Alerting: Improve performance of tupleLablesToLabels function (#88736)

* Alerting: Improve performance of tupleLablesToLabels function

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>

* use %s for string rather than %v

Co-authored-by: Sofia Papagiannaki <1632407+papagian@users.noreply.github.com>

---------

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>
Co-authored-by: Sofia Papagiannaki <1632407+papagian@users.noreply.github.com>

pkg/services/ngalert/models/instance_labels.go

@@ -100,12 +100,16 @@ func tupleLablesToLabels(tuples tupleLabels) (InstanceLabels, error) {
 	if tuples == nil {
 		return InstanceLabels{}, nil
 	}
-	labels := make(map[string]string)
+
+	labels := make(map[string]string, len(tuples))
 	for _, tuple := range tuples {
-		if key, ok := labels[tuple[0]]; ok {
-			return nil, fmt.Errorf("duplicate key '%v' in lables: %v", key, tuples)
+		key, value := tuple[0], tuple[1]
+		if _, ok := labels[key]; ok {
+			return nil, fmt.Errorf("duplicate key '%s' in labels: %v", key, tuples)
 		}
-		labels[tuple[0]] = tuple[1]
+
+		labels[key] = value
 	}
+
 	return labels, nil
 }

pkg/services/ngalert/models/instance_labels_test.go

@@ -0,0 +1,114 @@
+package models
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestTupleLabelsToLabels(t *testing.T) {
+	t.Run("converts tupleLabels to InstanceLabels", func(t *testing.T) {
+		in := tupleLabels{
+			{"foo", "bar"},
+			{"baz", "qux"},
+		}
+
+		labels, err := tupleLablesToLabels(in)
+		require.NoError(t, err)
+		require.Equal(t, InstanceLabels{
+			"foo": "bar",
+			"baz": "qux",
+		}, labels)
+	})
+
+	t.Run("nil input gives empty output", func(t *testing.T) {
+		labels, err := tupleLablesToLabels(nil)
+		require.NoError(t, err)
+		require.Empty(t, labels)
+	})
+
+	t.Run("duplicate keys are not allowed", func(t *testing.T) {
+		in := tupleLabels{
+			{"foo", "bar"},
+			{"foo", "qux"},
+		}
+
+		_, err := tupleLablesToLabels(in)
+		require.Error(t, err)
+	})
+}
+
+func BenchmarkTupleLabelsToLabels(b *testing.B) {
+	b.Run("10 labels", func(b *testing.B) {
+		in := make(tupleLabels, 0, 10)
+		for i := 0; i < 10; i++ {
+			key := fmt.Sprintf("key%d", i)
+			value := fmt.Sprintf("value%d", i)
+			in = append(in, tupleLabel{key, value})
+		}
+
+		b.ResetTimer()
+
+		for i := 0; i < b.N; i++ {
+			_, err := tupleLablesToLabels(in)
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+
+	b.Run("100 labels", func(b *testing.B) {
+		in := make(tupleLabels, 0, 100)
+		for i := 0; i < 100; i++ {
+			key := fmt.Sprintf("key%d", i)
+			value := fmt.Sprintf("value%d", i)
+			in = append(in, tupleLabel{key, value})
+		}
+
+		b.ResetTimer()
+
+		for i := 0; i < b.N; i++ {
+			_, err := tupleLablesToLabels(in)
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+
+	b.Run("10_000 labels", func(b *testing.B) {
+		in := make(tupleLabels, 0, 10_000)
+		for i := 0; i < 10_000; i++ {
+			key := fmt.Sprintf("key%d", i)
+			value := fmt.Sprintf("value%d", i)
+			in = append(in, tupleLabel{key, value})
+		}
+
+		b.ResetTimer()
+
+		for i := 0; i < b.N; i++ {
+			_, err := tupleLablesToLabels(in)
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+
+	b.Run("1_000_000 labels", func(b *testing.B) {
+		in := make(tupleLabels, 0, 1_000_000)
+		for i := 0; i < 1_000_000; i++ {
+			key := fmt.Sprintf("key%d", i)
+			value := fmt.Sprintf("value%d", i)
+			in = append(in, tupleLabel{key, value})
+		}
+
+		b.ResetTimer()
+
+		for i := 0; i < b.N; i++ {
+			_, err := tupleLablesToLabels(in)
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}