remove need for nil checks around statsd metrics

main.go

@@ -72,7 +72,7 @@ type configuration struct {
 // with all signers and permissions configured
 type autographer struct {
 	db                   *database.Handler
-	stats                *statsd.Client
+	stats                statsd.ClientInterface
 	nonces               *lru.Cache
 	debug                bool
 	heartbeatConf        *heartbeatConfig
@@ -166,11 +166,9 @@ func run(conf configuration, listen string, debug bool) {
 		ag.initHSM(conf)
 	}
 
-	if conf.Statsd.Addr != "" {
-		err = ag.addStats(conf)
-		if err != nil {
-			log.Fatal(err)
-		}
+	err = ag.addStats(conf)
+	if err != nil {
+		log.Fatal(err)
 	}
 
 	err = ag.addSigners(conf.Signers)
@@ -292,6 +290,7 @@ func newAutographer(cachesize int) (a *autographer) {
 	a.authBackend = newInMemoryAuthBackend()
 	a.nonces, err = lru.New(cachesize)
 	a.exit = make(chan interface{})
+	a.stats = &statsd.NoOpClient{}
 	if err != nil {
 		log.Fatal(err)
 	}

main_test.go

@@ -40,11 +40,9 @@ func TestMain(m *testing.M) {
 	if err != nil {
 		log.Fatal(err)
 	}
-	if conf.Statsd.Addr != "" {
-		err = ag.addStats(conf)
-		if err != nil {
-			log.Fatal(err)
-		}
+	err = ag.addStats(conf)
+	if err != nil {
+		log.Fatal(err)
 	}
 	if conf.HawkTimestampValidity != "" {
 		ag.hawkMaxTimestampSkew, err = time.ParseDuration(conf.HawkTimestampValidity)

signer/signer.go

@@ -523,14 +523,11 @@ type StatsClient struct {
 	signerTags []string
 
 	// stats is the statsd client for reporting metrics
-	stats *statsd.Client
+	stats statsd.ClientInterface
 }
 
 // NewStatsClient makes a new stats client
-func NewStatsClient(signerConfig Configuration, stats *statsd.Client) (*StatsClient, error) {
-	if stats == nil {
-		return nil, fmt.Errorf("xpi: statsd client is nil. Could not create StatsClient for signer %s", signerConfig.ID)
-	}
+func NewStatsClient(signerConfig Configuration, stats statsd.ClientInterface) (*StatsClient, error) {
 	return &StatsClient{
 		stats: stats,
 		signerTags: []string{

signer/xpi/xpi_test.go

@@ -57,12 +57,7 @@ func TestSignFile(t *testing.T) {
 					StatsSampleRate:        10 * time.Second,
 				}
 
-				statsdClient, err := statsd.NewBuffered("localhost:8135", 1)
-				if err != nil {
-					t.Fatalf("passing testcase %d: Error constructing statsdClient: %v", i, err)
-				}
-				statsdClient.Namespace = "test_autograph_stats_ns"
-				signerStatsClient, err := signer.NewStatsClient(testcase, statsdClient)
+				signerStatsClient, err := signer.NewStatsClient(testcase, &statsd.NoOpClient{})
 				if err != nil {
 					t.Fatalf("passing testcase %d: Error constructing signer.StatsdClient: %v", i, err)
 				}

stats.go

@@ -18,8 +18,19 @@ func loadStatsd(conf configuration) (*statsd.Client, error) {
 	return statsdClient, nil
 }
 
-func (a *autographer) addStats(conf configuration) (err error) {
-	a.stats, err = loadStatsd(conf)
+func (a *autographer) addStats(conf configuration) error {
+	if conf.Statsd.Addr == "" {
+		// a.stats is set to a safe value in newAutographer, so we leave it
+		// alone and return.
+		log.Infof("Statsd left disabled as no `statsd.addr` was provided in config")
+		return nil
+	}
+
+	stats, err := loadStatsd(conf)
+	if err != nil {
+		return err
+	}
+	a.stats = stats
 	log.Infof("Statsd enabled at %s with namespace %s", conf.Statsd.Addr, conf.Statsd.Namespace)
-	return err
+	return nil
 }