Remove the incoming_connection_timestamp metric (#965)

* Remove the incoming_connection_timestamp metric

metrics/metrics.go

@@ -200,14 +200,6 @@ var (
 		Help: "1 for drand nodes, not emitted for relays",
 	})
 
-	// IncomingConnectionTimestamp (Group) timestamp when each incoming connection was established
-	// We cannot track the actual connection state as with outgoing connections, since grpc-go
-	// doesn't allow for adding a listener for state tracking.
-	IncomingConnectionTimestamp = prometheus.NewGaugeVec(prometheus.GaugeOpts{
-		Name: "incoming_connection_timestamp",
-		Help: "timestamp when an incoming connection was established",
-	}, []string{"remote_host"})
-
 	// OutgoingConnectionState (Group) tracks the state of an outgoing connection, according to
 	// https://github.com/grpc/grpc-go/blob/master/connectivity/connectivity.go#L51
 	// Due to the fact that grpc-go doesn't support adding a listener for state tracking, this is
@@ -249,7 +241,6 @@ func bindMetrics() error {
 		drandBuildTime,
 		dkgStateChangeTimestamp,
 		reshareStateChangeTimestamp,
-		IncomingConnectionTimestamp,
 		OutgoingConnectionState,
 	}
 	for _, c := range group {

net/listener.go

@@ -55,7 +55,7 @@ func NewGRPCListenerForPrivate(
 	opts = append(opts,
 		grpc.StreamInterceptor(grpc_middleware.ChainStreamServer(grpc_prometheus.StreamServerInterceptor, s.NodeVersionStreamValidator)),
 		grpc.UnaryInterceptor(grpc_middleware.ChainUnaryServer(grpc_prometheus.UnaryServerInterceptor, s.NodeVersionValidator)),
-		grpc.StatsHandler(IncomingConnectionsStatsHandler))
+	)
 
 	grpcServer := grpc.NewServer(opts...)