Enhances the autoupdate of projector by change-id

client/src/app/core/core-services/projector-data.service.ts

@@ -18,6 +18,21 @@ interface AllProjectorData {
     [id: number]: ProjectorData | { error: string };
 }
 
+/**
+ * Received data from server.
+ */
+interface ProjectorWebsocketMessage {
+    /**
+     * The `change_id` of the current update.
+     */
+    change_id: number;
+
+    /**
+     * The necessary new projector-data.
+     */
+    data: AllProjectorData;
+}
+
 /**
  * This service handles the websocket connection for the projector data.
  * Each projector instance registers itself by calling `getProjectorObservable`.
@@ -43,6 +58,11 @@ export class ProjectorDataService {
      */
     private readonly updateProjectorDataDebounceSubject = new Subject<void>();
 
+    /**
+     * Holds the current change id to check, if the update contains new content or a deprecated one.
+     */
+    private currentChangeId = 0;
+
     /**
      * Constructor.
      *
@@ -50,13 +70,17 @@ export class ProjectorDataService {
      */
     public constructor(private websocketService: WebsocketService) {
         // Dispatch projector data.
-        this.websocketService.getOberservable('projector').subscribe((update: AllProjectorData) => {
-            Object.keys(update).forEach(_id => {
+        this.websocketService.getOberservable('projector').subscribe((update: ProjectorWebsocketMessage) => {
+            if (this.currentChangeId > update.change_id) {
+                return;
+            }
+            Object.keys(update.data).forEach(_id => {
                 const id = parseInt(_id, 10);
                 if (this.currentProjectorData[id]) {
-                    this.currentProjectorData[id].next(update[id] as ProjectorData);
+                    this.currentProjectorData[id].next(update.data[id] as ProjectorData);
                 }
             });
+            this.currentChangeId = update.change_id;
         });
 
         // The service need to re-register, if the websocket connection was lost.

openslides/core/websocket.py

@@ -179,9 +179,7 @@ class ListenToProjectors(BaseWebsocketClientMessage):
             for projector_id, data in projector_data.items():
                 consumer.projector_hash[projector_id] = hash(str(data))
 
-            await consumer.send_json(
-                type="projector", content=projector_data, in_response=id
-            )
+            await consumer.send_projector_data(projector_data, in_response=id)
 
 
 class PingPong(BaseWebsocketClientMessage):

openslides/utils/autoupdate.py

@@ -217,7 +217,12 @@ def handle_changed_elements(elements: Iterable[Element]) -> None:
         # Send projector
         channel_layer = get_channel_layer()
         await channel_layer.group_send(
-            "projector", {"type": "projector_changed", "data": projector_data}
+            "projector",
+            {
+                "type": "projector_changed",
+                "data": projector_data,
+                "change_id": change_id,
+            },
         )
 
     if elements:

openslides/utils/consumers.py

@@ -190,6 +190,8 @@ class SiteConsumer(ProtocollAsyncJsonWebsocketConsumer):
         The projector has changed.
         """
         all_projector_data = event["data"]
+        change_id = event["change_id"]
+
         projector_data: Dict[int, Dict[str, Any]] = {}
         for projector_id in self.listen_projector_ids:
             data = all_projector_data.get(projector_id, [])
@@ -199,4 +201,19 @@ class SiteConsumer(ProtocollAsyncJsonWebsocketConsumer):
                 self.projector_hash[projector_id] = new_hash
 
         if projector_data:
-            await self.send_json(type="projector", content=projector_data)
+            await self.send_projector_data(projector_data, change_id=change_id)
+
+    async def send_projector_data(
+        self,
+        data: Dict[int, Dict[str, Any]],
+        change_id: Optional[int] = None,
+        in_response: Optional[str] = None,
+    ) -> None:
+        """
+        Sends projector data to the consumer.
+        """
+        if change_id is None:
+            change_id = await element_cache.get_current_change_id()
+
+        content = {"change_id": change_id, "data": data}
+        await self.send_json(type="projector", content=content, in_response=in_response)

tests/integration/utils/test_consumers.py

@@ -565,12 +565,15 @@ async def test_listen_to_projector(communicator, set_config):
     content = response.get("content")
     assert type == "projector"
     assert content == {
+        "change_id": 3,
+        "data": {
             "1": [
                 {
                     "data": {"name": "slide1", "event_name": "OpenSlides"},
                     "element": {"id": 1, "name": "test/slide1"},
                 }
             ]
+        },
     }
 
 
@@ -595,12 +598,15 @@ async def test_update_projector(communicator, set_config):
     content = response.get("content")
     assert type == "projector"
     assert content == {
+        "change_id": 4,
+        "data": {
             "1": [
                 {
                     "data": {"name": "slide1", "event_name": "Test Event"},
                     "element": {"id": 1, "name": "test/slide1"},
                 }
             ]
+        },
     }