Remove unneeded locks in add_kubernetes_metadata (#16979)

Read/write mutexes in matchers and indexers are only locked for read,
making them unnecesary. These locks are acquired for any event that is
enriched by the processor, so unneeded locking may affect performance.

Also, refactor locking in indexing registry so it is used in all cases.

libbeat/processors/add_kubernetes_metadata/indexers.go

@@ -19,7 +19,6 @@ package add_kubernetes_metadata
 
 import (
 	"fmt"
-	"sync"
 
 	"github.com/elastic/beats/v7/libbeat/common/kubernetes/metadata"
 
@@ -55,7 +54,6 @@ type MetadataIndex struct {
 }
 
 type Indexers struct {
-	sync.RWMutex
 	indexers []Indexer
 }
 
@@ -91,8 +89,6 @@ func NewIndexers(configs PluginConfig, metaGen metadata.MetaGen) *Indexers {
 // GetIndexes returns the composed index list from all registered indexers
 func (i *Indexers) GetIndexes(pod *kubernetes.Pod) []string {
 	var indexes []string
-	i.RLock()
-	defer i.RUnlock()
 	for _, indexer := range i.indexers {
 		for _, i := range indexer.GetIndexes(pod) {
 			indexes = append(indexes, i)
@@ -104,8 +100,6 @@ func (i *Indexers) GetIndexes(pod *kubernetes.Pod) []string {
 // GetMetadata returns the composed metadata list from all registered indexers
 func (i *Indexers) GetMetadata(pod *kubernetes.Pod) []MetadataIndex {
 	var metadata []MetadataIndex
-	i.RLock()
-	defer i.RUnlock()
 	for _, indexer := range i.indexers {
 		for _, m := range indexer.GetMetadata(pod) {
 			metadata = append(metadata, m)
@@ -116,8 +110,6 @@ func (i *Indexers) GetMetadata(pod *kubernetes.Pod) []MetadataIndex {
 
 // Empty returns true if indexers list is empty
 func (i *Indexers) Empty() bool {
-	i.RLock()
-	defer i.RUnlock()
 	if len(i.indexers) == 0 {
 		return true
 	}

libbeat/processors/add_kubernetes_metadata/indexing.go

@@ -50,30 +50,36 @@ func NewRegister() *Register {
 
 // AddIndexer to the register
 func (r *Register) AddIndexer(name string, indexer IndexerConstructor) {
-	r.RWMutex.Lock()
-	defer r.RWMutex.Unlock()
+	r.Lock()
+	defer r.Unlock()
 	r.indexers[name] = indexer
 }
 
 // AddMatcher to the register
 func (r *Register) AddMatcher(name string, matcher MatcherConstructor) {
-	r.RWMutex.Lock()
-	defer r.RWMutex.Unlock()
+	r.Lock()
+	defer r.Unlock()
 	r.matchers[name] = matcher
 }
 
 // AddIndexer to the register
 func (r *Register) AddDefaultIndexerConfig(name string, config common.Config) {
+	r.Lock()
+	defer r.Unlock()
 	r.defaultIndexerConfigs[name] = config
 }
 
 // AddMatcher to the register
 func (r *Register) AddDefaultMatcherConfig(name string, config common.Config) {
+	r.Lock()
+	defer r.Unlock()
 	r.defaultMatcherConfigs[name] = config
 }
 
 // AddIndexer to the register
 func (r *Register) GetIndexer(name string) IndexerConstructor {
+	r.RLock()
+	defer r.RUnlock()
 	indexer, ok := r.indexers[name]
 	if ok {
 		return indexer
@@ -84,6 +90,8 @@ func (r *Register) GetIndexer(name string) IndexerConstructor {
 
 // AddMatcher to the register
 func (r *Register) GetMatcher(name string) MatcherConstructor {
+	r.RLock()
+	defer r.RUnlock()
 	matcher, ok := r.matchers[name]
 	if ok {
 		return matcher
@@ -92,10 +100,30 @@ func (r *Register) GetMatcher(name string) MatcherConstructor {
 	}
 }
 
-func (r *Register) GetDefaultIndexerConfigs() map[string]common.Config {
-	return r.defaultIndexerConfigs
+// GetDefaultIndexerConfigs obtains the plugin configuration for the default indexer
+// configurations registered
+func (r *Register) GetDefaultIndexerConfigs() PluginConfig {
+	r.RLock()
+	defer r.RUnlock()
+
+	configs := make(PluginConfig, 0, len(r.defaultIndexerConfigs))
+	for key, cfg := range r.defaultIndexerConfigs {
+		configs = append(configs, map[string]common.Config{key: cfg})
+	}
+
+	return configs
 }
 
-func (r *Register) GetDefaultMatcherConfigs() map[string]common.Config {
-	return r.defaultMatcherConfigs
+// GetDefaultMatcherConfigs obtains the plugin configuration for the default matcher
+// configurations registered
+func (r *Register) GetDefaultMatcherConfigs() PluginConfig {
+	r.RLock()
+	defer r.RUnlock()
+
+	configs := make(PluginConfig, 0, len(r.defaultMatcherConfigs))
+	for key, cfg := range r.defaultMatcherConfigs {
+		configs = append(configs, map[string]common.Config{key: cfg})
+	}
+
+	return configs
 }

libbeat/processors/add_kubernetes_metadata/kubernetes.go

@@ -100,20 +100,12 @@ func New(cfg *common.Config) (processors.Processor, error) {
 
 	//Load default indexer configs
 	if config.DefaultIndexers.Enabled == true {
-		Indexing.RLock()
-		for key, cfg := range Indexing.GetDefaultIndexerConfigs() {
-			config.Indexers = append(config.Indexers, map[string]common.Config{key: cfg})
-		}
-		Indexing.RUnlock()
+		config.Indexers = Indexing.GetDefaultIndexerConfigs()
 	}
 
 	//Load default matcher configs
 	if config.DefaultMatchers.Enabled == true {
-		Indexing.RLock()
-		for key, cfg := range Indexing.GetDefaultMatcherConfigs() {
-			config.Matchers = append(config.Matchers, map[string]common.Config{key: cfg})
-		}
-		Indexing.RUnlock()
+		config.Matchers = Indexing.GetDefaultMatcherConfigs()
 	}
 
 	processor := &kubernetesAnnotator{

libbeat/processors/add_kubernetes_metadata/matchers.go

@@ -19,7 +19,6 @@ package add_kubernetes_metadata
 
 import (
 	"fmt"
-	"sync"
 
 	"github.com/elastic/beats/v7/libbeat/beat"
 	"github.com/elastic/beats/v7/libbeat/common"
@@ -43,7 +42,6 @@ type Matcher interface {
 }
 
 type Matchers struct {
-	sync.RWMutex
 	matchers []Matcher
 }
 
@@ -76,8 +74,6 @@ func NewMatchers(configs PluginConfig) *Matchers {
 
 // MetadataIndex returns the index string for the first matcher from the Registry returning one
 func (m *Matchers) MetadataIndex(event common.MapStr) string {
-	m.RLock()
-	defer m.RUnlock()
 	for _, matcher := range m.matchers {
 		index := matcher.MetadataIndex(event)
 		if index != "" {
@@ -90,8 +86,6 @@ func (m *Matchers) MetadataIndex(event common.MapStr) string {
 }
 
 func (m *Matchers) Empty() bool {
-	m.RLock()
-	defer m.RUnlock()
 	if len(m.matchers) == 0 {
 		return true
 	}