Adding mapping cache

README.md

@@ -348,6 +348,17 @@ mappings:
 
 Possible values for `match_metric_type` are `gauge`, `counter` and `timer`.
 
+### Mapping cache size and cache replacement polixy
+
+There is a cache used to improve the performance of the metric mapping, that can greatly improvement performance.
+The cache has a default maximum of 1000 unique statsd metric names -> prometheus metrics mappings that it can store.
+This maximum can be adjust using the `statsd.cache-size` flag.
+
+If the maximum is reached, entries are rotated using the [least recently used replacement policy](https://en.wikipedia.org/wiki/Cache_replacement_policies#Least_recently_used_(LRU)).
+
+If you are using this exporter to reduce the cardinality of your data, a high maximum cache size can be a costly use of memory.
+
+
 ### Time series expiration
 
 The `ttl` parameter can be used to define the expiration time for stale metrics.

exporter_test.go

@@ -55,7 +55,10 @@ func TestNegativeCounter(t *testing.T) {
 	errorCounter := errorEventStats.WithLabelValues("illegal_negative_counter")
 	prev := getTelemetryCounterValue(errorCounter)
 
-	ex := NewExporter(&mapper.MetricMapper{})
+	testMapper := mapper.MetricMapper{}
+	testMapper.InitCache(0)
+
+	ex := NewExporter(&testMapper)
 	ex.Listen(events)
 
 	updated := getTelemetryCounterValue(errorCounter)
@@ -131,7 +134,7 @@ mappings:
   name: "histogram_test"
 `
 	testMapper := &mapper.MetricMapper{}
-	err := testMapper.InitFromYAMLString(config)
+	err := testMapper.InitFromYAMLString(config, 0)
 	if err != nil {
 		t.Fatalf("Config load error: %s %s", config, err)
 	}
@@ -180,7 +183,7 @@ mappings:
   name: "${1}"
 `
 	testMapper := &mapper.MetricMapper{}
-	err := testMapper.InitFromYAMLString(config)
+	err := testMapper.InitFromYAMLString(config, 0)
 	if err != nil {
 		t.Fatalf("Config load error: %s %s", config, err)
 	}
@@ -218,15 +221,20 @@ func TestInvalidUtf8InDatadogTagValue(t *testing.T) {
 		close(events)
 	}()
 
-	ex := NewExporter(&mapper.MetricMapper{})
+	testMapper := mapper.MetricMapper{}
+	testMapper.InitCache(0)
+
+	ex := NewExporter(&testMapper)
 	ex.Listen(events)
 }
 
 func TestHistogramUnits(t *testing.T) {
 	// Start exporter with a synchronous channel
 	events := make(chan Events)
 	go func() {
-		ex := NewExporter(&mapper.MetricMapper{})
+		testMapper := mapper.MetricMapper{}
+		testMapper.InitCache(0)
+		ex := NewExporter(&testMapper)
 		ex.mapper.Defaults.TimerType = mapper.TimerTypeHistogram
 		ex.Listen(events)
 	}()
@@ -338,7 +346,7 @@ mappings:
 `
 	// Create mapper from config and start an Exporter with a synchronous channel
 	testMapper := &mapper.MetricMapper{}
-	err := testMapper.InitFromYAMLString(config)
+	err := testMapper.InitFromYAMLString(config, 0)
 	if err != nil {
 		t.Fatalf("Config load error: %s %s", config, err)
 	}

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc // indirect
 	github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/hashicorp/golang-lru v0.5.1
 	github.com/howeyc/fsnotify v0.0.0-20151003194602-f0c08ee9c607
 	github.com/kr/pretty v0.1.0 // indirect
 	github.com/mattn/go-isatty v0.0.4 // indirect

go.sum

@@ -16,6 +16,8 @@ github.com/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
 github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/hashicorp/golang-lru v0.5.1 h1:0hERBMJE1eitiLkihrMvRVBYAkpHzc/J3QdDN+dAcgU=
+github.com/hashicorp/golang-lru v0.5.1/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
 github.com/howeyc/fsnotify v0.0.0-20151003194602-f0c08ee9c607 h1:+7wvV++11s0Okyl1dekihkIiCIYDz+Qk2LvxAShINU4=
 github.com/howeyc/fsnotify v0.0.0-20151003194602-f0c08ee9c607/go.mod h1:41HzSPxBGeFRQKEEwgh49TRw/nKBsYZ2cF1OzPjSJsA=
 github.com/hpcloud/tail v1.0.0 h1:nfCOvKYfkgYP8hkirhJocXT2+zOD8yUNjXaWfTlyFKI=

main.go

@@ -91,7 +91,7 @@ func tcpAddrFromString(addr string) *net.TCPAddr {
 	}
 }
 
-func watchConfig(fileName string, mapper *mapper.MetricMapper) {
+func watchConfig(fileName string, mapper *mapper.MetricMapper, cacheSize int) {
 	watcher, err := fsnotify.NewWatcher()
 	if err != nil {
 		log.Fatal(err)
@@ -106,7 +106,7 @@ func watchConfig(fileName string, mapper *mapper.MetricMapper) {
 		select {
 		case ev := <-watcher.Event:
 			log.Infof("Config file changed (%s), attempting reload", ev)
-			err = mapper.InitFromFile(fileName)
+			err = mapper.InitFromFile(fileName, cacheSize)
 			if err != nil {
 				log.Errorln("Error reloading config:", err)
 				configLoads.WithLabelValues("failure").Inc()
@@ -149,6 +149,7 @@ func main() {
 		statsdUnixSocketMode = kingpin.Flag("statsd.unixsocket-mode", "The permission mode of the unix socket.").Default("755").String()
 		mappingConfig        = kingpin.Flag("statsd.mapping-config", "Metric mapping configuration file name.").String()
 		readBuffer           = kingpin.Flag("statsd.read-buffer", "Size (in bytes) of the operating system's transmit read buffer associated with the UDP or Unixgram connection. Please make sure the kernel parameters net.core.rmem_max is set to a value greater than the value specified.").Int()
+		cacheSize            = kingpin.Flag("statsd.cache-size", "Maximum size of your metric mapping cache. Relies on least recently used replacement policy if max size is reached.").Default("1000").Int()
 		dumpFSMPath          = kingpin.Flag("debug.dump-fsm", "The path to dump internal FSM generated for glob matching as Dot file.").Default("").String()
 	)
 
@@ -247,7 +248,7 @@ func main() {
 
 	mapper := &mapper.MetricMapper{MappingsCount: mappingsCount}
 	if *mappingConfig != "" {
-		err := mapper.InitFromFile(*mappingConfig)
+		err := mapper.InitFromFile(*mappingConfig, *cacheSize)
 		if err != nil {
 			log.Fatal("Error loading config:", err)
 		}
@@ -257,7 +258,9 @@ func main() {
 				log.Fatal("Error dumping FSM:", err)
 			}
 		}
-		go watchConfig(*mappingConfig, mapper)
+		go watchConfig(*mappingConfig, mapper, *cacheSize)
+	} else {
+		mapper.InitCache(*cacheSize)
 	}
 	exporter := NewExporter(mapper)
 

pkg/mapper/mapper.go

@@ -20,6 +20,7 @@ import (
 	"sync"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/common/log"
 	"github.com/prometheus/statsd_exporter/pkg/mapper/fsm"
 	yaml "gopkg.in/yaml.v2"
 	"time"
@@ -49,7 +50,8 @@ type MetricMapper struct {
 	FSM      *fsm.FSM
 	doFSM    bool
 	doRegex  bool
-	mutex    sync.Mutex
+	cache    MetricMapperCache
+	mutex    sync.RWMutex
 
 	MappingsCount prometheus.Gauge
 }
@@ -83,7 +85,7 @@ var defaultQuantiles = []metricObjective{
 	{Quantile: 0.99, Error: 0.001},
 }
 
-func (m *MetricMapper) InitFromYAMLString(fileContents string) error {
+func (m *MetricMapper) InitFromYAMLString(fileContents string, cacheSize int) error {
 	var n MetricMapper
 
 	if err := yaml.Unmarshal([]byte(fileContents), &n); err != nil {
@@ -189,6 +191,8 @@ func (m *MetricMapper) InitFromYAMLString(fileContents string) error {
 
 	m.Defaults = n.Defaults
 	m.Mappings = n.Mappings
+	m.InitCache(cacheSize)
+
 	if n.doFSM {
 		var mappings []string
 		for _, mapping := range n.Mappings {
@@ -206,19 +210,37 @@ func (m *MetricMapper) InitFromYAMLString(fileContents string) error {
 	if m.MappingsCount != nil {
 		m.MappingsCount.Set(float64(len(n.Mappings)))
 	}
-
 	return nil
 }
 
-func (m *MetricMapper) InitFromFile(fileName string) error {
+func (m *MetricMapper) InitFromFile(fileName string, cacheSize int) error {
 	mappingStr, err := ioutil.ReadFile(fileName)
 	if err != nil {
 		return err
 	}
-	return m.InitFromYAMLString(string(mappingStr))
+
+	return m.InitFromYAMLString(string(mappingStr), cacheSize)
+}
+
+func (m *MetricMapper) InitCache(cacheSize int) {
+	if cacheSize == 0 {
+		m.cache = NewMetricMapperNoopCache()
+	} else {
+		cache, err := NewMetricMapperCache(cacheSize)
+		if err != nil {
+			log.Fatalf("Unable to setup metric cache. Caused by: %s", err)
+		}
+		m.cache = cache
+	}
 }
 
 func (m *MetricMapper) GetMapping(statsdMetric string, statsdMetricType MetricType) (*MetricMapping, prometheus.Labels, bool) {
+	m.mutex.RLock()
+	defer m.mutex.RUnlock()
+	result, cached := m.cache.Get(statsdMetric)
+	if cached {
+		return result.Mapping, result.Labels, result.Matched
+	}
 	// glob matching
 	if m.doFSM {
 		finalState, captures := m.FSM.GetMapping(statsdMetric, string(statsdMetricType))
@@ -230,17 +252,18 @@ func (m *MetricMapper) GetMapping(statsdMetric string, statsdMetricType MetricTy
 			for index, formatter := range result.labelFormatters {
 				labels[result.labelKeys[index]] = formatter.Format(captures)
 			}
+
+			m.cache.AddMatch(statsdMetric, result, labels)
+
 			return result, labels, true
 		} else if !m.doRegex {
 			// if there's no regex match type, return immediately
+			m.cache.AddMiss(statsdMetric)
 			return nil, nil, false
 		}
 	}
 
 	// regex matching
-	m.mutex.Lock()
-	defer m.mutex.Unlock()
-
 	for _, mapping := range m.Mappings {
 		// if a rule don't have regex matching type, the regex field is unset
 		if mapping.regex == nil {
@@ -268,8 +291,11 @@ func (m *MetricMapper) GetMapping(statsdMetric string, statsdMetricType MetricTy
 			labels[label] = string(value)
 		}
 
+		m.cache.AddMatch(statsdMetric, &mapping, labels)
+
 		return &mapping, labels, true
 	}
 
+	m.cache.AddMiss(statsdMetric)
 	return nil, nil, false
 }