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chore: Add trace spans for query-frontend #4620

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Nov 17, 2025
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chore: Add trace spans for query-frontend #4620

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62 changes: 56 additions & 6 deletions pkg/frontend/readpath/queryfrontend/query_frontend.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,9 @@ import (

"github.com/go-kit/log"
"github.com/grafana/dskit/tenant"
"github.com/opentracing/opentracing-go"
"github.com/opentracing/opentracing-go/ext"
otlog "github.com/opentracing/opentracing-go/log"
"github.com/prometheus/prometheus/model/labels"
"github.com/prometheus/prometheus/promql/parser"
"google.golang.org/grpc/codes"
Expand Down Expand Up @@ -73,18 +76,26 @@ func (q *QueryFrontend) Query(
ctx context.Context,
req *queryv1.QueryRequest,
) (*queryv1.QueryResponse, error) {
span, ctx := opentracing.StartSpanFromContext(ctx, "QueryFrontend.Query")
defer span.Finish()
span.SetTag("start_time", req.StartTime)
span.SetTag("end_time", req.EndTime)
span.SetTag("label_selector", req.LabelSelector)

// This method is supposed to be the entry point of the read path
// in the future versions. Therefore, validation, overrides, and
// rest of the request handling should be moved here.
tenants, err := tenant.TenantIDs(ctx)
if err != nil {
return nil, status.Error(codes.InvalidArgument, err.Error())
}
span.SetTag("tenant_ids", tenants)

blocks, err := q.QueryMetadata(ctx, req)
if err != nil {
return nil, err
}
span.SetTag("block_count", len(blocks))
if len(blocks) == 0 {
return new(queryv1.QueryResponse), nil
}
Expand All @@ -98,7 +109,8 @@ func (q *QueryFrontend) Query(
p := queryplan.Build(blocks, 4, 20)

// Only check for symbolization if all tenants have it enabled
shouldSymbolize := q.shouldSymbolize(tenants, blocks)
shouldSymbolize := q.shouldSymbolize(ctx, tenants, blocks)
span.SetTag("should_symbolize", shouldSymbolize)

modifiedQueries := make([]*queryv1.Query, len(req.Query))
for i, originalQuery := range req.Query {
Expand Down Expand Up @@ -148,15 +160,29 @@ func (q *QueryFrontend) Query(
func (q *QueryFrontend) QueryMetadata(
ctx context.Context,
req *queryv1.QueryRequest,
) ([]*metastorev1.BlockMeta, error) {
) (blocks []*metastorev1.BlockMeta, err error) {
span, ctx := opentracing.StartSpanFromContext(ctx, "QueryFrontend.QueryMetadata")
defer func() {
if err != nil {
ext.LogError(span, err)
}
span.Finish()
}()
span.SetTag("start_time", req.StartTime)
span.SetTag("end_time", req.EndTime)
span.SetTag("label_selector", req.LabelSelector)

tenants, err := tenant.TenantIDs(ctx)
if err != nil {
return nil, status.Error(codes.InvalidArgument, err.Error())
}
span.SetTag("tenant_ids", tenants)

matchers, err := parser.ParseMetricSelector(req.LabelSelector)
if err != nil {
return nil, status.Error(codes.InvalidArgument, err.Error())
}

query := &metastorev1.QueryMetadataRequest{
TenantId: tenants,
StartTime: req.StartTime,
Expand Down Expand Up @@ -187,6 +213,7 @@ func (q *QueryFrontend) QueryMetadata(
if err != nil {
return nil, err
}
span.SetTag("blocks_count", len(md.Blocks))

return md.Blocks, nil
}
Expand All @@ -202,7 +229,12 @@ func (q *QueryFrontend) hasUnsymbolizedProfiles(block *metastorev1.BlockMeta) bo
}

// shouldSymbolize determines if we should symbolize profiles based on tenant settings
func (q *QueryFrontend) shouldSymbolize(tenants []string, blocks []*metastorev1.BlockMeta) bool {
func (q *QueryFrontend) shouldSymbolize(ctx context.Context, tenants []string, blocks []*metastorev1.BlockMeta) bool {
span := opentracing.SpanFromContext(ctx)
if span != nil {
span.LogFields(otlog.String("event", "shouldSymbolize"))
}

if q.symbolizer == nil {
return false
}
Expand All @@ -213,21 +245,39 @@ func (q *QueryFrontend) shouldSymbolize(tenants []string, blocks []*metastorev1.
}
}

blocksWithUnsymbolized := 0
for _, block := range blocks {
if q.hasUnsymbolizedProfiles(block) {
return true
blocksWithUnsymbolized++
}
}

return false
if span != nil {
span.LogFields(
otlog.Int("blocks_with_unsymbolized", blocksWithUnsymbolized),
otlog.Int("total_blocks", len(blocks)),
)
}

return blocksWithUnsymbolized > 0
}

// processAndSymbolizeProfiles handles the symbolization of profiles from the response
func (q *QueryFrontend) processAndSymbolizeProfiles(
ctx context.Context,
resp *queryv1.InvokeResponse,
originalQueries []*queryv1.Query,
) error {
) (err error) {
span, ctx := opentracing.StartSpanFromContext(ctx, "QueryFrontend.processAndSymbolizeProfiles")
defer func() {
if err != nil {
ext.LogError(span, err)
}
span.Finish()
}()
span.SetTag("query_count", len(originalQueries))
span.SetTag("report_count", len(resp.Reports))

if len(originalQueries) != len(resp.Reports) {
return fmt.Errorf("query/report count mismatch: %d queries but %d reports",
len(originalQueries), len(resp.Reports))
Expand Down