From ee5947027014337784af29919ceed447a41efffc Mon Sep 17 00:00:00 2001
From: Alex Valiushko <alexvaliushko@tailscale.com>
Date: Fri, 19 Dec 2025 16:15:41 -0800
Subject: [PATCH] net/udprelay: remove tailscaled_peer_relay_endpoints_total
 (#18254)

This gauge will be reworked to include endpoint state in future.

Updates tailscale/corp#30820

Change-Id: I66f349d89422b46eec4ecbaf1a99ad656c7301f9

Signed-off-by: Alex Valiushko <alexvaliushko@tailscale.com>
---
 net/udprelay/metrics.go      | 25 -------------------------
 net/udprelay/metrics_test.go |  9 ---------
 net/udprelay/server.go       |  2 --
 3 files changed, 36 deletions(-)

diff --git a/net/udprelay/metrics.go b/net/udprelay/metrics.go
index 45d3c9f34..b7c0710c2 100644
--- a/net/udprelay/metrics.go
+++ b/net/udprelay/metrics.go
@@ -22,10 +22,6 @@ var (
 	cMetricForwarded46Bytes = clientmetric.NewAggregateCounter("udprelay_forwarded_bytes_udp4_udp6")
 	cMetricForwarded64Bytes = clientmetric.NewAggregateCounter("udprelay_forwarded_bytes_udp6_udp4")
 	cMetricForwarded66Bytes = clientmetric.NewAggregateCounter("udprelay_forwarded_bytes_udp6_udp6")
-
-	// [clientmetric.Gauge] does not let us embed existing counters,
-	// [metrics.addEndpoints] records data into client and user gauges independently.
-	cMetricEndpoints = clientmetric.NewGauge("udprelay_endpoints")
 )
 
 type transport string
@@ -40,9 +36,6 @@ type forwardedLabel struct {
 	transportOut transport `prom:"transport_out"`
 }
 
-type endpointLabel struct {
-}
-
 type metrics struct {
 	forwarded44Packets expvar.Int
 	forwarded46Packets expvar.Int
@@ -53,8 +46,6 @@ type metrics struct {
 	forwarded46Bytes expvar.Int
 	forwarded64Bytes expvar.Int
 	forwarded66Bytes expvar.Int
-
-	endpoints expvar.Int
 }
 
 // registerMetrics publishes user and client metric counters for peer relay server.
@@ -74,12 +65,6 @@ func registerMetrics(reg *usermetric.Registry) *metrics {
 			"counter",
 			"Number of bytes forwarded via Peer Relay",
 		)
-		uMetricEndpoints = usermetric.NewMultiLabelMapWithRegistry[endpointLabel](
-			reg,
-			"tailscaled_peer_relay_endpoints_total",
-			"gauge",
-			"Number of allocated Peer Relay endpoints",
-		)
 		forwarded44 = forwardedLabel{transportIn: transportUDP4, transportOut: transportUDP4}
 		forwarded46 = forwardedLabel{transportIn: transportUDP4, transportOut: transportUDP6}
 		forwarded64 = forwardedLabel{transportIn: transportUDP6, transportOut: transportUDP4}
@@ -98,8 +83,6 @@ func registerMetrics(reg *usermetric.Registry) *metrics {
 	uMetricForwardedBytes.Set(forwarded64, &m.forwarded64Bytes)
 	uMetricForwardedBytes.Set(forwarded66, &m.forwarded66Bytes)
 
-	uMetricEndpoints.Set(endpointLabel{}, &m.endpoints)
-
 	// Publish client metrics.
 	cMetricForwarded44Packets.Register(&m.forwarded44Packets)
 	cMetricForwarded46Packets.Register(&m.forwarded46Packets)
@@ -113,13 +96,6 @@ func registerMetrics(reg *usermetric.Registry) *metrics {
 	return m
 }
 
-// addEndpoints updates the total endpoints gauge. Value can be negative.
-// It records two gauges independently, see [cMetricEndpoints] doc.
-func (m *metrics) addEndpoints(value int64) {
-	m.endpoints.Add(value)
-	cMetricEndpoints.Add(value)
-}
-
 // countForwarded records user and client metrics according to the
 // inbound and outbound address families.
 func (m *metrics) countForwarded(in4, out4 bool, bytes, packets int64) {
@@ -149,5 +125,4 @@ func deregisterMetrics() {
 	cMetricForwarded46Bytes.UnregisterAll()
 	cMetricForwarded64Bytes.UnregisterAll()
 	cMetricForwarded66Bytes.UnregisterAll()
-	cMetricEndpoints.Set(0)
 }
diff --git a/net/udprelay/metrics_test.go b/net/udprelay/metrics_test.go
index 25345dc6b..5c6a75113 100644
--- a/net/udprelay/metrics_test.go
+++ b/net/udprelay/metrics_test.go
@@ -22,20 +22,11 @@ func TestMetrics(t *testing.T) {
 	want := []string{
 		"tailscaled_peer_relay_forwarded_packets_total",
 		"tailscaled_peer_relay_forwarded_bytes_total",
-		"tailscaled_peer_relay_endpoints_total",
 	}
 	slices.Sort(have)
 	slices.Sort(want)
 	c.Assert(have, qt.CmpEquals(), want)
 
-	// Validate addEndpoints.
-	m.addEndpoints(1)
-	c.Assert(m.endpoints.Value(), qt.Equals, int64(1))
-	c.Assert(cMetricEndpoints.Value(), qt.Equals, int64(1))
-	m.addEndpoints(-1)
-	c.Assert(m.endpoints.Value(), qt.Equals, int64(0))
-	c.Assert(cMetricEndpoints.Value(), qt.Equals, int64(0))
-
 	// Validate countForwarded.
 	m.countForwarded(true, true, 1, 1)
 	c.Assert(m.forwarded44Bytes.Value(), qt.Equals, int64(1))
diff --git a/net/udprelay/server.go b/net/udprelay/server.go
index e98fdf7bb..acdbf5ad6 100644
--- a/net/udprelay/server.go
+++ b/net/udprelay/server.go
@@ -673,7 +673,6 @@ func (s *Server) endpointGCLoop() {
 		defer s.mu.Unlock()
 		for k, v := range s.serverEndpointByDisco {
 			if v.isExpired(now, s.bindLifetime, s.steadyStateLifetime) {
-				s.metrics.addEndpoints(-1)
 				delete(s.serverEndpointByDisco, k)
 				s.serverEndpointByVNI.Delete(v.vni)
 			}
@@ -969,7 +968,6 @@ func (s *Server) AllocateEndpoint(discoA, discoB key.DiscoPublic) (endpoint.Serv
 	s.serverEndpointByVNI.Store(e.vni, e)
 
 	s.logf("allocated endpoint vni=%d lamportID=%d disco[0]=%v disco[1]=%v", e.vni, e.lamportID, pair.Get()[0].ShortString(), pair.Get()[1].ShortString())
-	s.metrics.addEndpoints(1)
 	return endpoint.ServerEndpoint{
 		ServerDisco:         s.discoPublic,
 		ClientDisco:         pair.Get(),