lib/querytracer: make it easier to use by passing trace context message to New and NewChild

The context message can be extended by calling Donef.
If there is no need to extend the message, then just call Done.

app/vmselect/main.go

@@ -148,7 +148,7 @@ func requestHandler(w http.ResponseWriter, r *http.Request) bool {
 	startTime := time.Now()
 	defer requestDuration.UpdateDuration(startTime)
 	tracerEnabled := searchutils.GetBool(r, "trace")
-	qt := querytracer.New(tracerEnabled)
+	qt := querytracer.New(tracerEnabled, r.URL.Path)
 
 	// Limit the number of concurrent queries.
 	select {

app/vmselect/netstorage/netstorage.go

@@ -198,7 +198,7 @@ var resultPool sync.Pool
 //
 // rss becomes unusable after the call to RunParallel.
 func (rss *Results) RunParallel(qt *querytracer.Tracer, f func(rs *Result, workerID uint) error) error {
-	qt = qt.NewChild()
+	qt = qt.NewChild("parallel process of fetched data")
 	defer func() {
 		putTmpBlocksFile(rss.tbf)
 		rss.tbf = nil
@@ -263,7 +263,7 @@ func (rss *Results) RunParallel(qt *querytracer.Tracer, f func(rs *Result, worke
 		close(workCh)
 	}
 	workChsWG.Wait()
-	qt.Donef("parallel process of fetched data: series=%d, samples=%d", seriesProcessedTotal, rowsProcessedTotal)
+	qt.Donef("series=%d, samples=%d", seriesProcessedTotal, rowsProcessedTotal)
 
 	return firstErr
 }
@@ -608,8 +608,8 @@ func (sbh *sortBlocksHeap) Pop() interface{} {
 
 // RegisterMetricNames registers metric names from mrs in the storage.
 func RegisterMetricNames(qt *querytracer.Tracer, at *auth.Token, mrs []storage.MetricRow, deadline searchutils.Deadline) error {
-	qt = qt.NewChild()
+	qt = qt.NewChild("register metric names")
-	defer qt.Donef("register metric names")
+	defer qt.Done()
 	// Split mrs among available vmstorage nodes.
 	mrsPerNode := make([][]storage.MetricRow, len(storageNodes))
 	for _, mr := range mrs {
@@ -646,8 +646,8 @@ func RegisterMetricNames(qt *querytracer.Tracer, at *auth.Token, mrs []storage.M
 
 // DeleteSeries deletes time series matching the given sq.
 func DeleteSeries(qt *querytracer.Tracer, at *auth.Token, sq *storage.SearchQuery, deadline searchutils.Deadline) (int, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("delete series: %s", sq)
-	defer qt.Donef("delete series: %s", sq)
+	defer qt.Done()
 	requestData := sq.Marshal(nil)
 
 	// Send the query to all the storage nodes in parallel.
@@ -685,8 +685,8 @@ func DeleteSeries(qt *querytracer.Tracer, at *auth.Token, sq *storage.SearchQuer
 
 // GetLabelsOnTimeRange returns labels for the given tr until the given deadline.
 func GetLabelsOnTimeRange(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool, tr storage.TimeRange, deadline searchutils.Deadline) ([]string, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("get labels on timeRange=%s", &tr)
-	defer qt.Donef("get labels on timeRange=%s", &tr)
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -740,8 +740,8 @@ func GetLabelsOnTimeRange(qt *querytracer.Tracer, at *auth.Token, denyPartialRes
 
 // GetGraphiteTags returns Graphite tags until the given deadline.
 func GetGraphiteTags(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool, filter string, limit int, deadline searchutils.Deadline) ([]string, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("get graphite tags: filter=%s, limit=%d", filter, limit)
-	defer qt.Donef("get graphite tags: filter=%s, limit=%d", filter, limit)
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -787,8 +787,8 @@ func hasString(a []string, s string) bool {
 
 // GetLabels returns labels until the given deadline.
 func GetLabels(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool, deadline searchutils.Deadline) ([]string, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("get labels")
-	defer qt.Donef("get labels")
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -844,8 +844,8 @@ func GetLabels(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool,
 // until the given deadline.
 func GetLabelValuesOnTimeRange(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool, labelName string,
 	tr storage.TimeRange, deadline searchutils.Deadline) ([]string, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("get values for label %s on a timeRange %s", labelName, &tr)
-	qt.Donef("get values for label %s on a timeRange %s", labelName, &tr)
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -897,8 +897,8 @@ func GetLabelValuesOnTimeRange(qt *querytracer.Tracer, at *auth.Token, denyParti
 
 // GetGraphiteTagValues returns tag values for the given tagName until the given deadline.
 func GetGraphiteTagValues(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool, tagName, filter string, limit int, deadline searchutils.Deadline) ([]string, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("get graphite tag values for tagName=%s, filter=%s, limit=%d", tagName, filter, limit)
-	defer qt.Donef("get graphite tag values for tagName=%s, filter=%s, limit=%d", tagName, filter, limit)
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -924,8 +924,8 @@ func GetGraphiteTagValues(qt *querytracer.Tracer, at *auth.Token, denyPartialRes
 // GetLabelValues returns label values for the given labelName
 // until the given deadline.
 func GetLabelValues(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool, labelName string, deadline searchutils.Deadline) ([]string, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("get values for label %s", labelName)
-	defer qt.Donef("get values for label %s", labelName)
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -980,8 +980,8 @@ func GetLabelValues(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse
 // It can be used for implementing https://graphite-api.readthedocs.io/en/latest/api.html#metrics-find
 func GetTagValueSuffixes(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool, tr storage.TimeRange, tagKey, tagValuePrefix string,
 	delimiter byte, deadline searchutils.Deadline) ([]string, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("get tag value suffixes for tagKey=%s, tagValuePrefix=%s, timeRange=%s", tagKey, tagValuePrefix, &tr)
-	defer qt.Donef("get tag value suffixes for tagKey=%s, tagValuePrefix=%s, timeRange=%s", tagKey, tagValuePrefix, &tr)
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -1029,8 +1029,8 @@ func GetTagValueSuffixes(qt *querytracer.Tracer, at *auth.Token, denyPartialResp
 
 // GetLabelEntries returns all the label entries for at until the given deadline.
 func GetLabelEntries(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool, deadline searchutils.Deadline) ([]storage.TagEntry, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("get label entries")
-	defer qt.Donef("get label entries")
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -1125,8 +1125,8 @@ func deduplicateStrings(a []string) []string {
 // GetTSDBStatusForDate returns tsdb status according to https://prometheus.io/docs/prometheus/latest/querying/api/#tsdb-stats
 func GetTSDBStatusForDate(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool,
 	deadline searchutils.Deadline, date uint64, topN, maxMetrics int) (*storage.TSDBStatus, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("get tsdb stats for date=%d, topN=%d", date, topN)
-	defer qt.Donef("get tsdb stats for date=%d, topN=%d", date, topN)
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -1223,8 +1223,8 @@ func toTopHeapEntries(m map[string]uint64, topN int) []storage.TopHeapEntry {
 // It accepts aribtrary filters on time series in sq.
 func GetTSDBStatusWithFilters(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool,
 	deadline searchutils.Deadline, sq *storage.SearchQuery, topN int) (*storage.TSDBStatus, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("get tsdb stats: %s, topN=%d", sq, topN)
-	defer qt.Donef("get tsdb stats: %s, topN=%d", sq, topN)
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -1267,8 +1267,8 @@ func GetTSDBStatusWithFilters(qt *querytracer.Tracer, at *auth.Token, denyPartia
 
 // GetSeriesCount returns the number of unique series for the given at.
 func GetSeriesCount(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool, deadline searchutils.Deadline) (uint64, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("get series count")
-	defer qt.Donef("get series count")
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return 0, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -1361,8 +1361,8 @@ var metricNamePool = &sync.Pool{
 // It is the responsibility of f to filter blocks according to the given tr.
 func ExportBlocks(qt *querytracer.Tracer, at *auth.Token, sq *storage.SearchQuery, deadline searchutils.Deadline,
 	f func(mn *storage.MetricName, b *storage.Block, tr storage.TimeRange) error) error {
-	qt = qt.NewChild()
+	qt = qt.NewChild("export blocks: %s", sq)
-	defer qt.Donef("export blocks: %s", sq)
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return fmt.Errorf("timeout exceeded before starting data export: %s", deadline.String())
 	}
@@ -1408,8 +1408,8 @@ func ExportBlocks(qt *querytracer.Tracer, at *auth.Token, sq *storage.SearchQuer
 
 // SearchMetricNames returns all the metric names matching sq until the given deadline.
 func SearchMetricNames(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool, sq *storage.SearchQuery, deadline searchutils.Deadline) ([]storage.MetricName, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("fetch metric names: %s", sq)
-	defer qt.Donef("fetch metric names: %s", sq)
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting to search metric names: %s", deadline.String())
 	}
@@ -1467,8 +1467,8 @@ func SearchMetricNames(qt *querytracer.Tracer, at *auth.Token, denyPartialRespon
 // Results.RunParallel or Results.Cancel must be called on the returned Results.
 func ProcessSearchQuery(qt *querytracer.Tracer, at *auth.Token, denyPartialResponse bool, sq *storage.SearchQuery,
 	fetchData bool, deadline searchutils.Deadline) (*Results, bool, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("fetch matching series: %s, fetchData=%v", sq, fetchData)
-	defer qt.Donef("fetch matching series: %s, fetchData=%v", sq, fetchData)
+	defer qt.Done()
 	if deadline.Exceeded() {
 		return nil, false, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
@@ -1573,11 +1573,11 @@ type storageNodesRequest struct {
 func startStorageNodesRequest(qt *querytracer.Tracer, denyPartialResponse bool, f func(qt *querytracer.Tracer, idx int, sn *storageNode) interface{}) *storageNodesRequest {
 	resultsCh := make(chan interface{}, len(storageNodes))
 	for idx, sn := range storageNodes {
-		qtChild := qt.NewChild()
+		qtChild := qt.NewChild("rpc at vmstorage %s", sn.connPool.Addr())
 		go func(idx int, sn *storageNode) {
 			result := f(qtChild, idx, sn)
 			resultsCh <- result
-			qtChild.Donef("rpc at vmstorage %s", sn.connPool.Addr())
+			qtChild.Done()
 		}(idx, sn)
 	}
 	return &storageNodesRequest{
@@ -1941,9 +1941,9 @@ func (sn *storageNode) processSearchQuery(qt *querytracer.Tracer, requestData []
 }
 
 func (sn *storageNode) execOnConnWithPossibleRetry(qt *querytracer.Tracer, funcName string, f func(bc *handshake.BufferedConn) error, deadline searchutils.Deadline) error {
-	qtChild := qt.NewChild()
+	qtChild := qt.NewChild("rpc call %s()", funcName)
 	err := sn.execOnConn(qtChild, funcName, f, deadline)
-	qtChild.Donef("rpc call %s()", funcName)
+	qtChild.Done()
 	if err == nil {
 		return nil
 	}
@@ -1954,9 +1954,9 @@ func (sn *storageNode) execOnConnWithPossibleRetry(qt *querytracer.Tracer, funcN
 		return err
 	}
 	// Repeat the query in the hope the error was temporary.
-	qtChild = qt.NewChild()
+	qtChild = qt.NewChild("retry rpc call %s() after error", funcName)
 	err = sn.execOnConn(qtChild, funcName, f, deadline)
-	qtChild.Donef("retry rpc call %s() after error", funcName)
+	qtChild.Done()
 	return err
 }
 

app/vmselect/prometheus/label_values_response.qtpl

@@ -6,7 +6,7 @@
 
 LabelValuesResponse generates response for /api/v1/label/<labelName>/values .
 See https://prometheus.io/docs/prometheus/latest/querying/api/#querying-label-values
-{% func LabelValuesResponse(isPartial bool, labelValues []string, qt *querytracer.Tracer, qtDone func()) %}
+{% func LabelValuesResponse(isPartial bool, labelValues []string, qt *querytracer.Tracer) %}
 {
 	"status":"success",
 	"isPartial":{% if isPartial %}true{% else %}false{% endif %},
@@ -18,7 +18,7 @@ See https://prometheus.io/docs/prometheus/latest/querying/api/#querying-label-va
 	]
 	{% code
 		qt.Printf("generate response for %d label values", len(labelValues))
-		qtDone()
+		qt.Done()
 	%}
 	{%= dumpQueryTrace(qt) %}
 }

app/vmselect/prometheus/label_values_response.qtpl.go

@@ -25,7 +25,7 @@ var (
 )
 
 //line app/vmselect/prometheus/label_values_response.qtpl:9
-func StreamLabelValuesResponse(qw422016 *qt422016.Writer, isPartial bool, labelValues []string, qt *querytracer.Tracer, qtDone func()) {
+func StreamLabelValuesResponse(qw422016 *qt422016.Writer, isPartial bool, labelValues []string, qt *querytracer.Tracer) {
 //line app/vmselect/prometheus/label_values_response.qtpl:9
 	qw422016.N().S(`{"status":"success","isPartial":`)
 //line app/vmselect/prometheus/label_values_response.qtpl:12
@@ -56,7 +56,7 @@ func StreamLabelValuesResponse(qw422016 *qt422016.Writer, isPartial bool, labelV
 	qw422016.N().S(`]`)
 //line app/vmselect/prometheus/label_values_response.qtpl:20
 	qt.Printf("generate response for %d label values", len(labelValues))
-	qtDone()
+	qt.Done()
 
 //line app/vmselect/prometheus/label_values_response.qtpl:23
 	streamdumpQueryTrace(qw422016, qt)
@@ -66,22 +66,22 @@ func StreamLabelValuesResponse(qw422016 *qt422016.Writer, isPartial bool, labelV
 }
 
 //line app/vmselect/prometheus/label_values_response.qtpl:25
-func WriteLabelValuesResponse(qq422016 qtio422016.Writer, isPartial bool, labelValues []string, qt *querytracer.Tracer, qtDone func()) {
+func WriteLabelValuesResponse(qq422016 qtio422016.Writer, isPartial bool, labelValues []string, qt *querytracer.Tracer) {
 //line app/vmselect/prometheus/label_values_response.qtpl:25
 	qw422016 := qt422016.AcquireWriter(qq422016)
 //line app/vmselect/prometheus/label_values_response.qtpl:25
-	StreamLabelValuesResponse(qw422016, isPartial, labelValues, qt, qtDone)
+	StreamLabelValuesResponse(qw422016, isPartial, labelValues, qt)
 //line app/vmselect/prometheus/label_values_response.qtpl:25
 	qt422016.ReleaseWriter(qw422016)
 //line app/vmselect/prometheus/label_values_response.qtpl:25
 }
 
 //line app/vmselect/prometheus/label_values_response.qtpl:25
-func LabelValuesResponse(isPartial bool, labelValues []string, qt *querytracer.Tracer, qtDone func()) string {
+func LabelValuesResponse(isPartial bool, labelValues []string, qt *querytracer.Tracer) string {
 //line app/vmselect/prometheus/label_values_response.qtpl:25
 	qb422016 := qt422016.AcquireByteBuffer()
 //line app/vmselect/prometheus/label_values_response.qtpl:25
-	WriteLabelValuesResponse(qb422016, isPartial, labelValues, qt, qtDone)
+	WriteLabelValuesResponse(qb422016, isPartial, labelValues, qt)
 //line app/vmselect/prometheus/label_values_response.qtpl:25
 	qs422016 := string(qb422016.B)
 //line app/vmselect/prometheus/label_values_response.qtpl:25

app/vmselect/prometheus/labels_response.qtpl

@@ -6,7 +6,7 @@
 
 LabelsResponse generates response for /api/v1/labels .
 See https://prometheus.io/docs/prometheus/latest/querying/api/#getting-label-names
-{% func LabelsResponse(isPartial bool, labels []string, qt *querytracer.Tracer, qtDone func()) %}
+{% func LabelsResponse(isPartial bool, labels []string, qt *querytracer.Tracer) %}
 {
 	"status":"success",
 	"isPartial":{% if isPartial %}true{% else %}false{% endif %},
@@ -18,7 +18,7 @@ See https://prometheus.io/docs/prometheus/latest/querying/api/#getting-label-nam
 	]
 	{% code
 		qt.Printf("generate response for %d labels", len(labels))
-		qtDone()
+		qt.Done()
 	%}
 	{%= dumpQueryTrace(qt) %}
 }

app/vmselect/prometheus/labels_response.qtpl.go

@@ -25,7 +25,7 @@ var (
 )
 
 //line app/vmselect/prometheus/labels_response.qtpl:9
-func StreamLabelsResponse(qw422016 *qt422016.Writer, isPartial bool, labels []string, qt *querytracer.Tracer, qtDone func()) {
+func StreamLabelsResponse(qw422016 *qt422016.Writer, isPartial bool, labels []string, qt *querytracer.Tracer) {
 //line app/vmselect/prometheus/labels_response.qtpl:9
 	qw422016.N().S(`{"status":"success","isPartial":`)
 //line app/vmselect/prometheus/labels_response.qtpl:12
@@ -56,7 +56,7 @@ func StreamLabelsResponse(qw422016 *qt422016.Writer, isPartial bool, labels []st
 	qw422016.N().S(`]`)
 //line app/vmselect/prometheus/labels_response.qtpl:20
 	qt.Printf("generate response for %d labels", len(labels))
-	qtDone()
+	qt.Done()
 
 //line app/vmselect/prometheus/labels_response.qtpl:23
 	streamdumpQueryTrace(qw422016, qt)
@@ -66,22 +66,22 @@ func StreamLabelsResponse(qw422016 *qt422016.Writer, isPartial bool, labels []st
 }
 
 //line app/vmselect/prometheus/labels_response.qtpl:25
-func WriteLabelsResponse(qq422016 qtio422016.Writer, isPartial bool, labels []string, qt *querytracer.Tracer, qtDone func()) {
+func WriteLabelsResponse(qq422016 qtio422016.Writer, isPartial bool, labels []string, qt *querytracer.Tracer) {
 //line app/vmselect/prometheus/labels_response.qtpl:25
 	qw422016 := qt422016.AcquireWriter(qq422016)
 //line app/vmselect/prometheus/labels_response.qtpl:25
-	StreamLabelsResponse(qw422016, isPartial, labels, qt, qtDone)
+	StreamLabelsResponse(qw422016, isPartial, labels, qt)
 //line app/vmselect/prometheus/labels_response.qtpl:25
 	qt422016.ReleaseWriter(qw422016)
 //line app/vmselect/prometheus/labels_response.qtpl:25
 }
 
 //line app/vmselect/prometheus/labels_response.qtpl:25
-func LabelsResponse(isPartial bool, labels []string, qt *querytracer.Tracer, qtDone func()) string {
+func LabelsResponse(isPartial bool, labels []string, qt *querytracer.Tracer) string {
 //line app/vmselect/prometheus/labels_response.qtpl:25
 	qb422016 := qt422016.AcquireByteBuffer()
 //line app/vmselect/prometheus/labels_response.qtpl:25
-	WriteLabelsResponse(qb422016, isPartial, labels, qt, qtDone)
+	WriteLabelsResponse(qb422016, isPartial, labels, qt)
 //line app/vmselect/prometheus/labels_response.qtpl:25
 	qs422016 := string(qb422016.B)
 //line app/vmselect/prometheus/labels_response.qtpl:25

app/vmselect/prometheus/prometheus.go

@@ -375,7 +375,7 @@ func exportHandler(qt *querytracer.Tracer, at *auth.Token, w http.ResponseWriter
 		if err != nil {
 			return fmt.Errorf("cannot fetch data for %q: %w", sq, err)
 		}
-		qtChild := qt.NewChild()
+		qtChild := qt.NewChild("background export format=%s", format)
 		go func() {
 			err := rss.RunParallel(qtChild, func(rs *netstorage.Result, workerID uint) error {
 				if err := bw.Error(); err != nil {
@@ -390,12 +390,12 @@ func exportHandler(qt *querytracer.Tracer, at *auth.Token, w http.ResponseWriter
 				exportBlockPool.Put(xb)
 				return nil
 			})
-			qtChild.Donef("background export format=%s", format)
+			qtChild.Done()
 			close(resultsCh)
 			doneCh <- err
 		}()
 	} else {
-		qtChild := qt.NewChild()
+		qtChild := qt.NewChild("background export format=%s", format)
 		go func() {
 			err := netstorage.ExportBlocks(qtChild, at, sq, ep.deadline, func(mn *storage.MetricName, b *storage.Block, tr storage.TimeRange) error {
 				if err := bw.Error(); err != nil {
@@ -414,7 +414,7 @@ func exportHandler(qt *querytracer.Tracer, at *auth.Token, w http.ResponseWriter
 				exportBlockPool.Put(xb)
 				return nil
 			})
-			qtChild.Donef("background export format=%s", format)
+			qtChild.Done()
 			close(resultsCh)
 			doneCh <- err
 		}()
@@ -596,10 +596,7 @@ func LabelValuesHandler(qt *querytracer.Tracer, startTime time.Time, at *auth.To
 	w.Header().Set("Content-Type", "application/json")
 	bw := bufferedwriter.Get(w)
 	defer bufferedwriter.Put(bw)
-	qtDone := func() {
+	WriteLabelValuesResponse(bw, isPartial, labelValues, qt)
-		qt.Donef("/api/v1/labels")
-	}
-	WriteLabelValuesResponse(bw, isPartial, labelValues, qt, qtDone)
 	if err := bw.Flush(); err != nil {
 		return fmt.Errorf("canot flush label values to remote client: %w", err)
 	}
@@ -862,10 +859,7 @@ func LabelsHandler(qt *querytracer.Tracer, startTime time.Time, at *auth.Token,
 	w.Header().Set("Content-Type", "application/json")
 	bw := bufferedwriter.Get(w)
 	defer bufferedwriter.Put(bw)
-	qtDone := func() {
+	WriteLabelsResponse(bw, isPartial, labels, qt)
-		qt.Donef("/api/v1/labels")
-	}
-	WriteLabelsResponse(bw, isPartial, labels, qt, qtDone)
 	if err := bw.Flush(); err != nil {
 		return fmt.Errorf("cannot send labels response to remote client: %w", err)
 	}
@@ -991,7 +985,7 @@ func SeriesHandler(qt *querytracer.Tracer, startTime time.Time, at *auth.Token,
 	}
 	sq := storage.NewSearchQuery(at.AccountID, at.ProjectID, start, end, tagFilterss, *maxSeriesLimit)
 	qtDone := func() {
-		qt.Donef("/api/v1/series: start=%d, end=%d", start, end)
+		qt.Donef("start=%d, end=%d", start, end)
 	}
 	denyPartialResponse := searchutils.GetDenyPartialResponse(r)
 	if end-start > 24*3600*1000 {
@@ -1182,7 +1176,7 @@ func QueryHandler(qt *querytracer.Tracer, startTime time.Time, at *auth.Token, w
 	bw := bufferedwriter.Get(w)
 	defer bufferedwriter.Put(bw)
 	qtDone := func() {
-		qt.Donef("/api/v1/query: query=%s, time=%d: series=%d", query, start, len(result))
+		qt.Donef("query=%s, time=%d: series=%d", query, start, len(result))
 	}
 	WriteQueryResponse(bw, ec.IsPartialResponse, result, qt, qtDone)
 	if err := bw.Flush(); err != nil {
@@ -1283,7 +1277,7 @@ func queryRangeHandler(qt *querytracer.Tracer, startTime time.Time, at *auth.Tok
 	bw := bufferedwriter.Get(w)
 	defer bufferedwriter.Put(bw)
 	qtDone := func() {
-		qt.Donef("/api/v1/query_range: start=%d, end=%d, step=%d, query=%q: series=%d", start, end, step, query, len(result))
+		qt.Donef("start=%d, end=%d, step=%d, query=%q: series=%d", start, end, step, query, len(result))
 	}
 	WriteQueryRangeResponse(bw, ec.IsPartialResponse, result, qt, qtDone)
 	if err := bw.Flush(); err != nil {

app/vmselect/promql/eval.go

@@ -210,22 +210,23 @@ func getTimestamps(start, end, step int64) []int64 {
 }
 
 func evalExpr(qt *querytracer.Tracer, ec *EvalConfig, e metricsql.Expr) ([]*timeseries, error) {
-	qt = qt.NewChild()
+	if qt.Enabled() {
+		query := e.AppendString(nil)
+		mayCache := ec.mayCache()
+		qt = qt.NewChild("eval: query=%s, timeRange=[%d..%d], step=%d, mayCache=%v", query, ec.Start, ec.End, ec.Step, mayCache)
+	}
 	rv, err := evalExprInternal(qt, ec, e)
 	if err != nil {
 		return nil, err
 	}
 	if qt.Enabled() {
-		query := e.AppendString(nil)
 		seriesCount := len(rv)
 		pointsPerSeries := 0
 		if len(rv) > 0 {
 			pointsPerSeries = len(rv[0].Timestamps)
 		}
 		pointsCount := seriesCount * pointsPerSeries
-		mayCache := ec.mayCache()
+		qt.Donef("series=%d, points=%d, pointsPerSeries=%d", seriesCount, pointsCount, pointsPerSeries)
-		qt.Donef("eval: query=%s, timeRange=[%d..%d], step=%d, mayCache=%v: series=%d, points=%d, pointsPerSeries=%d",
-			query, ec.Start, ec.End, ec.Step, mayCache, seriesCount, pointsCount, pointsPerSeries)
 	}
 	return rv, nil
 }
@@ -251,9 +252,9 @@ func evalExprInternal(qt *querytracer.Tracer, ec *EvalConfig, e metricsql.Expr)
 	if fe, ok := e.(*metricsql.FuncExpr); ok {
 		nrf := getRollupFunc(fe.Name)
 		if nrf == nil {
-			qtChild := qt.NewChild()
+			qtChild := qt.NewChild("transform %s()", fe.Name)
 			rv, err := evalTransformFunc(qtChild, ec, fe)
-			qtChild.Donef("transform %s(): series=%d", fe.Name, len(rv))
+			qtChild.Donef("series=%d", len(rv))
 			return rv, err
 		}
 		args, re, err := evalRollupFuncArgs(qt, ec, fe)
@@ -271,15 +272,15 @@ func evalExprInternal(qt *querytracer.Tracer, ec *EvalConfig, e metricsql.Expr)
 		return rv, nil
 	}
 	if ae, ok := e.(*metricsql.AggrFuncExpr); ok {
-		qtChild := qt.NewChild()
+		qtChild := qt.NewChild("aggregate %s()", ae.Name)
 		rv, err := evalAggrFunc(qtChild, ec, ae)
-		qtChild.Donef("aggregate %s(): series=%d", ae.Name, len(rv))
+		qtChild.Donef("series=%d", len(rv))
 		return rv, err
 	}
 	if be, ok := e.(*metricsql.BinaryOpExpr); ok {
-		qtChild := qt.NewChild()
+		qtChild := qt.NewChild("binary op %q", be.Op)
 		rv, err := evalBinaryOp(qtChild, ec, be)
-		qtChild.Donef("binary op %q: series=%d", be.Op, len(rv))
+		qtChild.Donef("series=%d", len(rv))
 		return rv, err
 	}
 	if ne, ok := e.(*metricsql.NumberExpr); ok {
@@ -742,8 +743,8 @@ func aggregateAbsentOverTime(ec *EvalConfig, expr metricsql.Expr, tss []*timeser
 
 func evalRollupFuncWithSubquery(qt *querytracer.Tracer, ec *EvalConfig, funcName string, rf rollupFunc, expr metricsql.Expr, re *metricsql.RollupExpr) ([]*timeseries, error) {
 	// TODO: determine whether to use rollupResultCacheV here.
-	qt = qt.NewChild()
+	qt = qt.NewChild("subquery")
-	defer qt.Donef("subquery")
+	defer qt.Done()
 	step := re.Step.Duration(ec.Step)
 	if step == 0 {
 		step = ec.Step
@@ -874,9 +875,9 @@ func evalRollupFuncWithMetricExpr(qt *querytracer.Tracer, ec *EvalConfig, funcNa
 	expr metricsql.Expr, me *metricsql.MetricExpr, iafc *incrementalAggrFuncContext, windowExpr *metricsql.DurationExpr) ([]*timeseries, error) {
 	var rollupMemorySize int64
 	window := windowExpr.Duration(ec.Step)
-	qt = qt.NewChild()
+	qt = qt.NewChild("rollup %s(): timeRange=[%d..%d], step=%d, window=%d", funcName, ec.Start, ec.End, ec.Step, window)
 	defer func() {
-		qt.Donef("rollup %s(): timeRange=[%d..%d], step=%d, window=%d, neededMemoryBytes=%d", funcName, ec.Start, ec.End, ec.Step, window, rollupMemorySize)
+		qt.Donef("neededMemoryBytes=%d", rollupMemorySize)
 	}()
 	if me.IsEmpty() {
 		return evalNumber(ec, nan), nil
@@ -994,8 +995,8 @@ func getRollupMemoryLimiter() *memoryLimiter {
 func evalRollupWithIncrementalAggregate(qt *querytracer.Tracer, funcName string, keepMetricNames bool,
 	iafc *incrementalAggrFuncContext, rss *netstorage.Results, rcs []*rollupConfig,
 	preFunc func(values []float64, timestamps []int64), sharedTimestamps []int64) ([]*timeseries, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("rollup %s() with incremental aggregation %s() over %d series", funcName, iafc.ae.Name, rss.Len())
-	defer qt.Donef("rollup %s() with incremental aggregation %s() over %d series", funcName, iafc.ae.Name, rss.Len())
+	defer qt.Done()
 	err := rss.RunParallel(qt, func(rs *netstorage.Result, workerID uint) error {
 		rs.Values, rs.Timestamps = dropStaleNaNs(funcName, rs.Values, rs.Timestamps)
 		preFunc(rs.Values, rs.Timestamps)
@@ -1029,8 +1030,8 @@ func evalRollupWithIncrementalAggregate(qt *querytracer.Tracer, funcName string,
 
 func evalRollupNoIncrementalAggregate(qt *querytracer.Tracer, funcName string, keepMetricNames bool, rss *netstorage.Results, rcs []*rollupConfig,
 	preFunc func(values []float64, timestamps []int64), sharedTimestamps []int64) ([]*timeseries, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("rollup %s() over %d series", funcName, rss.Len())
-	defer qt.Donef("rollup %s() over %d series", funcName, rss.Len())
+	defer qt.Done()
 	tss := make([]*timeseries, 0, rss.Len()*len(rcs))
 	var tssLock sync.Mutex
 	err := rss.RunParallel(qt, func(rs *netstorage.Result, workerID uint) error {

app/vmselect/promql/rollup_result_cache.go

@@ -154,10 +154,10 @@ func ResetRollupResultCache() {
 }
 
 func (rrc *rollupResultCache) Get(qt *querytracer.Tracer, ec *EvalConfig, expr metricsql.Expr, window int64) (tss []*timeseries, newStart int64) {
-	qt = qt.NewChild()
 	if qt.Enabled() {
 		query := expr.AppendString(nil)
-		defer qt.Donef("rollup cache get: query=%s, timeRange=[%d..%d], step=%d, window=%d", query, ec.Start, ec.End, ec.Step, window)
+		qt = qt.NewChild("rollup cache get: query=%s, timeRange=[%d..%d], step=%d, window=%d", query, ec.Start, ec.End, ec.Step, window)
+		defer qt.Done()
 	}
 	if !ec.mayCache() {
 		qt.Printf("do not fetch series from cache, since it is disabled in the current context")
@@ -250,10 +250,10 @@ func (rrc *rollupResultCache) Get(qt *querytracer.Tracer, ec *EvalConfig, expr m
 var resultBufPool bytesutil.ByteBufferPool
 
 func (rrc *rollupResultCache) Put(qt *querytracer.Tracer, ec *EvalConfig, expr metricsql.Expr, window int64, tss []*timeseries) {
-	qt = qt.NewChild()
 	if qt.Enabled() {
 		query := expr.AppendString(nil)
-		defer qt.Donef("rollup cache put: query=%s, timeRange=[%d..%d], step=%d, window=%d, series=%d", query, ec.Start, ec.End, ec.Step, window, len(tss))
+		qt = qt.NewChild("rollup cache put: query=%s, timeRange=[%d..%d], step=%d, window=%d, series=%d", query, ec.Start, ec.End, ec.Step, window, len(tss))
+		defer qt.Done()
 	}
 	if len(tss) == 0 || !ec.mayCache() {
 		qt.Printf("do not store series to cache, since it is disabled in the current context")

app/vmstorage/transport/server.go

@@ -482,7 +482,7 @@ func (s *Server) processVMSelectRequest(ctx *vmselectRequestCtx) error {
 	if err != nil {
 		return fmt.Errorf("cannot read traceEnabled: %w", err)
 	}
-	ctx.qt = querytracer.New(traceEnabled)
+	ctx.qt = querytracer.New(traceEnabled, "%s() at vmstorage", rpcName)
 
 	// Limit the time required for reading request args.
 	if err := ctx.bc.SetReadDeadline(time.Now().Add(5 * time.Second)); err != nil {
@@ -506,7 +506,7 @@ func (s *Server) processVMSelectRequest(ctx *vmselectRequestCtx) error {
 	}
 
 	// Finish query trace.
-	ctx.qt.Donef("%s() at vmstorage", rpcName)
+	ctx.qt.Done()
 	traceJSON := ctx.qt.ToJSON()
 	if err := ctx.writeString(traceJSON); err != nil {
 		return fmt.Errorf("cannot send trace with length %d bytes to vmselect: %w", len(traceJSON), err)

docs/README.md

@@ -1425,7 +1425,7 @@ In this case VictoriaMetrics puts query trace into `trace` field in the output J
 For example, the following command:
 
 ```bash
-curl http://localhost:8428/api/v1/query_range -d 'query=2*rand()' -d 'start=-1h' -d 'step=1m' -d 'trace=1' | jq -r '.trace'
+curl http://localhost:8428/api/v1/query_range -d 'query=2*rand()' -d 'start=-1h' -d 'step=1m' -d 'trace=1' | jq '.trace'
 ```
 
 would return the following trace:

docs/Single-server-VictoriaMetrics.md

@@ -1429,7 +1429,7 @@ In this case VictoriaMetrics puts query trace into `trace` field in the output J
 For example, the following command:
 
 ```bash
-curl http://localhost:8428/api/v1/query_range -d 'query=2*rand()' -d 'start=-1h' -d 'step=1m' -d 'trace=1' | jq -r '.trace'
+curl http://localhost:8428/api/v1/query_range -d 'query=2*rand()' -d 'start=-1h' -d 'step=1m' -d 'trace=1' | jq '.trace'
 ```
 
 would return the following trace:

lib/querytracer/tracer.go

@@ -15,16 +15,16 @@ var denyQueryTracing = flag.Bool("denyQueryTracing", false, "Whether to disable
 // Tracer represents query tracer.
 //
 // It must be created via New call.
-// Each created tracer must be finalized via Donef call.
+// Each created tracer must be finalized via Done or Donef call.
 //
 // Tracer may contain sub-tracers (branches) in order to build tree-like execution order.
 // Call Tracer.NewChild func for adding sub-tracer.
 type Tracer struct {
 	// startTime is the time when Tracer was created
 	startTime time.Time
-	// doneTime is the time when Donef was called
+	// doneTime is the time when Done or Donef was called
 	doneTime time.Time
-	// message is the message generated by Printf or Donef call.
+	// message is the message generated by NewChild, Printf or Donef call.
 	message string
 	// children is a list of children Tracer objects
 	children []*Tracer
@@ -33,16 +33,17 @@ type Tracer struct {
 	span *span
 }
 
-// New creates a new instance of the tracer.
+// New creates a new instance of the tracer with the given fmt.Sprintf(format, args...) message.
 //
 // If enabled isn't set, then all function calls to the returned object will be no-op.
 //
-// Donef must be called when the tracer should be finished.
+// Done or Donef must be called when the tracer should be finished.
-func New(enabled bool) *Tracer {
+func New(enabled bool, format string, args ...interface{}) *Tracer {
 	if *denyQueryTracing || !enabled {
 		return nil
 	}
 	return &Tracer{
+		message:   fmt.Sprintf(format, args...),
 		startTime: time.Now(),
 	}
 }
@@ -52,26 +53,43 @@ func (t *Tracer) Enabled() bool {
 	return t != nil
 }
 
-// NewChild adds a new child Tracer to t.
+// NewChild adds a new child Tracer to t with the given fmt.Sprintf(format, args...) message.
+//
+// The returned child must be closed via Done or Donef calls.
 //
 // NewChild cannot be called from concurrent goroutines.
 // Create children tracers from a single goroutine and then pass them
 // to concurrent goroutines.
-func (t *Tracer) NewChild() *Tracer {
+func (t *Tracer) NewChild(format string, args ...interface{}) *Tracer {
 	if t == nil {
 		return nil
 	}
-	if t.message != "" {
+	if !t.doneTime.IsZero() {
 		panic(fmt.Errorf("BUG: NewChild() cannot be called after Donef(%q) call", t.message))
 	}
 	child := &Tracer{
+		message:   fmt.Sprintf(format, args...),
 		startTime: time.Now(),
 	}
 	t.children = append(t.children, child)
 	return child
 }
 
-// Donef finishes t.
+// Done finishes t.
+//
+// Done cannot be called multiple times.
+// Other Tracer functions cannot be called after Done call.
+func (t *Tracer) Done() {
+	if t == nil {
+		return
+	}
+	if !t.doneTime.IsZero() {
+		panic(fmt.Errorf("BUG: Donef(%q) already called", t.message))
+	}
+	t.doneTime = time.Now()
+}
+
+// Donef appends the given fmt.Sprintf(format, args..) message to t and finished it.
 //
 // Donef cannot be called multiple times.
 // Other Tracer functions cannot be called after Donef call.
@@ -79,21 +97,21 @@ func (t *Tracer) Donef(format string, args ...interface{}) {
 	if t == nil {
 		return
 	}
-	if t.message != "" {
+	if !t.doneTime.IsZero() {
-		panic(fmt.Errorf("BUG: Donef() already called with message %q", t.message))
+		panic(fmt.Errorf("BUG: Donef(%q) already called", t.message))
 	}
-	t.message = fmt.Sprintf(format, args...)
+	t.message += ": " + fmt.Sprintf(format, args...)
 	t.doneTime = time.Now()
 }
 
-// Printf adds new message to t.
+// Printf adds new fmt.Sprintf(format, args...) message to t.
 //
 // Printf cannot be called from concurrent goroutines.
 func (t *Tracer) Printf(format string, args ...interface{}) {
 	if t == nil {
 		return
 	}
-	if t.message != "" {
+	if !t.doneTime.IsZero() {
 		panic(fmt.Errorf("BUG: Printf() cannot be called after Done(%q) call", t.message))
 	}
 	now := time.Now()
@@ -177,8 +195,8 @@ func (t *Tracer) toSpanInternal(prevTime time.Time) (*span, time.Time) {
 	// tracer with children
 	msg := t.message
 	doneTime := t.doneTime
-	if msg == "" {
+	if doneTime.IsZero() {
-		msg = "missing Tracer.Donef() call"
+		msg += ": missing Tracer.Done() call"
 		doneTime = t.getLastChildDoneTime(t.startTime)
 	}
 	d := doneTime.Sub(t.startTime)

lib/querytracer/tracer_test.go

@@ -6,21 +6,21 @@ import (
 )
 
 func TestTracerDisabled(t *testing.T) {
-	qt := New(false)
+	qt := New(false, "test")
 	if qt.Enabled() {
 		t.Fatalf("query tracer must be disabled")
 	}
-	qtChild := qt.NewChild()
+	qtChild := qt.NewChild("child done %d", 456)
 	if qtChild.Enabled() {
 		t.Fatalf("query tracer must be disabled")
 	}
 	qtChild.Printf("foo %d", 123)
-	qtChild.Donef("child done %d", 456)
+	qtChild.Done()
 	qt.Printf("parent %d", 789)
 	if err := qt.AddJSON([]byte("foobar")); err != nil {
 		t.Fatalf("unexpected error in AddJSON: %s", err)
 	}
-	qt.Donef("test")
+	qt.Done()
 	s := qt.String()
 	if s != "" {
 		t.Fatalf("unexpected trace; got %s; want empty", s)
@@ -32,20 +32,20 @@ func TestTracerDisabled(t *testing.T) {
 }
 
 func TestTracerEnabled(t *testing.T) {
-	qt := New(true)
+	qt := New(true, "test")
 	if !qt.Enabled() {
 		t.Fatalf("query tracer must be enabled")
 	}
-	qtChild := qt.NewChild()
+	qtChild := qt.NewChild("child done %d", 456)
 	if !qtChild.Enabled() {
 		t.Fatalf("child query tracer must be enabled")
 	}
 	qtChild.Printf("foo %d", 123)
-	qtChild.Donef("child done %d", 456)
+	qtChild.Done()
 	qt.Printf("parent %d", 789)
-	qt.Donef("test")
+	qt.Donef("foo %d", 33)
 	s := qt.String()
-	sExpected := `- 0ms: test
+	sExpected := `- 0ms: test: foo 33
 | - 0ms: child done 456
 | | - 0ms: foo 123
 | - 0ms: parent 789
@@ -56,9 +56,9 @@ func TestTracerEnabled(t *testing.T) {
 }
 
 func TestTracerMultiline(t *testing.T) {
-	qt := New(true)
+	qt := New(true, "line1\nline2")
 	qt.Printf("line3\nline4\n")
-	qt.Donef("line1\nline2")
+	qt.Done()
 	s := qt.String()
 	sExpected := `- 0ms: line1
 | line2
@@ -71,18 +71,18 @@ func TestTracerMultiline(t *testing.T) {
 }
 
 func TestTracerToJSON(t *testing.T) {
-	qt := New(true)
+	qt := New(true, "test")
 	if !qt.Enabled() {
 		t.Fatalf("query tracer must be enabled")
 	}
-	qtChild := qt.NewChild()
+	qtChild := qt.NewChild("child done %d", 456)
 	if !qtChild.Enabled() {
 		t.Fatalf("child query tracer must be enabled")
 	}
 	qtChild.Printf("foo %d", 123)
-	qtChild.Donef("child done %d", 456)
+	qtChild.Done()
 	qt.Printf("parent %d", 789)
-	qt.Donef("test")
+	qt.Done()
 	s := qt.ToJSON()
 	sExpected := `{"duration_msec":0,"message":"test","children":[` +
 		`{"duration_msec":0,"message":"child done 456","children":[` +
@@ -94,11 +94,11 @@ func TestTracerToJSON(t *testing.T) {
 }
 
 func TestTraceAddJSON(t *testing.T) {
-	qtChild := New(true)
+	qtChild := New(true, "child")
 	qtChild.Printf("foo")
-	qtChild.Donef("child")
+	qtChild.Done()
 	jsonTrace := qtChild.ToJSON()
-	qt := New(true)
+	qt := New(true, "parent")
 	qt.Printf("first_line")
 	if err := qt.AddJSON([]byte(jsonTrace)); err != nil {
 		t.Fatalf("unexpected error in AddJSON: %s", err)
@@ -107,7 +107,7 @@ func TestTraceAddJSON(t *testing.T) {
 	if err := qt.AddJSON(nil); err != nil {
 		t.Fatalf("unexpected error in AddJSON(nil): %s", err)
 	}
-	qt.Donef("parent")
+	qt.Done()
 	s := qt.String()
 	sExpected := `- 0ms: parent
 | - 0ms: first_line
@@ -131,15 +131,15 @@ func TestTraceAddJSON(t *testing.T) {
 }
 
 func TestTraceMissingDonef(t *testing.T) {
-	qt := New(true)
+	qt := New(true, "parent")
 	qt.Printf("parent printf")
-	qtChild := qt.NewChild()
+	qtChild := qt.NewChild("child")
 	qtChild.Printf("child printf")
 	qt.Printf("another parent printf")
 	s := qt.String()
-	sExpected := `- 0ms: missing Tracer.Donef() call
+	sExpected := `- 0ms: parent: missing Tracer.Done() call
 | - 0ms: parent printf
-| - 0ms: missing Tracer.Donef() call
+| - 0ms: child: missing Tracer.Done() call
 | | - 0ms: child printf
 | - 0ms: another parent printf
 `

lib/storage/search.go

@@ -171,8 +171,8 @@ func (s *Search) reset() {
 //
 // Init returns the upper bound on the number of found time series.
 func (s *Search) Init(qt *querytracer.Tracer, storage *Storage, tfss []*TagFilters, tr TimeRange, maxMetrics int, deadline uint64) int {
-	qt = qt.NewChild()
+	qt = qt.NewChild("init series search: filters=%s, timeRange=%s", tfss, &tr)
-	defer qt.Donef("init series search: filters=%s, timeRange=%s", tfss, &tr)
+	defer qt.Done()
 	if s.needClosing {
 		logger.Panicf("BUG: missing MustClose call before the next call to Init")
 	}

lib/storage/storage.go

@@ -1124,8 +1124,8 @@ func nextRetentionDuration(retentionMsecs int64) time.Duration {
 
 // SearchMetricNames returns metric names matching the given tfss on the given tr.
 func (s *Storage) SearchMetricNames(qt *querytracer.Tracer, tfss []*TagFilters, tr TimeRange, maxMetrics int, deadline uint64) ([]MetricName, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("search for matching metric names")
-	defer qt.Donef("search for matching metric names")
+	defer qt.Done()
 	tsids, err := s.searchTSIDs(qt, tfss, tr, maxMetrics, deadline)
 	if err != nil {
 		return nil, err
@@ -1169,8 +1169,8 @@ func (s *Storage) SearchMetricNames(qt *querytracer.Tracer, tfss []*TagFilters,
 
 // searchTSIDs returns sorted TSIDs for the given tfss and the given tr.
 func (s *Storage) searchTSIDs(qt *querytracer.Tracer, tfss []*TagFilters, tr TimeRange, maxMetrics int, deadline uint64) ([]TSID, error) {
-	qt = qt.NewChild()
+	qt = qt.NewChild("search for matching series ids")
-	defer qt.Donef("search for matching series ids")
+	defer qt.Done()
 	// Do not cache tfss -> tsids here, since the caching is performed
 	// on idb level.
 
@@ -1221,8 +1221,8 @@ var (
 //
 // This should speed-up further searchMetricNameWithCache calls for metricIDs from tsids.
 func (s *Storage) prefetchMetricNames(qt *querytracer.Tracer, tsids []TSID, deadline uint64) error {
-	qt = qt.NewChild()
+	qt = qt.NewChild("prefetch metric names for %d series ids", len(tsids))
-	defer qt.Donef("prefetch metric names for %d series ids", len(tsids))
+	defer qt.Done()
 	if len(tsids) == 0 {
 		qt.Printf("nothing to prefetch")
 		return nil