Enable Prometheus native histograms (#6524)

Add a NativeHistogramBucketFactor parameter to the use of
`NewHistogramVec` in order to enable use of Prometheus Native
Histograms.

This will store automatically computed sparse buckets in CoreDNS.
If a compatible Prometeus requests native histograms this data will
returned instead of the static buckets.

The default factor of 1.05 should provide high quality resolution data.

Signed-off-by: SuperQ <superq@gmail.com>

plugin/grpc/metrics.go

@@ -26,6 +26,7 @@ var (
 		Subsystem:                   "grpc",
 		Name:                        "request_duration_seconds",
 		Buckets:                     plugin.TimeBuckets,
+		NativeHistogramBucketFactor: plugin.NativeHistogramBucketFactor,
 		Help:                        "Histogram of the time each request took.",
 	}, []string{"to"})
 )

plugin/health/overloaded.go

@@ -71,6 +71,7 @@ var (
 		Subsystem:                   "health",
 		Name:                        "request_duration_seconds",
 		Buckets:                     plugin.SlimTimeBuckets,
+		NativeHistogramBucketFactor: plugin.NativeHistogramBucketFactor,
 		Help:                        "Histogram of the time (in seconds) each request took.",
 	})
 	// HealthFailures is the metric used to count how many times the health request failed

plugin/kubernetes/metrics.go

@@ -21,6 +21,7 @@ var (
 			Name:                        "rest_client_request_duration_seconds",
 			Help:                        "Request latency in seconds. Broken down by verb and host.",
 			Buckets:                     prometheus.DefBuckets,
+			NativeHistogramBucketFactor: plugin.NativeHistogramBucketFactor,
 		},
 		[]string{"verb", "host"},
 	)
@@ -33,6 +34,7 @@ var (
 			Name:                        "rest_client_rate_limiter_duration_seconds",
 			Help:                        "Client side rate limiter latency in seconds. Broken down by verb and host.",
 			Buckets:                     prometheus.DefBuckets,
+			NativeHistogramBucketFactor: plugin.NativeHistogramBucketFactor,
 		},
 		[]string{"verb", "host"},
 	)

plugin/kubernetes/object/metrics.go

@@ -30,6 +30,7 @@ var (
 		Name:      "dns_programming_duration_seconds",
 		// From 1 millisecond to ~17 minutes.
 		Buckets:                     prometheus.ExponentialBuckets(0.001, 2, 20),
+		NativeHistogramBucketFactor: plugin.NativeHistogramBucketFactor,
 		Help:                        "Histogram of the time (in seconds) it took to program a dns instance.",
 	}, []string{"service_kind"})
 

plugin/metrics/vars/vars.go

@@ -21,6 +21,7 @@ var (
 		Subsystem:                   subsystem,
 		Name:                        "request_duration_seconds",
 		Buckets:                     plugin.TimeBuckets,
+		NativeHistogramBucketFactor: plugin.NativeHistogramBucketFactor,
 		Help:                        "Histogram of the time (in seconds) each request took per zone.",
 	}, []string{"server", "zone", "view"})
 
@@ -30,6 +31,7 @@ var (
 		Name:                        "request_size_bytes",
 		Help:                        "Size of the EDNS0 UDP buffer in bytes (64K for TCP) per zone and protocol.",
 		Buckets:                     []float64{0, 100, 200, 300, 400, 511, 1023, 2047, 4095, 8291, 16e3, 32e3, 48e3, 64e3},
+		NativeHistogramBucketFactor: plugin.NativeHistogramBucketFactor,
 	}, []string{"server", "zone", "view", "proto"})
 
 	RequestDo = promauto.NewCounterVec(prometheus.CounterOpts{
@@ -45,6 +47,7 @@ var (
 		Name:                        "response_size_bytes",
 		Help:                        "Size of the returned response in bytes.",
 		Buckets:                     []float64{0, 100, 200, 300, 400, 511, 1023, 2047, 4095, 8291, 16e3, 32e3, 48e3, 64e3},
+		NativeHistogramBucketFactor: plugin.NativeHistogramBucketFactor,
 	}, []string{"server", "zone", "view", "proto"})
 
 	ResponseRcode = promauto.NewCounterVec(prometheus.CounterOpts{

plugin/pkg/proxy/metrics.go

@@ -14,6 +14,7 @@ var (
 		Subsystem:                   "proxy",
 		Name:                        "request_duration_seconds",
 		Buckets:                     plugin.TimeBuckets,
+		NativeHistogramBucketFactor: plugin.NativeHistogramBucketFactor,
 		Help:                        "Histogram of the time each request took.",
 	}, []string{"proxy_name", "to", "rcode"})
 

plugin/plugin.go

@@ -108,5 +108,9 @@ var TimeBuckets = prometheus.ExponentialBuckets(0.00025, 2, 16) // from 0.25ms t
 // SlimTimeBuckets is low cardinality set of duration buckets.
 var SlimTimeBuckets = prometheus.ExponentialBuckets(0.00025, 10, 5) // from 0.25ms to 2.5 seconds
 
+// NativeHistogramBucketFactor controls the resolution of Prometheus native histogram buckets.
+// See: https://pkg.go.dev/github.com/prometheus/client_golang@v1.19.0/prometheus#section-readme
+var NativeHistogramBucketFactor = 1.05
+
 // ErrOnce is returned when a plugin doesn't support multiple setups per server.
 var ErrOnce = errors.New("this plugin can only be used once per Server Block")