[#150] Add dropped logs metric

Signed-off-by: Pavel Pogodaev <p.pogodaev@yadro.com>

metrics/metrics.go

@@ -10,15 +10,17 @@ import (
 )
 
 const (
-	namespace       = "frostfs_http_gw"
-	stateSubsystem  = "state"
-	poolSubsystem   = "pool"
-	serverSubsystem = "server"
+	namespace          = "frostfs_http_gw"
+	stateSubsystem     = "state"
+	poolSubsystem      = "pool"
+	serverSubsystem    = "server"
+	statisticSubsystem = "statistic"
 )
 
 const (
 	healthMetric      = "health"
 	versionInfoMetric = "version_info"
+	droppedLogs       = "dropped_logs"
 )
 
 const (
@@ -30,21 +32,19 @@ const (
 )
 
 const (
-	methodGetBalance       = "get_balance"
-	methodPutContainer     = "put_container"
-	methodGetContainer     = "get_container"
-	methodListContainer    = "list_container"
-	methodDeleteContainer  = "delete_container"
-	methodGetContainerEacl = "get_container_eacl"
-	methodSetContainerEacl = "set_container_eacl"
-	methodEndpointInfo     = "endpoint_info"
-	methodNetworkInfo      = "network_info"
-	methodPutObject        = "put_object"
-	methodDeleteObject     = "delete_object"
-	methodGetObject        = "get_object"
-	methodHeadObject       = "head_object"
-	methodRangeObject      = "range_object"
-	methodCreateSession    = "create_session"
+	methodGetBalance      = "get_balance"
+	methodPutContainer    = "put_container"
+	methodGetContainer    = "get_container"
+	methodListContainer   = "list_container"
+	methodDeleteContainer = "delete_container"
+	methodEndpointInfo    = "endpoint_info"
+	methodNetworkInfo     = "network_info"
+	methodPutObject       = "put_object"
+	methodDeleteObject    = "delete_object"
+	methodGetObject       = "get_object"
+	methodHeadObject      = "head_object"
+	methodRangeObject     = "range_object"
+	methodCreateSession   = "create_session"
 )
 
 // HealthStatus of the gate application.
@@ -69,6 +69,7 @@ type GateMetrics struct {
 	stateMetrics
 	poolMetricsCollector
 	serverMetrics
+	statisticMetrics
 }
 
 type stateMetrics struct {
@@ -76,6 +77,10 @@ type stateMetrics struct {
 	versionInfo *prometheus.GaugeVec
 }
 
+type statisticMetrics struct {
+	droppedLogs prometheus.Counter
+}
+
 type poolMetricsCollector struct {
 	scraper             StatisticScraper
 	overallErrors       prometheus.Gauge
@@ -96,10 +101,14 @@ func NewGateMetrics(p StatisticScraper) *GateMetrics {
 	serverMetric := newServerMetrics()
 	serverMetric.register()
 
+	statsMetric := newStatisticMetrics()
+	statsMetric.register()
+
 	return &GateMetrics{
 		stateMetrics:         *stateMetric,
 		poolMetricsCollector: *poolMetric,
 		serverMetrics:        *serverMetric,
+		statisticMetrics:     *statsMetric,
 	}
 }
 
@@ -107,6 +116,7 @@ func (g *GateMetrics) Unregister() {
 	g.stateMetrics.unregister()
 	prometheus.Unregister(&g.poolMetricsCollector)
 	g.serverMetrics.unregister()
+	g.statisticMetrics.unregister()
 }
 
 func newStateMetrics() *stateMetrics {
@@ -116,6 +126,20 @@ func newStateMetrics() *stateMetrics {
 	}
 }
 
+func newStatisticMetrics() *statisticMetrics {
+	return &statisticMetrics{
+		droppedLogs: mustNewCounter(appMetricsDesc[statisticSubsystem][droppedLogs]),
+	}
+}
+
+func (s *statisticMetrics) register() {
+	prometheus.MustRegister(s.droppedLogs)
+}
+
+func (s *statisticMetrics) unregister() {
+	prometheus.Unregister(s.droppedLogs)
+}
+
 func (m stateMetrics) register() {
 	prometheus.MustRegister(m.healthCheck)
 	prometheus.MustRegister(m.versionInfo)
@@ -134,6 +158,13 @@ func (m stateMetrics) SetVersion(ver string) {
 	m.versionInfo.WithLabelValues(ver).Set(1)
 }
 
+func (s *statisticMetrics) DroppedLogsInc() {
+	if s == nil {
+		return
+	}
+	s.droppedLogs.Inc()
+}
+
 func newPoolMetricsCollector(p StatisticScraper) *poolMetricsCollector {
 	return &poolMetricsCollector{
 		scraper:             p,