reporting rtt with the ping metric

engine/access/ping/engine.go

@@ -107,21 +107,18 @@ func (e *Engine) startPing() {
 // pingNode pings the given peer and updates the metrics with the result and the additional node information
 func (e *Engine) pingNode(peer *flow.Identity) {
 	id := peer.ID()
-	reachable := e.pingAddress(id)
-	info := e.nodeInfo[id]
-	e.metrics.NodeReachable(peer, info, reachable)
-}
 
-// pingAddress sends a ping request to the given address, and block until either receive
-// a ping respond then return true, or hitting a timeout and return false.
-// if there is other unknown error, return false
-func (e *Engine) pingAddress(target flow.Identifier) bool {
-	// ignore the ping duration for now
-	// ping will timeout in libp2p.PingTimeoutSecs seconds
-	_, err := e.middleware.Ping(target)
+	// ping the node
+	rtt, err := e.middleware.Ping(id) // ping will timeout in libp2p.PingTimeoutSecs seconds
 	if err != nil {
-		e.log.Debug().Err(err).Str("target", target.String()).Msg("failed to ping")
-		return false
+		e.log.Debug().Err(err).Str("target", id.String()).Msg("failed to ping")
+		// report the rtt duration as negative to make it easier to distinguish between pingable and non-pingable nodes
+		rtt = -1
 	}
-	return true
+
+	// get the additional info about the node
+	info := e.nodeInfo[id]
+
+	// update metric
+	e.metrics.NodeReachable(peer, info, rtt)
 }

module/metrics.go

@@ -328,7 +328,7 @@ type TransactionMetrics interface {
 }
 
 type PingMetrics interface {
-	// NodeReachable tracks the node availability of the node and reports it as 1 if the node was successfully pinged, 0
-	// otherwise. The nodeInfo provides additional information about the node such as the name of the node operator
-	NodeReachable(node *flow.Identity, nodeInfo string, reachable bool)
+	// NodeReachable tracks the round trip time in milliseconds taken to ping a node
+	// The nodeInfo provides additional information about the node such as the name of the node operator
+	NodeReachable(node *flow.Identity, nodeInfo string, rtt time.Duration)
 }

module/metrics/ping.go

@@ -1,6 +1,8 @@
 package metrics
 
 import (
+	"time"
+
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 
@@ -23,14 +25,17 @@ func NewPingCollector() *PingCollector {
 	return pc
 }
 
-func (pc *PingCollector) NodeReachable(node *flow.Identity, nodeInfo string, reachable bool) {
-	var val float64
-	if reachable {
-		val = 1
+func (pc *PingCollector) NodeReachable(node *flow.Identity, nodeInfo string, rtt time.Duration) {
+	var rttValue float64
+	if rtt > 0 {
+		rttValue = float64(rtt.Milliseconds())
+	} else {
+		rttValue = -1
 	}
+
 	pc.reachable.With(prometheus.Labels{
 		LabelNodeID:   node.String(),
 		LabelNodeRole: node.Role.String(),
 		LabelNodeInfo: nodeInfo}).
-		Set(val)
+		Set(rttValue)
 }