usm: kafka: Use intern.StringInterner instead of manual implementation

Prefer code reuse.
The package handles better the lifecycle of the shared strings.

pkg/network/encoding/marshal/usm_kafka.go

@@ -65,7 +65,7 @@ func (e *kafkaEncoder) encodeData(connectionData *USMConnectionData[kafka.Key, *
 				header.SetRequest_type(uint32(key.RequestAPIKey))
 				header.SetRequest_version(uint32(key.RequestVersion))
 			})
-			builder.SetTopic(key.TopicName)
+			builder.SetTopic(key.TopicName.Get())
 			for statusCode, requestStat := range stats.ErrorCodeToStat {
 				if requestStat.Count == 0 {
 					continue

pkg/network/protocols/kafka/debugging/debugging.go

@@ -61,7 +61,7 @@ func Kafka(stats map[kafka.Key]*kafka.RequestStats) []RequestSummary {
 			},
 
 			Operation: operationName,
-			TopicName: key.TopicName,
+			TopicName: key.TopicName.Get(),
 			ByStatus:  make(map[int8]Stats, len(requestStat.ErrorCodeToStat)),
 		}
 

pkg/network/protocols/kafka/statkeeper.go

@@ -11,6 +11,7 @@ import (
 	"sync"
 
 	"github.com/DataDog/datadog-agent/pkg/network/config"
+	"github.com/DataDog/datadog-agent/pkg/util/intern"
 	"github.com/DataDog/datadog-agent/pkg/util/log"
 )
 
@@ -23,7 +24,7 @@ type StatKeeper struct {
 
 	// topicNames stores interned versions of the all topics currently stored in
 	// the `StatKeeper`
-	topicNames map[string]string
+	topicNames *intern.StringInterner
 }
 
 // NewStatkeeper creates a new StatKeeper
@@ -32,7 +33,7 @@ func NewStatkeeper(c *config.Config, telemetry *Telemetry) *StatKeeper {
 		stats:      make(map[Key]*RequestStats),
 		maxEntries: c.MaxKafkaStatsBuffered,
 		telemetry:  telemetry,
-		topicNames: make(map[string]string),
+		topicNames: intern.NewStringInterner(),
 	}
 }
 
@@ -73,26 +74,16 @@ func (statKeeper *StatKeeper) GetAndResetAllStats() map[Key]*RequestStats {
 	defer statKeeper.statsMutex.RUnlock()
 	ret := statKeeper.stats // No deep copy needed since `statKeeper.stats` gets reset
 	statKeeper.stats = make(map[Key]*RequestStats)
-	statKeeper.topicNames = make(map[string]string)
 	return ret
 }
 
-func (statKeeper *StatKeeper) extractTopicName(tx *KafkaTransaction) string {
+func (statKeeper *StatKeeper) extractTopicName(tx *KafkaTransaction) *intern.StringValue {
 	// Limit tx.Topic_name_size to not exceed the actual length of tx.Topic_name
 	if uint16(tx.Topic_name_size) > uint16(len(tx.Topic_name)) {
 		log.Debugf("Topic name size was changed from %d, to size: %d", tx.Topic_name_size, len(tx.Topic_name))
 		tx.Topic_name_size = uint8(len(tx.Topic_name))
 	}
 	b := tx.Topic_name[:tx.Topic_name_size]
 
-	// the trick here is that the Go runtime doesn't allocate the string used in
-	// the map lookup, so if we have seen this topic name before, we don't
-	// perform any allocations
-	if v, ok := statKeeper.topicNames[string(b)]; ok {
-		return v
-	}
-
-	v := string(b)
-	statKeeper.topicNames[v] = v
-	return v
+	return statKeeper.topicNames.Get(b)
 }

pkg/network/protocols/kafka/statkeeper_test.go

@@ -19,6 +19,7 @@ import (
 
 	"github.com/DataDog/datadog-agent/pkg/network/config"
 	"github.com/DataDog/datadog-agent/pkg/process/util"
+	"github.com/DataDog/datadog-agent/pkg/util/intern"
 )
 
 func BenchmarkStatKeeperSameTX(b *testing.B) {
@@ -66,10 +67,10 @@ func TestStatKeeper_extractTopicName(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			statKeeper := &StatKeeper{
-				topicNames: map[string]string{},
+				topicNames: intern.NewStringInterner(),
 			}
 			copy(tt.tx.Topic_name[:], strings.Repeat("*", len(tt.tx.Topic_name)))
-			if got := statKeeper.extractTopicName(tt.tx); len(got) != len(tt.want) {
+			if got := statKeeper.extractTopicName(tt.tx); len(got.Get()) != len(tt.want) {
 				t.Errorf("extractTopicName() = %v, want %v", got, tt.want)
 			}
 		})
@@ -105,7 +106,7 @@ func TestProcessKafkaTransactions(t *testing.T) {
 	assert.Equal(t, 0, len(sk.stats))
 	assert.Equal(t, numOfTopics, len(stats))
 	for key, stats := range stats {
-		assert.Equal(t, topicNamePrefix, key.TopicName[:len(topicNamePrefix)])
+		assert.Equal(t, topicNamePrefix, key.TopicName.Get()[:len(topicNamePrefix)])
 		for i := 0; i < 5; i++ {
 			s := stats.ErrorCodeToStat[int32(i)]
 			require.NotNil(t, s)

pkg/network/protocols/kafka/stats.go

@@ -7,7 +7,7 @@ package kafka
 
 import (
 	"github.com/DataDog/datadog-agent/pkg/network/types"
-	"github.com/DataDog/datadog-agent/pkg/process/util"
+	"github.com/DataDog/datadog-agent/pkg/util/intern"
 	"github.com/DataDog/datadog-agent/pkg/util/log"
 	"github.com/DataDog/sketches-go/ddsketch"
 )
@@ -29,20 +29,10 @@ const (
 type Key struct {
 	RequestAPIKey  uint16
 	RequestVersion uint16
-	TopicName      string
+	TopicName      *intern.StringValue
 	types.ConnectionKey
 }
 
-// NewKey generates a new Key
-func NewKey(saddr, daddr util.Address, sport, dport uint16, topicName string, requestAPIKey, requestAPIVersion uint16) Key {
-	return Key{
-		ConnectionKey:  types.NewConnectionKey(saddr, daddr, sport, dport),
-		TopicName:      topicName,
-		RequestAPIKey:  requestAPIKey,
-		RequestVersion: requestAPIVersion,
-	}
-}
-
 // RequestStats stores Kafka request statistics per Kafka error code
 // We include the error code here and not in the Key to avoid creating a new Key for each error code
 type RequestStats struct {

pkg/network/protocols/kafka/stats_testutil.go

@@ -0,0 +1,28 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2024-present Datadog, Inc.
+
+//go:build test
+
+package kafka
+
+import (
+	"github.com/DataDog/datadog-agent/pkg/network/types"
+	"github.com/DataDog/datadog-agent/pkg/process/util"
+	"github.com/DataDog/datadog-agent/pkg/util/intern"
+)
+
+var (
+	testInterner = intern.NewStringInterner()
+)
+
+// NewKey generates a new Key
+func NewKey(saddr, daddr util.Address, sport, dport uint16, topicName string, requestAPIKey, requestAPIVersion uint16) Key {
+	return Key{
+		ConnectionKey:  types.NewConnectionKey(saddr, daddr, sport, dport),
+		TopicName:      testInterner.GetString(topicName),
+		RequestAPIKey:  requestAPIKey,
+		RequestVersion: requestAPIVersion,
+	}
+}

pkg/network/usm/kafka_monitor_test.go

@@ -1616,7 +1616,7 @@ func validateProduceFetchCount(t *assert.CollectT, kafkaStats map[kafka.Key]*kaf
 		if hasTLSTag != validation.tlsEnabled {
 			continue
 		}
-		assert.Equal(t, topicName[:min(len(topicName), 80)], kafkaKey.TopicName)
+		assert.Equal(t, topicName[:min(len(topicName), 80)], kafkaKey.TopicName.Get())
 		assert.Greater(t, requestStats.FirstLatencySample, float64(1))
 		switch kafkaKey.RequestAPIKey {
 		case kafka.ProduceAPIKey:
@@ -1639,7 +1639,7 @@ func validateProduceFetchCountWithErrorCodes(t *assert.CollectT, kafkaStats map[
 	produceRequests := make(map[int32]int, len(validation.expectedNumberOfProduceRequests))
 	fetchRequests := make(map[int32]int, len(validation.expectedNumberOfFetchRequests))
 	for kafkaKey, kafkaStat := range kafkaStats {
-		assert.Equal(t, topicName[:min(len(topicName), 80)], kafkaKey.TopicName)
+		assert.Equal(t, topicName[:min(len(topicName), 80)], kafkaKey.TopicName.Get())
 		switch kafkaKey.RequestAPIKey {
 		case kafka.ProduceAPIKey:
 			assert.Equal(t, uint16(validation.expectedAPIVersionProduce), kafkaKey.RequestVersion)