Addresses performance issues for event dispatching: Copy the original event and delete the message data after a pre-defined timeout (Dash-Industry-Forum#4744)

Author: dsilhavy

index.d.ts

@@ -1656,7 +1656,7 @@ declare namespace dashjs {
             },
             events?: {
                 eventControllerRefreshDelay?: number,
-                deleteEventMessageDataAfterEventStarted?: boolean
+                deleteEventMessageDataTimeout?: number
             }
             timeShiftBuffer?: {
                 calcFromSegmentTimeline?: boolean

src/core/Settings.js

@@ -87,7 +87,7 @@ import Events from './events/Events.js';
  *            },
  *            events: {
  *              eventControllerRefreshDelay: 100,
- *              deleteEventMessageDataAfterEventStarted: true
+ *              deleteEventMessageDataTimeout: 10000
  *            }
  *            timeShiftBuffer: {
  *                calcFromSegmentTimeline: false,
@@ -352,10 +352,12 @@ import Events from './events/Events.js';
  * @typedef {Object} EventSettings
  * @property {number} [eventControllerRefreshDelay=100]
  * Interval timer used by the EventController to check if events need to be triggered or removed.
- * @property {boolean} [deleteEventMessageDataAfterEventStarted=true]
- * If this flag is enabled the EventController will delete the message data of events after they have been started. This is to save memory in case events have a long duration and need to be persisted in the EventController.
- * Note: Applications will receive a copy of the original event data when they subscribe to an event. This copy contains the original message data and is not affected by this setting.
- * Only if an event is dispatched for the second time (e.g. when the user seeks back) the message data will not be included in the dispatched event.
+ * @property {number} [deleteEventMessageDataTimeout=10000]
+ * If this value is larger than -1 the EventController will delete the message data attributes of events after they have been started and dispatched to the application.
+ * This is to save memory in case events have a long duration and need to be persisted in the EventController.
+ * This parameter defines the time in milliseconds between the start of an event and when the message data is deleted.
+ * If an event is dispatched for the second time (e.g. when the user seeks back) the message data will not be included in the dispatched event if it has been deleted already.
+ * Set this value to -1 to not delete any message data.
  */
 
 /**
@@ -1118,7 +1120,7 @@ function Settings() {
             },
             events: {
                 eventControllerRefreshDelay: 100,
-                deleteEventMessageDataAfterEventStarted: true
+                deleteEventMessageDataTimeout: 10000
             },
             timeShiftBuffer: {
                 calcFromSegmentTimeline: false,

src/streaming/controllers/EventController.js

@@ -477,7 +477,7 @@ function EventController() {
             if (mode === MediaPlayerEvents.EVENT_MODE_ON_RECEIVE && !event.triggeredReceivedEvent) {
                 logger.debug(`Received event ${eventId}`);
                 event.triggeredReceivedEvent = true;
-                eventBus.trigger(event.eventStream.schemeIdUri, { event: JSON.parse(JSON.stringify(event)) }, { mode });
+                eventBus.trigger(event.eventStream.schemeIdUri, { event }, { mode });
                 return;
             }
 
@@ -494,10 +494,12 @@ function EventController() {
                     _sendCallbackRequest(url);
                 } else {
                     logger.debug(`Starting event ${eventId} from period ${event.eventStream.period.id} at ${currentVideoTime}`);
-                    eventBus.trigger(event.eventStream.schemeIdUri, { event: JSON.parse(JSON.stringify(event)) }, { mode });
-                    if (settings.get().streaming.events.deleteEventMessageDataAfterEventStarted) {
-                        delete event.messageData;
-                        delete event.parsedMessageData;
+                    eventBus.trigger(event.eventStream.schemeIdUri, { event }, { mode });
+                    if (settings.get().streaming.events.deleteEventMessageDataTimeout > -1) {
+                        setTimeout(() => {
+                            delete event.messageData;
+                            delete event.parsedMessageData;
+                        }, settings.get().streaming.events.deleteEventMessageDataTimeout);
                     }
                 }
                 event.triggeredStartEvent = true;