3 files changed, 62 insertions, 6 deletions
diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py
index 763f56dfc1..9e52af5f13 100644
--- a/synapse/handlers/device.py
+++ b/synapse/handlers/device.py
@@ -43,9 +43,12 @@ from synapse.metrics.background_process_metrics import (
 )
 from synapse.types import (
     JsonDict,
+    JsonMapping,
+    ScheduledTask,
     StrCollection,
     StreamKeyType,
     StreamToken,
+    TaskStatus,
     UserID,
     get_domain_from_id,
     get_verify_key_from_cross_signing_key,
@@ -62,6 +65,7 @@ if TYPE_CHECKING:
 
 logger = logging.getLogger(__name__)
 
+DELETE_DEVICE_MSGS_TASK_NAME = "delete_device_messages"
 MAX_DEVICE_DISPLAY_NAME_LEN = 100
 DELETE_STALE_DEVICES_INTERVAL_MS = 24 * 60 * 60 * 1000
 
@@ -78,6 +82,7 @@ class DeviceWorkerHandler:
         self._appservice_handler = hs.get_application_service_handler()
         self._state_storage = hs.get_storage_controllers().state
         self._auth_handler = hs.get_auth_handler()
+        self._event_sources = hs.get_event_sources()
         self.server_name = hs.hostname
         self._msc3852_enabled = hs.config.experimental.msc3852_enabled
         self._query_appservices_for_keys = (
@@ -386,6 +391,7 @@ class DeviceHandler(DeviceWorkerHandler):
         self._account_data_handler = hs.get_account_data_handler()
         self._storage_controllers = hs.get_storage_controllers()
         self.db_pool = hs.get_datastores().main.db_pool
+        self._task_scheduler = hs.get_task_scheduler()
 
         self.device_list_updater = DeviceListUpdater(hs, self)
 
@@ -419,6 +425,10 @@ class DeviceHandler(DeviceWorkerHandler):
                 self._delete_stale_devices,
             )
 
+        self._task_scheduler.register_action(
+            self._delete_device_messages, DELETE_DEVICE_MSGS_TASK_NAME
+        )
+
     def _check_device_name_length(self, name: Optional[str]) -> None:
         """
         Checks whether a device name is longer than the maximum allowed length.
@@ -530,6 +540,7 @@ class DeviceHandler(DeviceWorkerHandler):
             user_id: The user to delete devices from.
             device_ids: The list of device IDs to delete
         """
+        to_device_stream_id = self._event_sources.get_current_token().to_device_key
 
         try:
             await self.store.delete_devices(user_id, device_ids)
@@ -559,12 +570,49 @@ class DeviceHandler(DeviceWorkerHandler):
                     f"org.matrix.msc3890.local_notification_settings.{device_id}",
                 )
 
+            # Delete device messages asynchronously and in batches using the task scheduler
+            await self._task_scheduler.schedule_task(
+                DELETE_DEVICE_MSGS_TASK_NAME,
+                resource_id=device_id,
+                params={
+                    "user_id": user_id,
+                    "device_id": device_id,
+                    "up_to_stream_id": to_device_stream_id,
+                },
+            )
+
         # Pushers are deleted after `delete_access_tokens_for_user` is called so that
         # modules using `on_logged_out` hook can use them if needed.
         await self.hs.get_pusherpool().remove_pushers_by_devices(user_id, device_ids)
 
         await self.notify_device_update(user_id, device_ids)
 
+    DEVICE_MSGS_DELETE_BATCH_LIMIT = 100
+
+    async def _delete_device_messages(
+        self,
+        task: ScheduledTask,
+    ) -> Tuple[TaskStatus, Optional[JsonMapping], Optional[str]]:
+        """Scheduler task to delete device messages in batch of `DEVICE_MSGS_DELETE_BATCH_LIMIT`."""
+        assert task.params is not None
+        user_id = task.params["user_id"]
+        device_id = task.params["device_id"]
+        up_to_stream_id = task.params["up_to_stream_id"]
+
+        res = await self.store.delete_messages_for_device(
+            user_id=user_id,
+            device_id=device_id,
+            up_to_stream_id=up_to_stream_id,
+            limit=DeviceHandler.DEVICE_MSGS_DELETE_BATCH_LIMIT,
+        )
+
+        if res < DeviceHandler.DEVICE_MSGS_DELETE_BATCH_LIMIT:
+            return TaskStatus.COMPLETE, None, None
+        else:
+            # There is probably still device messages to be deleted, let's keep the task active and it will be run
+            # again in a subsequent scheduler loop run (probably the next one, if not too many tasks are running).
+            return TaskStatus.ACTIVE, None, None
+
     async def update_device(self, user_id: str, device_id: str, content: dict) -> None:
         """Update the given device
 
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index a4b05b72e7..375c7d0901 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -183,6 +183,7 @@ class BasePresenceHandler(abc.ABC):
     writer"""
 
     def __init__(self, hs: "HomeServer"):
+        self.hs = hs
         self.clock = hs.get_clock()
         self.store = hs.get_datastores().main
         self._storage_controllers = hs.get_storage_controllers()
@@ -473,8 +474,6 @@ class _NullContextManager(ContextManager[None]):
 class WorkerPresenceHandler(BasePresenceHandler):
     def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
-        self.hs = hs
-
         self._presence_writer_instance = hs.config.worker.writers.presence[0]
 
         # Route presence EDUs to the right worker
@@ -738,7 +737,6 @@ class WorkerPresenceHandler(BasePresenceHandler):
 class PresenceHandler(BasePresenceHandler):
     def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
-        self.hs = hs
         self.wheel_timer: WheelTimer[str] = WheelTimer()
         self.notifier = hs.get_notifier()
 
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 60a9f341b5..0ccd7d250c 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -40,6 +40,7 @@ from synapse.api.filtering import FilterCollection
 from synapse.api.presence import UserPresenceState
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS
 from synapse.events import EventBase
+from synapse.handlers.device import DELETE_DEVICE_MSGS_TASK_NAME
 from synapse.handlers.relations import BundledAggregations
 from synapse.logging import issue9533_logger
 from synapse.logging.context import current_context
@@ -268,6 +269,7 @@ class SyncHandler:
         self._storage_controllers = hs.get_storage_controllers()
         self._state_storage_controller = self._storage_controllers.state
         self._device_handler = hs.get_device_handler()
+        self._task_scheduler = hs.get_task_scheduler()
 
         self.should_calculate_push_rules = hs.config.push.enable_push
 
@@ -360,11 +362,19 @@ class SyncHandler:
         # (since we now know that the device has received them)
         if since_token is not None:
             since_stream_id = since_token.to_device_key
-            deleted = await self.store.delete_messages_for_device(
-                sync_config.user.to_string(), sync_config.device_id, since_stream_id
+            # Delete device messages asynchronously and in batches using the task scheduler
+            await self._task_scheduler.schedule_task(
+                DELETE_DEVICE_MSGS_TASK_NAME,
+                resource_id=sync_config.device_id,
+                params={
+                    "user_id": sync_config.user.to_string(),
+                    "device_id": sync_config.device_id,
+                    "up_to_stream_id": since_stream_id,
+                },
             )
             logger.debug(
-                "Deleted %d to-device messages up to %d", deleted, since_stream_id
+                "Deletion of to-device messages up to %d scheduled",
+                since_stream_id,
             )
 
         if timeout == 0 or since_token is None or full_state: