Add resolver cache statistics metrics

bind/bind.go

@@ -63,6 +63,7 @@ type View struct {
 	Cache           []Gauge
 	ResolverStats   []Counter
 	ResolverQueries []Counter
+	CacheStats      []Counter
 }
 
 // View represents statistics for a single BIND zone view.

bind/json/json.go

@@ -47,9 +47,10 @@ type Statistics struct {
 	ZoneStats  Counters  `json:"zonestats"`
 	Views      map[string]struct {
 		Resolver struct {
-			Cache  Gauges   `json:"cache"`
-			Qtypes Counters `json:"qtypes"`
-			Stats  Counters `json:"stats"`
+			Cache      Gauges   `json:"cache"`
+			Qtypes     Counters `json:"qtypes"`
+			Stats      Counters `json:"stats"`
+			CacheStats Counters `json:"cachestats"`
 		} `json:"resolver"`
 	} `json:"views"`
 }
@@ -156,6 +157,9 @@ func (c *Client) Stats(groups ...bind.StatisticGroup) (bind.Statistics, error) {
 			for k, val := range view.Resolver.Stats {
 				v.ResolverStats = append(v.ResolverStats, bind.Counter{Name: k, Counter: val})
 			}
+			for k, val := range view.Resolver.CacheStats {
+				v.CacheStats = append(v.CacheStats, bind.Counter{Name: k, Counter: val})
+			}
 			s.Views = append(s.Views, v)
 		}
 	}

bind/xml/xml.go

@@ -34,13 +34,14 @@ const (
 	// ZonesPath is the HTTP path of the v3 zones resource.
 	ZonesPath = "/xml/v3/zones"
 
-	nsstat   = "nsstat"
-	opcode   = "opcode"
-	qtype    = "qtype"
-	resqtype = "resqtype"
-	resstats = "resstats"
-	zonestat = "zonestat"
-	rcode    = "rcode"
+	nsstat     = "nsstat"
+	opcode     = "opcode"
+	qtype      = "qtype"
+	resqtype   = "resqtype"
+	resstats   = "resstats"
+	zonestat   = "zonestat"
+	rcode      = "rcode"
+	cachestats = "cachestats"
 )
 
 type Statistics struct {
@@ -170,6 +171,8 @@ func (c *Client) Stats(groups ...bind.StatisticGroup) (bind.Statistics, error) {
 					v.ResolverQueries = c.Counters
 				case resstats:
 					v.ResolverStats = c.Counters
+				case cachestats:
+					v.CacheStats = c.Counters
 				}
 			}
 			s.Views = append(s.Views, v)

bind_exporter.go

@@ -82,6 +82,11 @@ var (
 		"Number of outgoing DNS queries.",
 		[]string{"view", "type"}, nil,
 	)
+	cacheStats = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, resolver, "cache_stats"),
+		"Resolver cache statistics.",
+		[]string{"view", "type"}, nil,
+	)
 	resolverQueryDuration = prometheus.NewDesc(
 		prometheus.BuildFQName(namespace, resolver, "query_duration_seconds"),
 		"Resolver query round-trip time in seconds.",
@@ -333,6 +338,11 @@ func (c *viewCollector) Collect(ch chan<- prometheus.Metric) {
 				resolverQueries, prometheus.CounterValue, float64(s.Counter), v.Name, s.Name,
 			)
 		}
+		for _, s := range v.CacheStats {
+			ch <- prometheus.MustNewConstMetric(
+				cacheStats, prometheus.CounterValue, float64(s.Counter), v.Name, s.Name,
+			)
+		}
 		for _, s := range v.ResolverStats {
 			if desc, ok := resolverMetricStats[s.Name]; ok {
 				ch <- prometheus.MustNewConstMetric(