From 4ed9b5f90e0ecad588e00ebde48efa536ea9cfb3 Mon Sep 17 00:00:00 2001
From: Raja Subramanian <raja.gobi@tutanota.com>
Date: Tue, 31 May 2022 11:06:44 +0530
Subject: [PATCH] Revert "Using shadow pattern for stats workers (#742)" (#744)

This reverts commit 2b561d2bad3cb9087ef39bf37555f9a008751852.
---
 pkg/telemetry/telemetryserviceinternal.go     | 18 +++----
 .../telemetryserviceinternalevents.go         | 47 ++++++++++---------
 2 files changed, 35 insertions(+), 30 deletions(-)

diff --git a/pkg/telemetry/telemetryserviceinternal.go b/pkg/telemetry/telemetryserviceinternal.go
index beab7c302..68fca98e0 100644
--- a/pkg/telemetry/telemetryserviceinternal.go
+++ b/pkg/telemetry/telemetryserviceinternal.go
@@ -28,9 +28,9 @@ type telemetryServiceInternal struct {
 	webhookPool *workerpool.WorkerPool
 
 	// one worker per participant
-	workersMu     sync.RWMutex
-	workers       map[livekit.ParticipantID]*StatsWorker
-	workersShadow map[livekit.ParticipantID]*StatsWorker
+	workersMu  sync.RWMutex
+	workers    []*StatsWorker
+	workersIdx map[livekit.ParticipantID]int
 
 	analytics AnalyticsService
 }
@@ -39,7 +39,7 @@ func NewTelemetryServiceInternal(notifier webhook.Notifier, analytics AnalyticsS
 	return &telemetryServiceInternal{
 		notifier:    notifier,
 		webhookPool: workerpool.New(maxWebhookWorkers),
-		workers:     make(map[livekit.ParticipantID]*StatsWorker),
+		workersIdx:  make(map[livekit.ParticipantID]int),
 		analytics:   analytics,
 	}
 }
@@ -93,11 +93,13 @@ func (t *telemetryServiceInternal) Report(ctx context.Context, stats []*livekit.
 
 func (t *telemetryServiceInternal) SendAnalytics() {
 	t.workersMu.RLock()
-	workers := t.workersShadow
+	workers := t.workers
 	t.workersMu.RUnlock()
 
 	for _, worker := range workers {
-		worker.Update()
+		if worker != nil {
+			worker.Update()
+		}
 	}
 }
 
@@ -105,8 +107,8 @@ func (t *telemetryServiceInternal) getStatsWorker(participantID livekit.Particip
 	t.workersMu.RLock()
 	defer t.workersMu.RUnlock()
 
-	if worker, ok := t.workersShadow[participantID]; ok {
-		return worker
+	if idx, ok := t.workersIdx[participantID]; ok {
+		return t.workers[idx]
 	}
 
 	return nil
diff --git a/pkg/telemetry/telemetryserviceinternalevents.go b/pkg/telemetry/telemetryserviceinternalevents.go
index 8bb09ebd4..9f65b95ff 100644
--- a/pkg/telemetry/telemetryserviceinternalevents.go
+++ b/pkg/telemetry/telemetryserviceinternalevents.go
@@ -54,19 +54,30 @@ func (t *telemetryServiceInternal) ParticipantJoined(
 ) {
 	prometheus.IncrementParticipantJoin(1)
 
+	newWorker := newStatsWorker(
+		ctx,
+		t,
+		livekit.RoomID(room.Sid),
+		livekit.RoomName(room.Name),
+		livekit.ParticipantID(participant.Sid),
+		livekit.ParticipantIdentity(participant.Identity),
+	)
 	t.workersMu.Lock()
-	if _, ok := t.workers[livekit.ParticipantID(participant.Sid)]; !ok {
-		newWorker := newStatsWorker(
-			ctx,
-			t,
-			livekit.RoomID(room.Sid),
-			livekit.RoomName(room.Name),
-			livekit.ParticipantID(participant.Sid),
-			livekit.ParticipantIdentity(participant.Identity),
-		)
-		t.workers[livekit.ParticipantID(participant.Sid)] = newWorker
+	var free = false
+	for idx, worker := range t.workers {
+		if worker != nil {
+			continue
+		}
 
-		t.shadowWorkersLocked()
+		free = true
+		t.workersIdx[livekit.ParticipantID(participant.Sid)] = idx
+		t.workers[idx] = newWorker
+		break
+	}
+
+	if !free {
+		t.workersIdx[livekit.ParticipantID(participant.Sid)] = len(t.workers)
+		t.workers = append(t.workers, newWorker)
 	}
 	t.workersMu.Unlock()
 
@@ -109,10 +120,9 @@ func (t *telemetryServiceInternal) ParticipantLeft(ctx context.Context, room *li
 	}
 
 	t.workersMu.Lock()
-	if _, ok := t.workers[livekit.ParticipantID(participant.Sid)]; ok {
-		delete(t.workers, livekit.ParticipantID(participant.Sid))
-
-		t.shadowWorkersLocked()
+	if idx, ok := t.workersIdx[livekit.ParticipantID(participant.Sid)]; ok {
+		delete(t.workersIdx, livekit.ParticipantID(participant.Sid))
+		t.workers[idx] = nil
 	}
 	t.workersMu.Unlock()
 
@@ -330,10 +340,3 @@ func (t *telemetryServiceInternal) EgressEnded(ctx context.Context, info *liveki
 		RoomId:    info.RoomId,
 	})
 }
-
-func (t *telemetryServiceInternal) shadowWorkersLocked() {
-	t.workersShadow = make(map[livekit.ParticipantID]*StatsWorker, len(t.workers))
-	for pID, worker := range t.workers {
-		t.workersShadow[pID] = worker
-	}
-}