Revert pruning of old devices (#15360)

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

This reverts commit f0d8f66eaaacfa75bed65bc5d0c602fbc5339c85.

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

This reverts commit 78cdb72cd6b0e007c314d9fed9f629dfc5b937a6.

9 files changed, 7 insertions, 187 deletions

diff --git a/changelog.d/15183.misc b/changelog.d/15183.misc
deleted file mode 100644
index f9bfc581ad..0000000000
--- a/changelog.d/15183.misc
+++ /dev/null
@@ -1 +0,0 @@
-Prune user's old devices on login if they have too many.
diff --git a/changelog.d/15348.misc b/changelog.d/15348.misc
deleted file mode 100644
index f9bfc581ad..0000000000
--- a/changelog.d/15348.misc
+++ /dev/null
@@ -1 +0,0 @@
-Prune user's old devices on login if they have too many.
diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py
index 0fc165a8d6..9ded6389ac 100644
--- a/synapse/handlers/device.py
+++ b/synapse/handlers/device.py
@@ -485,7 +485,7 @@ class DeviceHandler(DeviceWorkerHandler):
             device_ids = [d for d in device_ids if d != except_device_id]
         await self.delete_devices(user_id, device_ids)
 
-    async def delete_devices(self, user_id: str, device_ids: StrCollection) -> None:
+    async def delete_devices(self, user_id: str, device_ids: List[str]) -> None:
         """Delete several devices
 
         Args:
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index 7e9d065f50..c8bf2439af 100644
--- a/synapse/handlers/register.py
+++ b/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:
diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index f61b7bc96e..5503621ad6 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -1599,76 +1599,6 @@ class DeviceBackgroundUpdateStore(SQLBaseStore):
 
         return rows
 
-    async def check_too_many_devices_for_user(self, user_id: str) -> List[str]:
-        """Check if the user has a lot of devices, and if so return the set of
-        devices we can prune.
-
-        This does *not* return hidden devices or devices with E2E keys.
-        """
-
-        num_devices = await self.db_pool.simple_select_one_onecol(
-            table="devices",
-            keyvalues={"user_id": user_id, "hidden": False},
-            retcol="COALESCE(COUNT(*), 0)",
-            desc="count_devices",
-        )
-
-        # We let users have up to ten devices without pruning.
-        if num_devices <= 10:
-            return []
-
-        # We always prune devices not seen in the last 14 days...
-        max_last_seen = self._clock.time_msec() - 14 * 24 * 60 * 60 * 1000
-
-        # ... but we also cap the maximum number of devices the user can have to
-        # 50.
-        if num_devices > 50:
-            # Choose a last seen that ensures we keep at most 50 devices.
-            sql = """
-                SELECT last_seen FROM devices
-                LEFT JOIN e2e_device_keys_json USING (user_id, device_id)
-                WHERE
-                    user_id = ?
-                    AND NOT hidden
-                    AND last_seen IS NOT NULL
-                    AND key_json IS NULL
-                ORDER BY last_seen DESC
-                LIMIT 1
-                OFFSET 50
-            """
-
-            rows = await self.db_pool.execute(
-                "check_too_many_devices_for_user_last_seen",
-                None,
-                sql,
-                user_id,
-            )
-            if rows:
-                max_last_seen = max(rows[0][0], max_last_seen)
-
-        # Fetch the devices to delete.
-        sql = """
-            SELECT device_id FROM devices
-            LEFT JOIN e2e_device_keys_json USING (user_id, device_id)
-            WHERE
-                user_id = ?
-                AND NOT hidden
-                AND last_seen <= ?
-                AND key_json IS NULL
-            ORDER BY last_seen
-        """
-
-        def check_too_many_devices_for_user_txn(
-            txn: LoggingTransaction,
-        ) -> List[str]:
-            txn.execute(sql, (user_id, max_last_seen))
-            return [device_id for device_id, in txn]
-
-        return await self.db_pool.runInteraction(
-            "check_too_many_devices_for_user",
-            check_too_many_devices_for_user_txn,
-        )
-
 
 class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
     # Because we have write access, this will be a StreamIdGenerator
@@ -1727,7 +1657,6 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
                 values={},
                 insertion_values={
                     "display_name": initial_device_display_name,
-                    "last_seen": self._clock.time_msec(),
                     "hidden": False,
                 },
                 desc="store_device",
@@ -1773,15 +1702,7 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
             )
             raise StoreError(500, "Problem storing device.")
 
-    @cached(max_entries=0)
-    async def delete_device(self, user_id: str, device_id: str) -> None:
-        raise NotImplementedError()
-
-    # Note: sometimes deleting rows out of `device_inbox` can take a long time,
-    # so we use a cache so that we deduplicate in flight requests to delete
-    # devices.
-    @cachedList(cached_method_name="delete_device", list_name="device_ids")
-    async def delete_devices(self, user_id: str, device_ids: Collection[str]) -> dict:
+    async def delete_devices(self, user_id: str, device_ids: List[str]) -> None:
         """Deletes several devices.
 
         Args:
@@ -1818,8 +1739,6 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
         for device_id in device_ids:
             self.device_id_exists_cache.invalidate((user_id, device_id))
 
-        return {}
-
     async def update_device(
         self, user_id: str, device_id: str, new_display_name: Optional[str] = None
     ) -> None:
diff --git a/tests/handlers/test_admin.py b/tests/handlers/test_admin.py
index f0ba3775c8..5569ccef8a 100644
--- a/tests/handlers/test_admin.py
+++ b/tests/handlers/test_admin.py
@@ -272,7 +272,7 @@ class ExfiltrateData(unittest.HomeserverTestCase):
         self.assertIn("device_id", args[0][0])
         self.assertIsNone(args[0][0]["display_name"])
         self.assertIsNone(args[0][0]["last_seen_user_agent"])
-        self.assertEqual(args[0][0]["last_seen_ts"], 600)
+        self.assertIsNone(args[0][0]["last_seen_ts"])
         self.assertIsNone(args[0][0]["last_seen_ip"])
 
     def test_connections(self) -> None:
diff --git a/tests/handlers/test_device.py b/tests/handlers/test_device.py
index a456bffd63..ce7525e29c 100644
--- a/tests/handlers/test_device.py
+++ b/tests/handlers/test_device.py
@@ -115,7 +115,7 @@ class DeviceTestCase(unittest.HomeserverTestCase):
                 "device_id": "xyz",
                 "display_name": "display 0",
                 "last_seen_ip": None,
-                "last_seen_ts": 1000000,
+                "last_seen_ts": None,
             },
             device_map["xyz"],
         )
diff --git a/tests/rest/client/test_register.py b/tests/rest/client/test_register.py
index 7ae84e3139..b228dba861 100644
--- a/tests/rest/client/test_register.py
+++ b/tests/rest/client/test_register.py
@@ -794,53 +794,6 @@ class RegisterRestServletTestCase(unittest.HomeserverTestCase):
             ApprovalNoticeMedium.NONE, channel.json_body["approval_notice_medium"]
         )
 
-    def test_check_stale_devices_get_pruned(self) -> None:
-        """Check that if a user has some stale devices we log them out when they
-        log in a new device."""
-
-        # Register some devices, but not too many that we go over the threshold
-        # where we prune more aggressively.
-        user_id = self.register_user("user", "pass")
-        for _ in range(0, 50):
-            self.login(user_id, "pass")
-
-        store = self.hs.get_datastores().main
-
-        res = self.get_success(store.get_devices_by_user(user_id))
-        self.assertEqual(len(res), 50)
-
-        # Advance time so that the above devices are considered "old".
-        self.reactor.advance(30 * 24 * 60 * 60 * 1000)
-
-        self.login(user_id, "pass")
-
-        self.reactor.pump([60] * 10)  # Ensure background job runs
-
-        # We expect all old devices to have been logged out
-        res = self.get_success(store.get_devices_by_user(user_id))
-        self.assertEqual(len(res), 1)
-
-    def test_check_recent_devices_get_pruned(self) -> None:
-        """Check that if a user has many devices we log out the last oldest
-        ones.
-
-        Note: this is similar to above, except if we lots of devices we prune
-        devices even if they're not old.
-        """
-
-        # Register a lot of devices in a short amount of time
-        user_id = self.register_user("user", "pass")
-        for _ in range(0, 100):
-            self.login(user_id, "pass")
-            self.reactor.advance(100)
-
-        store = self.hs.get_datastores().main
-
-        # We keep up to 50 devices that have been used in the last week, plus
-        # the device that was last logged in.
-        res = self.get_success(store.get_devices_by_user(user_id))
-        self.assertEqual(len(res), 51)
-
 
 class AccountValidityTestCase(unittest.HomeserverTestCase):
     servlets = [
diff --git a/tests/storage/test_client_ips.py b/tests/storage/test_client_ips.py
index f989986538..cd0079871c 100644
--- a/tests/storage/test_client_ips.py
+++ b/tests/storage/test_client_ips.py
@@ -170,8 +170,6 @@ class ClientIpStoreTestCase(unittest.HomeserverTestCase):
             )
         )
 
-        last_seen = self.clock.time_msec()
-
         if after_persisting:
             # Trigger the storage loop
             self.reactor.advance(10)
@@ -192,7 +190,7 @@ class ClientIpStoreTestCase(unittest.HomeserverTestCase):
                         "device_id": device_id,
                         "ip": None,
                         "user_agent": None,
-                        "last_seen": last_seen,
+                        "last_seen": None,
                     },
                 ],
             )