cluster: add more metrics (#1941)

- alertmanager_cluster_alive_messages_total, total number of alive
messages received.
- alertmanager_cluster_peer_info, a constant metric labeled by peer name.
- alertmanager_cluster_pings_seconds, histogram of latencies for ping
messages.

Signed-off-by: Simon Pasquier <spasquie@redhat.com>

cluster/cluster.go

@@ -179,7 +179,7 @@ func Create(
 		knownPeers:    knownPeers,
 	}
 
-	p.register(reg)
+	p.register(reg, name.String())
 
 	retransmit := len(knownPeers) / 2
 	if retransmit < 3 {
@@ -192,6 +192,8 @@ func Create(
 	cfg.BindAddr = bindHost
 	cfg.BindPort = bindPort
 	cfg.Delegate = p.delegate
+	cfg.Ping = p.delegate
+	cfg.Alive = p.delegate
 	cfg.Events = p.delegate
 	cfg.GossipInterval = gossipInterval
 	cfg.PushPullInterval = pushPullInterval
@@ -304,7 +306,15 @@ func (l *logWriter) Write(b []byte) (int, error) {
 	return len(b), level.Debug(l.l).Log("memberlist", string(b))
 }
 
-func (p *Peer) register(reg prometheus.Registerer) {
+func (p *Peer) register(reg prometheus.Registerer, name string) {
+	peerInfo := prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Name:        "alertmanager_cluster_peer_info",
+			Help:        "A metric with a constant '1' value labeled by peer name.",
+			ConstLabels: prometheus.Labels{"peer": name},
+		},
+	)
+	peerInfo.Set(1)
 	clusterFailedPeers := prometheus.NewGaugeFunc(prometheus.GaugeOpts{
 		Name: "alertmanager_cluster_failed_peers",
 		Help: "Number indicating the current number of failed peers in the cluster.",
@@ -346,7 +356,7 @@ func (p *Peer) register(reg prometheus.Registerer) {
 		Help: "A counter of the number of peers that have joined.",
 	})
 
-	reg.MustRegister(clusterFailedPeers, p.failedReconnectionsCounter, p.reconnectionsCounter,
+	reg.MustRegister(peerInfo, clusterFailedPeers, p.failedReconnectionsCounter, p.reconnectionsCounter,
 		p.peerLeaveCounter, p.peerUpdateCounter, p.peerJoinCounter, p.refreshCounter, p.failedRefreshCounter)
 }
 

cluster/delegate.go

@@ -44,6 +44,8 @@ type delegate struct {
 	messagesSent         *prometheus.CounterVec
 	messagesSentSize     *prometheus.CounterVec
 	messagesPruned       prometheus.Counter
+	nodeAlive            *prometheus.CounterVec
+	nodePingDuration     *prometheus.HistogramVec
 }
 
 func newDelegate(l log.Logger, reg prometheus.Registerer, p *Peer, retransmit int) *delegate {
@@ -95,6 +97,17 @@ func newDelegate(l log.Logger, reg prometheus.Registerer, p *Peer, retransmit in
 	}, func() float64 {
 		return float64(bcast.NumQueued())
 	})
+	nodeAlive := prometheus.NewCounterVec(prometheus.CounterOpts{
+		Name: "alertmanager_cluster_alive_messages_total",
+		Help: "Total number of received alive messages.",
+	}, []string{"peer"},
+	)
+	nodePingDuration := prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Name:    "alertmanager_cluster_pings_seconds",
+		Help:    "Histogram of latencies for ping messages.",
+		Buckets: []float64{.005, .01, .025, .05, .1, .25, .5},
+	}, []string{"peer"},
+	)
 
 	messagesReceived.WithLabelValues(fullState)
 	messagesReceivedSize.WithLabelValues(fullState)
@@ -106,7 +119,9 @@ func newDelegate(l log.Logger, reg prometheus.Registerer, p *Peer, retransmit in
 	messagesSentSize.WithLabelValues(update)
 
 	reg.MustRegister(messagesReceived, messagesReceivedSize, messagesSent, messagesSentSize,
-		gossipClusterMembers, peerPosition, healthScore, messagesQueued, messagesPruned)
+		gossipClusterMembers, peerPosition, healthScore, messagesQueued, messagesPruned,
+		nodeAlive, nodePingDuration,
+	)
 
 	d := &delegate{
 		logger:               l,
@@ -117,6 +132,8 @@ func newDelegate(l log.Logger, reg prometheus.Registerer, p *Peer, retransmit in
 		messagesSent:         messagesSent,
 		messagesSentSize:     messagesSentSize,
 		messagesPruned:       messagesPruned,
+		nodeAlive:            nodeAlive,
+		nodePingDuration:     nodePingDuration,
 	}
 
 	go d.handleQueueDepth()
@@ -226,6 +243,22 @@ func (d *delegate) NotifyUpdate(n *memberlist.Node) {
 	d.Peer.peerUpdate(n)
 }
 
+// NotifyAlive implements the memberlist.AliveDelegate interface.
+func (d *delegate) NotifyAlive(peer *memberlist.Node) error {
+	d.nodeAlive.WithLabelValues(peer.Name).Inc()
+	return nil
+}
+
+// AckPayload implements the memberlist.PingDelegate interface.
+func (d *delegate) AckPayload() []byte {
+	return []byte{}
+}
+
+// NotifyPingComplete implements the memberlist.PingDelegate interface.
+func (d *delegate) NotifyPingComplete(peer *memberlist.Node, rtt time.Duration, payload []byte) {
+	d.nodePingDuration.WithLabelValues(peer.Name).Observe(rtt.Seconds())
+}
+
 // handleQueueDepth ensures that the queue doesn't grow unbounded by pruning
 // older messages at regular interval.
 func (d *delegate) handleQueueDepth() {