chore(dataobj): use LRU cache for parsing labels (#15792)

pkg/dataobj/dataobj.go

@@ -11,6 +11,7 @@ import (
 	"fmt"
 
 	"github.com/grafana/dskit/flagext"
+	lru "github.com/hashicorp/golang-lru/v2"
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/thanos-io/objstore"
 
@@ -88,6 +89,8 @@ type Builder struct {
 	bucket   objstore.Bucket
 	tenantID string
 
+	labelCache *lru.Cache[string, labels.Labels]
+
 	dirty bool // Whether the builder has been modified since the last flush.
 
 	streams *streams.Streams
@@ -103,11 +106,18 @@ func NewBuilder(cfg BuilderConfig, bucket objstore.Bucket, tenantID string) (*Bu
 		return nil, err
 	}
 
+	labelCache, err := lru.New[string, labels.Labels](5000)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create LRU cache: %w", err)
+	}
+
 	return &Builder{
 		cfg:      cfg,
 		bucket:   bucket,
 		tenantID: tenantID,
 
+		labelCache: labelCache,
+
 		streams: streams.New(int(cfg.TargetPageSize)),
 		logs:    logs.New(int(cfg.TargetPageSize)),
 	}, nil
@@ -120,7 +130,7 @@ func NewBuilder(cfg BuilderConfig, bucket objstore.Bucket, tenantID string) (*Bu
 // Once a Builder is full, call [Builder.Flush] to flush the buffered data,
 // then call Append again with the same entry.
 func (b *Builder) Append(stream logproto.Stream) error {
-	ls, err := syntax.ParseLabels(stream.Labels)
+	ls, err := b.parseLabels(stream.Labels)
 	if err != nil {
 		return err
 	}
@@ -146,6 +156,20 @@ func (b *Builder) Append(stream logproto.Stream) error {
 	return nil
 }
 
+func (b *Builder) parseLabels(labelString string) (labels.Labels, error) {
+	labels, ok := b.labelCache.Get(labelString)
+	if ok {
+		return labels, nil
+	}
+
+	labels, err := syntax.ParseLabels(labelString)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse labels: %w", err)
+	}
+	b.labelCache.Add(labelString, labels)
+	return labels, nil
+}
+
 func (b *Builder) estimatedSize() int {
 	var size int
 	size += b.streams.EstimatedSize()