From f253a361eac16060a74a2aa71a22afa98943d1c6 Mon Sep 17 00:00:00 2001
From: hechen-eng <he.chen@livekit.io>
Date: Mon, 9 Mar 2026 11:17:30 -0700
Subject: [PATCH] TEL-331: add start ringing metric

---
 pkg/sip/inbound.go   |  1 +
 pkg/stats/monitor.go | 14 ++++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/pkg/sip/inbound.go b/pkg/sip/inbound.go
index b4f53ed4..6eee60fd 100644
--- a/pkg/sip/inbound.go
+++ b/pkg/sip/inbound.go
@@ -679,6 +679,7 @@ func (c *inboundCall) handleInvite(ctx context.Context, tid traceid.ID, req *sip
 		c.call.SipCallId = h.Value()
 	}
 
+	c.mon.StartRingingDur().Observe(time.Since(c.callStart).Seconds())
 	c.cc.StartRinging()
 	// Send initial request. In the best case scenario, we will immediately get a room name to join.
 	// Otherwise, we could even learn that this number is not allowed and reject the call, or ask for pin if required.
diff --git a/pkg/stats/monitor.go b/pkg/stats/monitor.go
index 6c72c2b0..00d6dd76 100644
--- a/pkg/stats/monitor.go
+++ b/pkg/stats/monitor.go
@@ -72,6 +72,7 @@ type Monitor struct {
 	durCall                  *prometheus.HistogramVec
 	durJoin                  *prometheus.HistogramVec
 	durCheck                 *prometheus.HistogramVec
+	durStartRinging          *prometheus.HistogramVec
 	cpuLoad                  prometheus.Gauge
 	sdpSize                  *prometheus.HistogramVec
 	nodeAvailable            prometheus.GaugeFunc
@@ -214,6 +215,15 @@ func (m *Monitor) Start(conf *config.Config) error {
 		Buckets:     durBucketsOp,
 	}, []string{"dir"}))
 
+	m.durStartRinging = mustRegister(m, prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace:   "livekit",
+		Subsystem:   "sip",
+		Name:        "dur_start_ringing_sec",
+		Help:        "Duration from INVITE received to 180 Ringing sent",
+		ConstLabels: prometheus.Labels{"node_id": conf.NodeID},
+		Buckets:     durBucketsOp,
+	}, []string{"dir"}))
+
 	m.durJoin = mustRegister(m, prometheus.NewHistogramVec(prometheus.HistogramOpts{
 		Namespace:   "livekit",
 		Subsystem:   "sip",
@@ -428,6 +438,10 @@ func (c *CallMonitor) CheckDur() prometheus.Observer {
 	return c.m.durCheck.With(c.labelsShort(nil))
 }
 
+func (c *CallMonitor) StartRingingDur() prometheus.Observer {
+	return c.m.durStartRinging.With(c.labelsShort(nil))
+}
+
 func (c *CallMonitor) JoinDur() func() time.Duration {
 	return prometheus.NewTimer(c.m.durJoin.With(c.labelsShort(nil))).ObserveDuration
 }