Use past meetings to calc. estimated meeting size for LB

app/Models/Room.php

@@ -10,6 +10,7 @@
 use App\Observers\RoomObserver;
 use App\Settings\GeneralSettings;
 use App\Traits\AddsModelNameTrait;
+use HiFolks\Statistics\Stat;
 use Illuminate\Database\Eloquent\Attributes\ObservedBy;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
@@ -18,6 +19,7 @@
 use Illuminate\Database\Eloquent\Relations\HasMany;
 use Illuminate\Database\Eloquent\Relations\HasOne;
 use Illuminate\Support\Facades\Context;
+use Illuminate\Support\Facades\DB;
 use Illuminate\Validation\Rule;
 
 #[ObservedBy([RoomObserver::class])]
@@ -430,4 +432,54 @@ public function streaming(): HasOne
             ]
         )->chaperone('room');
     }
+
+    /**
+     * Get the estimated max participants of the room based on the last x meetings.
+     */
+    public function getEstimatedMaxParticipants(int $limit = 10): ?int
+    {
+        $meetings = $this->meetings()
+            ->whereNotNull('end')
+            ->whereNotNull('start')
+            ->limit($limit);
+
+        $db = DB::connection()->getConfig();
+
+        // Get only meetings that lasted at least 10 min.
+        switch ($db['driver']) {
+            case 'mariadb':
+            case 'mysql':
+                $meetings->whereRaw('end > start + INTERVAL 10 MINUTE');
+                break;
+            case 'pgsql':
+                $meetings->whereRaw("end - start > INTERVAL '10 minutes'");
+                break;
+            default:
+                throw new \Exception('Database driver not supported');
+        }
+
+        $meetings = $meetings->pluck('id');
+
+        if ($meetings->isEmpty()) {
+            return null;
+        }
+
+        $maxParticipants = MeetingStat::whereIn('meeting_id', $meetings)
+            ->groupBy('meeting_id')
+            ->selectRaw('max(participant_count) as max_participants')
+            ->orderBy('created_at')
+            ->pluck('max_participants');
+
+        if ($maxParticipants->isEmpty()) {
+            return null;
+        }
+
+        // Calculate weighted median
+        // Using median over average to compensate outliners
+        // Use a weighted median to give more weight to newer meetings, as they are more relevant for the future than older meetings
+        $weights = range(1, $maxParticipants->count());
+        $weightedMedian = Stat::weightedMedian($maxParticipants->toArray(), $weights);
+
+        return (int) ceil($weightedMedian);
+    }
 }

app/Plugins/Defaults/ServerLoadCalculationPlugin.php

@@ -5,10 +5,14 @@
 namespace App\Plugins\Defaults;
 
 use App\Plugins\Contracts\ServerLoadCalculationPluginContract;
+use BigBlueButton\Core\Meeting;
 use Carbon\Carbon;
 
 class ServerLoadCalculationPlugin implements ServerLoadCalculationPluginContract
 {
+    /**
+     * @param  Meeting[]  $meetings
+     */
     public function getLoad(array $meetings): int
     {
         $load = 0;
@@ -24,7 +28,12 @@ public function getLoad(array $meetings): int
 
                 // If meeting is in the starting phase, we use a higher number of users to calculate
                 // the load to compensate that the meeting will probably have more users in the future
-                $minUserCount = config('bigbluebutton.load_new_meeting_min_user_count');
+
+                // Use bbb-meeting-size-hint metadata if provided, fallback to fixed configurable value.
+                // (bbb-meeting-size-hint is set by PILOS based on previous meetings, other frontends e.g. an LMSs might set it to the class size, etc.)
+                $metadata = $meeting->getMetas();
+                $meetingSizeHint = isset($metadata['bbb-meeting-size-hint']) && is_numeric($metadata['bbb-meeting-size-hint']) ? (int) $metadata['bbb-meeting-size-hint'] : null;
+                $minUserCount = $meetingSizeHint ?? config('bigbluebutton.load_new_meeting_min_user_count');
 
                 // However if the meeting has a max user limit the meeting will never go over that limit,
                 // so we use the max user limit to calculate the load if it is lower than the min user count

app/Services/MeetingService.php

@@ -107,6 +107,11 @@ public function start(): ?CreateMeetingResponse
         $meetingParams->addMeta('bbb-origin', 'PILOS');
         $meetingParams->addMeta('pilos-sub-spool-dir', config('recording.spool-sub-directory'));
 
+        $estimatedMax = $this->meeting->room->getEstimatedMaxParticipants(config('bigbluebutton.meeting_size_hint_meetings_count'));
+        if ($estimatedMax !== null) {
+            $meetingParams->addMeta('bbb-meeting-size-hint', (string) $estimatedMax);
+        }
+
         // get files that should be used in this meeting and add links to the files
         $files = $this->meeting->room->files()->where('use_in_meeting', true)->orderBy('default', 'desc')->get();
         foreach ($files as $file) {

composer.json

@@ -17,6 +17,7 @@
     "ext-zip": "*",
     "directorytree/ldaprecord-laravel": "^4.0",
     "guzzlehttp/guzzle": "^7.0.1",
+    "hi-folks/statistics": "^1.5",
     "laravel/fortify": "^1.36",
     "laravel/framework": "^13.2",
     "laravel/horizon": "^5.21",

config/bigbluebutton.php

@@ -23,6 +23,7 @@
 
     'load_new_meeting_min_user_count' => (int) env('BBB_LOAD_MIN_USER_COUNT', 15),
     'load_new_meeting_min_user_interval' => (int) env('BBB_LOAD_MIN_USER_INTERVAL', 15),
+    'meeting_size_hint_meetings_count' => (int) env('BBB_MEETING_SIZE_HINT_MEETINGS_COUNT', 10),
 
     'allowed_name_characters' => env('BBB_ALLOWED_NAME_CHARACTERS', "\w ,.'\-+\/&()"),