Revert pruning of old devices (#15360)

* Revert "Fix registering a device on an account with lots of devices (#15348)"

This reverts commit f0d8f66eaa.

* Revert "Delete stale non-e2e devices for users, take 3 (#15183)"

This reverts commit 78cdb72cd6.

synapse/handlers/register.py

@@ -16,7 +16,7 @@
 """Contains functions for registering clients."""
 
 import logging
-from typing import TYPE_CHECKING, Iterable, List, Optional, Set, Tuple
+from typing import TYPE_CHECKING, Iterable, List, Optional, Tuple
 
 from prometheus_client import Counter
 from typing_extensions import TypedDict
@@ -40,7 +40,6 @@ from synapse.appservice import ApplicationService
 from synapse.config.server import is_threepid_reserved
 from synapse.handlers.device import DeviceHandler
 from synapse.http.servlet import assert_params_in_dict
-from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.replication.http.login import RegisterDeviceReplicationServlet
 from synapse.replication.http.register import (
     ReplicationPostRegisterActionsServlet,
@@ -49,7 +48,6 @@ from synapse.replication.http.register import (
 from synapse.spam_checker_api import RegistrationBehaviour
 from synapse.types import RoomAlias, UserID, create_requester
 from synapse.types.state import StateFilter
-from synapse.util.iterutils import batch_iter
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
@@ -112,10 +110,6 @@ class RegistrationHandler:
         self._server_notices_mxid = hs.config.servernotices.server_notices_mxid
         self._server_name = hs.hostname
 
-        # The set of users that we're currently pruning devices for. Ensures
-        # that we don't have two such jobs for the same user running at once.
-        self._currently_pruning_devices_for_users: Set[str] = set()
-
         self.spam_checker = hs.get_spam_checker()
 
         if hs.config.worker.worker_app:
@@ -127,10 +121,7 @@ class RegistrationHandler:
                 ReplicationPostRegisterActionsServlet.make_client(hs)
             )
         else:
-            device_handler = hs.get_device_handler()
-            assert isinstance(device_handler, DeviceHandler)
-            self.device_handler = device_handler
-
+            self.device_handler = hs.get_device_handler()
             self._register_device_client = self.register_device_inner
             self.pusher_pool = hs.get_pusherpool()
 
@@ -860,9 +851,6 @@ class RegistrationHandler:
         # This can only run on the main process.
         assert isinstance(self.device_handler, DeviceHandler)
 
-        # Prune the user's device list if they already have a lot of devices.
-        await self._maybe_prune_too_many_devices(user_id)
-
         registered_device_id = await self.device_handler.check_device_registered(
             user_id,
             device_id,
@@ -931,42 +919,6 @@ class RegistrationHandler:
             "refresh_token": refresh_token,
         }
 
-    async def _maybe_prune_too_many_devices(self, user_id: str) -> None:
-        """Delete any excess old devices this user may have."""
-
-        if user_id in self._currently_pruning_devices_for_users:
-            return
-
-        # We also cap the number of users whose devices we prune at the same
-        # time, to avoid performance problems.
-        if len(self._currently_pruning_devices_for_users) > 5:
-            return
-
-        device_ids = await self.store.check_too_many_devices_for_user(user_id)
-        if not device_ids:
-            return
-
-        logger.info("Pruning %d stale devices for %s", len(device_ids), user_id)
-
-        # Now spawn a background loop that deletes said devices.
-        async def _prune_too_many_devices_loop() -> None:
-            if user_id in self._currently_pruning_devices_for_users:
-                return
-
-            self._currently_pruning_devices_for_users.add(user_id)
-
-            try:
-                for batch in batch_iter(device_ids, 10):
-                    await self.device_handler.delete_devices(user_id, batch)
-
-                    await self.clock.sleep(60)
-            finally:
-                self._currently_pruning_devices_for_users.discard(user_id)
-
-        run_as_background_process(
-            "_prune_too_many_devices_loop", _prune_too_many_devices_loop
-        )
-
     async def post_registration_actions(
         self, user_id: str, auth_result: dict, access_token: Optional[str]
     ) -> None: