend/reader/reader.go

@@ -205,6 +205,20 @@ func (reader *spanReader) FindTraces(ctx context.Context, query *spanstore.Trace
 		return nil, err
 	}
 
+	fetchFromExtension := false
+
+	if len(tts) == 0 {
+		// searched object has no events during this period,
+		// try to discover any possible spans from extensions.
+		if query.Tags["resource"] != "" && query.Tags["name"] != "" {
+			tts = append(tts, &jaegerbackend.TraceThumbnail{
+				Identifier: nil,
+				Spans:      tftree.NewSpanTree(fakeObjectSpans(query)),
+			})
+			fetchFromExtension = true
+		}
+	}
+
 	twmList := make([]merge.TraceWithMetadata[any], len(tts))
 	for i, tt := range tts {
 		twmList[i] = merge.TraceWithMetadata[any]{
@@ -245,14 +259,24 @@ func (reader *spanReader) FindTraces(ctx context.Context, query *spanstore.Trace
 	for _, mergeTree := range mergeTrees {
 		cacheId := generateCacheId(config.Id)
 
+		var cachedSpans []*model.Span
+		if fetchFromExtension {
+			rootSpan, _ := tftree.CopySpan(mergeTree.Tree.Root)
+			cachedSpans = []*model.Span{rootSpan}
+		}
+
 		trace, extensionCache, err := reader.prepareEntry(ctx, rootKey, query, mergeTree.Tree, cacheId)
 		if err != nil {
 			return nil, err
 		}
 
+		if fetchFromExtension && len(trace.Spans) <= 1 {
+			continue
+		}
+
 		traces = append(traces, trace)
 
-		cacheEntry, err := reader.prepareCache(rootKey, query, mergeTree.Metadata, cacheId, extensionCache)
+		cacheEntry, err := reader.prepareCache(rootKey, query, mergeTree.Metadata, cacheId, extensionCache, cachedSpans)
 		if err != nil {
 			return nil, err
 		}
@@ -318,6 +342,7 @@ func (reader *spanReader) prepareCache(
 	identifiers []any,
 	cacheId model.TraceID,
 	extensionCache []tracecache.ExtensionCache,
+	cachedSpans []*model.Span,
 ) (tracecache.Entry, error) {
 	identifiersJson := make([]json.RawMessage, len(identifiers))
 	for i, identifier := range identifiers {
@@ -336,6 +361,7 @@ func (reader *spanReader) prepareCache(
 			StartTime:   query.StartTimeMin,
 			EndTime:     query.StartTimeMax,
 			RootObject:  rootKey,
+			Spans:       cachedSpans,
 		},
 	}
 	if reader.options.cacheExtensions {
@@ -360,6 +386,9 @@ func (reader *spanReader) GetTrace(ctx context.Context, cacheId model.TraceID) (
 
 	traces := make([]merge.TraceWithMetadata[struct{}], 0, len(entry.Identifiers))
 	for _, identifier := range entry.Identifiers {
+		if identifier == nil || string(identifier) == "null" {
+			continue
+		}
 		trace, err := reader.Backend.Get(ctx, identifier, cacheId, entry.StartTime, entry.EndTime)
 		if err != nil {
 			return nil, fmt.Errorf("cannot fetch trace pointed by the cache: %w", err)
@@ -394,15 +423,21 @@ func (reader *spanReader) GetTrace(ctx context.Context, cacheId model.TraceID) (
 	}
 
 	// if spans were connected, they should continue to be connected since link spans cannot be deleted, so assume there is only one trace
-	if len(mergedTrees) != 1 {
+	if len(traces) != 0 && len(mergedTrees) != 1 {
 		return nil, fmt.Errorf("inconsistent linked trace count %d", len(mergedTrees))
 	}
-	mergedTree := mergedTrees[0]
+
 	aggTrace := &model.Trace{
 		ProcessMap: []model.Trace_ProcessMapping{{
 			ProcessID: "0",
 		}},
-		Spans: mergedTree.Tree.GetSpans(),
+	}
+
+	if len(mergedTrees) > 0 {
+		aggTrace.Spans = mergedTrees[0].Tree.GetSpans()
+	} else {
+		spans, _ := tftree.CopySpans(entry.Spans)
+		aggTrace.Spans = spans
 	}
 
 	var extensions transform.ExtensionProcessor = &transform.FetchExtensionsAndStoreCache{}
@@ -533,3 +568,29 @@ func mergeListWithBackend[M any](backend jaegerbackend.Backend, convertMetadata
 		return twmList, nil
 	}
 }
+
+func fakeObjectSpans(query *spanstore.TraceQueryParameters) []*model.Span {
+	tags := []model.KeyValue{
+		model.String(zconstants.TraceSource, zconstants.TraceSourceObject),
+		model.String(zconstants.PseudoType, string(zconstants.PseudoTypeObject)),
+	}
+	for tagKey, tagVal := range query.Tags {
+		tags = append(tags, model.String(tagKey, tagVal))
+	}
+
+	for _, requiredKey := range []string{"cluster", "group", "version", "resource", "namespace", "name"} {
+		if _, ok := query.Tags[requiredKey]; !ok {
+			tags = append(tags, model.String(requiredKey, query.Tags[requiredKey]))
+		}
+	}
+
+	return []*model.Span{{
+		SpanID:    model.SpanID(1),
+		Flags:     0,
+		StartTime: query.StartTimeMin,
+		Duration:  query.StartTimeMax.Sub(query.StartTimeMin),
+		Process:   &model.Process{ServiceName: fmt.Sprintf("%s %s", query.Tags["cluster"], query.Tags["resource"])},
+		ProcessID: "0",
+		Tags:      tags,
+	}}
+}

pkg/frontend/tf/tree/tree.go

@@ -83,6 +83,20 @@ func (tree *SpanTree) Clone() (*SpanTree, error) {
 	return NewSpanTree(copiedSpans), nil
 }
 
+func CopySpans(spans []*model.Span) ([]*model.Span, error) {
+	copiedSpans := make([]*model.Span, 0, len(spans))
+	for _, span := range spans {
+		spanCopy, err := CopySpan(span)
+		if err != nil {
+			return nil, err
+		}
+
+		copiedSpans = append(copiedSpans, spanCopy)
+	}
+
+	return copiedSpans, nil
+}
+
 func CopySpan(span *model.Span) (*model.Span, error) {
 	spanJson, err := json.Marshal(span)
 	if err != nil {

pkg/frontend/tracecache/interface.go

@@ -48,6 +48,7 @@ type EntryValue struct {
 	RootObject  *utilobject.Key   `json:"rootObject"`
 
 	Extensions []ExtensionCache `json:"extensions"`
+	Spans      []*model.Span    `json:"spans"`
 }
 
 type ExtensionCache struct {