From c1d7dbd4fc9865eb31931804b914e2d505dad56e Mon Sep 17 00:00:00 2001
From: David Zhao <dz@livekit.io>
Date: Mon, 19 Dec 2022 14:30:14 -0800
Subject: [PATCH] Tweaks to prometheus participant counter (#1240)

* Tweaks to prometheus participant counter

Ensure that we don't miss adding a count in migration scenarios

* avoid nil ICEConfig
---
 pkg/rtc/transportmanager.go |  1 +
 pkg/telemetry/events.go     | 12 +++++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/pkg/rtc/transportmanager.go b/pkg/rtc/transportmanager.go
index 1df76e823..131255046 100644
--- a/pkg/rtc/transportmanager.go
+++ b/pkg/rtc/transportmanager.go
@@ -83,6 +83,7 @@ func NewTransportManager(params TransportManagerParams) (*TransportManager, erro
 	t := &TransportManager{
 		params:         params,
 		mediaLossProxy: NewMediaLossProxy(MediaLossProxyParams{Logger: params.Logger}),
+		iceConfig:      &livekit.ICEConfig{},
 	}
 	t.mediaLossProxy.OnMediaLossUpdate(t.onMediaLossUpdate)
 
diff --git a/pkg/telemetry/events.go b/pkg/telemetry/events.go
index e68dfb3c1..bb39b372d 100644
--- a/pkg/telemetry/events.go
+++ b/pkg/telemetry/events.go
@@ -110,6 +110,8 @@ func (t *telemetryService) ParticipantActive(
 
 		worker, ok := t.getWorker(livekit.ParticipantID(participant.Sid))
 		if !ok {
+			// in case of session migration, we may not have seen a Join event take place.
+			// we'd need to create the worker here before being able to process events
 			worker = t.createWorker(
 				ctx,
 				livekit.RoomID(room.Sid),
@@ -117,6 +119,9 @@ func (t *telemetryService) ParticipantActive(
 				livekit.ParticipantID(participant.Sid),
 				livekit.ParticipantIdentity(participant.Identity),
 			)
+
+			// need to also account for participant count
+			prometheus.AddParticipant()
 		}
 		worker.SetConnected()
 
@@ -138,12 +143,17 @@ func (t *telemetryService) ParticipantLeft(ctx context.Context,
 ) {
 	t.enqueue(func() {
 		isConnected := false
+		hasWorker := false
 		if worker, ok := t.getWorker(livekit.ParticipantID(participant.Sid)); ok {
+			hasWorker = true
 			isConnected = worker.IsConnected()
 			worker.Close()
 		}
 
-		prometheus.SubParticipant()
+		if hasWorker {
+			// signifies we had incremented participant count
+			prometheus.SubParticipant()
+		}
 
 		if isConnected && shouldSendEvent {
 			t.NotifyEvent(ctx, &livekit.WebhookEvent{