feat: enable more linters and fix warnings (#364)

Signed-off-by: akartasov <agneum@gmail.com>

.golangci.yml

@@ -1,5 +1,28 @@
-# Run only staticcheck for now. Additional linters will be enabled one-by-one.
+run:
+  issues-exit-code: 1
+  tests: true
+  skip-dirs:
+    - vendor
 linters:
-  enable:
-  - staticcheck
   disable-all: true
+  enable:
+    - deadcode
+    - goimports
+    - gosimple
+    - govet
+    - ineffassign
+    - nakedret
+    - staticcheck
+    - structcheck
+    - unused
+    - varcheck
+    - whitespace
+linters-settings:
+  govet:
+    check-shadowing: true
+issues:
+  exclude-use-default: false
+  exclude:
+    - 'shadow: declaration of "err" shadows declaration at line (\d+)'
+  max-issues-per-linter: 0
+  max-same-issues: 0

main.go

@@ -45,11 +45,6 @@ import (
 	"github.com/prometheus/statsd_exporter/pkg/relay"
 )
 
-const (
-	defaultHelp = "Metric autogenerated by statsd_exporter."
-	regErrF     = "Failed to update metric"
-)
-
 var (
 	eventStats = promauto.NewCounterVec(
 		prometheus.CounterOpts{
@@ -171,17 +166,6 @@ var (
 	)
 )
 
-// uncheckedCollector wraps a Collector but its Describe method yields no Desc.
-// This allows incoming metrics to have inconsistent label sets
-type uncheckedCollector struct {
-	c prometheus.Collector
-}
-
-func (u uncheckedCollector) Describe(_ chan<- *prometheus.Desc) {}
-func (u uncheckedCollector) Collect(c chan<- prometheus.Metric) {
-	u.c.Collect(c)
-}
-
 func serveHTTP(mux http.Handler, listenAddress string, logger log.Logger) {
 	level.Error(logger).Log("msg", http.ListenAndServe(listenAddress, mux))
 	os.Exit(1)

pkg/exporter/exporter_test.go

@@ -74,12 +74,6 @@ var (
 			Help: "The number of lines discarded due to being too long.",
 		},
 	)
-	unixgramPackets = prometheus.NewCounter(
-		prometheus.CounterOpts{
-			Name: "statsd_exporter_unixgram_packets_total",
-			Help: "The total number of StatsD packets received over Unixgram.",
-		},
-	)
 	linesReceived = prometheus.NewCounter(
 		prometheus.CounterOpts{
 			Name: "statsd_exporter_lines_total",
@@ -111,17 +105,6 @@ var (
 			Help: "The number of errors parsing DogStatsD tags.",
 		},
 	)
-	configLoads = prometheus.NewCounterVec(
-		prometheus.CounterOpts{
-			Name: "statsd_exporter_config_reloads_total",
-			Help: "The number of configuration reloads.",
-		},
-		[]string{"outcome"},
-	)
-	mappingsCount = prometheus.NewGauge(prometheus.GaugeOpts{
-		Name: "statsd_exporter_loaded_mappings",
-		Help: "The current number of configured metric mappings.",
-	})
 	conflictingEventStats = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
 			Name: "statsd_exporter_events_conflict_total",

pkg/line/line.go

@@ -239,7 +239,6 @@ samples:
 	for _, sample := range samples {
 		samplesReceived.Inc()
 		components := strings.Split(sample, "|")
-		samplingFactor := 1.0
 		if len(components) < 2 || len(components) > 4 {
 			sampleErrors.WithLabelValues("malformed_component").Inc()
 			level.Debug(logger).Log("msg", "Bad component", "line", line)
@@ -273,7 +272,7 @@ samples:
 				switch component[0] {
 				case '@':
 
-					samplingFactor, err = strconv.ParseFloat(component[1:], 64)
+					samplingFactor, err := strconv.ParseFloat(component[1:], 64)
 					if err != nil {
 						level.Debug(logger).Log("msg", "Invalid sampling factor", "component", component[1:], "line", line)
 						sampleErrors.WithLabelValues("invalid_sample_factor").Inc()

pkg/mapper/fsm/dump.go

@@ -43,6 +43,6 @@ func (f *FSM) DumpFSM(w io.Writer) {
 		idx++
 	}
 	// color for start state
-	w.Write([]byte(fmt.Sprintf("0 [color=\"#a94442\",fillcolor=\"#f2dede\"];\n")))
+	w.Write([]byte(fmt.Sprintln("0 [color=\"#a94442\",fillcolor=\"#f2dede\"];")))
 	w.Write([]byte("}"))
 }

pkg/mapper/mapper.go

@@ -22,7 +22,7 @@ import (
 
 	"github.com/go-kit/log"
 	"github.com/prometheus/client_golang/prometheus"
-	yaml "gopkg.in/yaml.v2"
+	"gopkg.in/yaml.v2"
 
 	"github.com/prometheus/statsd_exporter/pkg/level"
 	"github.com/prometheus/statsd_exporter/pkg/mapper/fsm"
@@ -381,7 +381,6 @@ func (m *MetricMapper) GetMapping(statsdMetric string, statsdMetricType MetricTy
 // make a shallow copy so that we do not overwrite name
 // as multiple names can be matched by same mapping
 func copyMetricMapping(in *MetricMapping) *MetricMapping {
-	var out MetricMapping
-	out = *in
+	out := *in
 	return &out
 }