Add percentiles to the ping plugin (#7345)

plugins/inputs/ping/README.md

@@ -57,6 +57,9 @@ native Go by the Telegraf process, eliminating the need to execute the system
   ## option of the ping command.
   # interface = ""
 
+  ## Percentiles to calculate. This only works with the native method.
+  # percentiles = [50, 95, 99]
+
   ## Specify the ping executable binary.
   # binary = "ping"
 
@@ -147,10 +150,11 @@ sockets and the `ping_group_range` setting.
     - packets_received (integer)
     - percent_packet_loss (float)
     - ttl (integer, Not available on Windows)
-    - average_response_ms (integer)
-    - minimum_response_ms (integer)
-    - maximum_response_ms (integer)
-    - standard_deviation_ms (integer, Available on Windows only with native ping)
+    - average_response_ms (float)
+    - minimum_response_ms (float)
+    - maximum_response_ms (float)
+    - standard_deviation_ms (float, Available on Windows only with method = "native")
+    - percentile\<N\>_ms (float, Where `<N>` is the percentile specified in `percentiles`. Available with method = "native" only)
     - errors (float, Windows only)
     - reply_received (integer, Windows with method = "exec" only)
     - percent_reply_loss (float, Windows with method = "exec" only)

plugins/inputs/ping/ping.go

@@ -3,11 +3,13 @@ package ping
 import (
 	"context"
 	"errors"
+	"fmt"
 	"log"
 	"math"
 	"net"
 	"os/exec"
 	"runtime"
+	"sort"
 	"strings"
 	"sync"
 	"time"
@@ -69,6 +71,9 @@ type Ping struct {
 
 	// listenAddr is the address associated with the interface defined.
 	listenAddr string
+
+	// Calculate the given percentiles when using native method
+	Percentiles []int
 }
 
 func (*Ping) Description() string {
@@ -108,6 +113,9 @@ const sampleConfig = `
   ## option of the ping command.
   # interface = ""
 
+  ## Percentiles to calculate. This only works with the native method.
+  # percentiles = [50, 95, 99]
+
   ## Specify the ping executable binary.
   # binary = "ping"
 
@@ -345,11 +353,41 @@ finish:
 		log.Printf("D! [inputs.ping] %s", doErr.Error())
 	}
 
-	tags, fields := onFin(packetsSent, rsps, doErr, destination)
+	tags, fields := onFin(packetsSent, rsps, doErr, destination, p.Percentiles)
 	acc.AddFields("ping", fields, tags)
 }
 
-func onFin(packetsSent int, resps []*ping.Response, err error, destination string) (map[string]string, map[string]interface{}) {
+type durationSlice []time.Duration
+
+func (p durationSlice) Len() int           { return len(p) }
+func (p durationSlice) Less(i, j int) bool { return p[i] < p[j] }
+func (p durationSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
+// R7 from Hyndman and Fan (1996), which matches Excel
+func percentile(values durationSlice, perc int) time.Duration {
+	if perc < 0 {
+		perc = 0
+	}
+	if perc > 100 {
+		perc = 100
+	}
+	var percFloat = float64(perc) / 100.0
+
+	var count = len(values)
+	var rank = percFloat * float64(count-1)
+	var rankInteger = int(rank)
+	var rankFraction = rank - math.Floor(rank)
+
+	if rankInteger >= count-1 {
+		return values[count-1]
+	} else {
+		upper := values[rankInteger+1]
+		lower := values[rankInteger]
+		return lower + time.Duration(rankFraction*float64(upper-lower))
+	}
+}
+
+func onFin(packetsSent int, resps []*ping.Response, err error, destination string, percentiles []int) (map[string]string, map[string]interface{}) {
 	packetsRcvd := len(resps)
 
 	tags := map[string]string{"url": destination}
@@ -378,17 +416,35 @@ func onFin(packetsSent int, resps []*ping.Response, err error, destination strin
 	ttl := resps[0].TTL
 
 	var min, max, avg, total time.Duration
-	min = resps[0].RTT
-	max = resps[0].RTT
 
-	for _, res := range resps {
-		if res.RTT < min {
-			min = res.RTT
+	if len(percentiles) > 0 {
+		var rtt []time.Duration
+		for _, resp := range resps {
+			rtt = append(rtt, resp.RTT)
+			total += resp.RTT
+		}
+		sort.Sort(durationSlice(rtt))
+		min = rtt[0]
+		max = rtt[len(rtt)-1]
+
+		for _, perc := range percentiles {
+			var value = percentile(durationSlice(rtt), perc)
+			var field = fmt.Sprintf("percentile%v_ms", perc)
+			fields[field] = float64(value.Nanoseconds()) / float64(time.Millisecond)
 		}
-		if res.RTT > max {
-			max = res.RTT
+	} else {
+		min = resps[0].RTT
+		max = resps[0].RTT
+
+		for _, res := range resps {
+			if res.RTT < min {
+				min = res.RTT
+			}
+			if res.RTT > max {
+				max = res.RTT
+			}
+			total += res.RTT
 		}
-		total += res.RTT
 	}
 
 	avg = total / time.Duration(packetsRcvd)
@@ -433,6 +489,7 @@ func init() {
 			Method:       "exec",
 			Binary:       "ping",
 			Arguments:    []string{},
+			Percentiles:  []int{},
 		}
 	})
 }

plugins/inputs/ping/ping_test.go

@@ -413,11 +413,15 @@ func TestPingGatherNative(t *testing.T) {
 		Method:      "native",
 		Count:       5,
 		resolveHost: mockHostResolver,
+		Percentiles: []int{50, 95, 99},
 	}
 
 	assert.NoError(t, acc.GatherError(p.Gather))
 	assert.True(t, acc.HasPoint("ping", map[string]string{"url": "localhost"}, "packets_transmitted", 5))
 	assert.True(t, acc.HasPoint("ping", map[string]string{"url": "localhost"}, "packets_received", 5))
+	assert.True(t, acc.HasField("ping", "percentile50_ms"))
+	assert.True(t, acc.HasField("ping", "percentile95_ms"))
+	assert.True(t, acc.HasField("ping", "percentile99_ms"))
 }
 
 func mockHostResolverError(ctx context.Context, ipv6 bool, host string) (*net.IPAddr, error) {