Fix device list update to not constantly resync

1 files changed, 115 insertions, 46 deletions

diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py
index ca7137f315..23dab53df1 100644
--- a/synapse/handlers/device.py
+++ b/synapse/handlers/device.py
@@ -34,10 +34,11 @@ class DeviceHandler(BaseHandler):
         self.state = hs.get_state_handler()
         self.federation_sender = hs.get_federation_sender()
         self.federation = hs.get_replication_layer()
-        self._remote_edue_linearizer = Linearizer(name="remote_device_list")
+
+        self._edu_updater = DeviceListEduUpdater(hs, self)
 
         self.federation.register_edu_handler(
-            "m.device_list_update", self._incoming_device_list_update,
+            "m.device_list_update", self._edu_updater.incoming_device_list_update,
         )
         self.federation.register_query_handler(
             "user_devices", self.on_federation_query_user_devices,
@@ -299,13 +300,63 @@ class DeviceHandler(BaseHandler):
         # and those that actually still share a room with the user
         defer.returnValue(users_who_share_room & possibly_changed)
 
-    @measure_func("_incoming_device_list_update")
     @defer.inlineCallbacks
-    def _incoming_device_list_update(self, origin, edu_content):
-        user_id = edu_content["user_id"]
-        device_id = edu_content["device_id"]
-        stream_id = edu_content["stream_id"]
-        prev_ids = edu_content.get("prev_id", [])
+    def on_federation_query_user_devices(self, user_id):
+        stream_id, devices = yield self.store.get_devices_with_keys_by_user(user_id)
+        defer.returnValue({
+            "user_id": user_id,
+            "stream_id": stream_id,
+            "devices": devices,
+        })
+
+    @defer.inlineCallbacks
+    def user_left_room(self, user, room_id):
+        user_id = user.to_string()
+        rooms = yield self.store.get_rooms_for_user(user_id)
+        if not rooms:
+            # We no longer share rooms with this user, so we'll no longer
+            # receive device updates. Mark this in DB.
+            yield self.store.mark_remote_user_device_list_as_unsubscribed(user_id)
+
+
+def _update_device_from_client_ips(device, client_ips):
+    ip = client_ips.get((device["user_id"], device["device_id"]), {})
+    device.update({
+        "last_seen_ts": ip.get("last_seen"),
+        "last_seen_ip": ip.get("ip"),
+    })
+
+
+class DeviceListEduUpdater(object):
+    "Handles incoming device list updates from federation and updates the DB"
+
+    def __init__(self, hs, device_handler):
+        self.store = hs.get_datastore()
+        self.federation = hs.get_replication_layer()
+        self.clock = hs.get_clock()
+        self.device_handler = device_handler
+
+        self._remote_edue_linearizer = Linearizer(name="remote_device_list")
+
+        # user_id -> list of updates waiting to be handled.
+        self._pending_updates = {}
+
+        # Recently seen stream ids. We don't bother keeping these in the DB,
+        # but they're useful to have them about to reduce the number of spurious
+        # resyncs.
+        self._seen_updates = {}
+
+    @defer.inlineCallbacks
+    def incoming_device_list_update(self, origin, edu_content):
+        """Called on incoming device list update from federation. Responsible
+        for parsing the EDU and adding to pending updates list.
+        """
+
+        user_id = edu_content.pop("user_id")
+        device_id = edu_content.pop("device_id")
+        stream_id = str(edu_content.pop("stream_id"))  # They may come as ints
+        prev_ids = edu_content.pop("prev_id", [])
+        prev_ids = [str(p) for p in prev_ids]   # They may come as ints
 
         if get_domain_from_id(user_id) != origin:
             # TODO: Raise?
@@ -318,20 +369,28 @@ class DeviceHandler(BaseHandler):
             # probably won't get any further updates.
             return
 
+        self._pending_updates.setdefault(user_id, []).append(
+            (device_id, stream_id, prev_ids, edu_content)
+        )
+
+        yield self._handle_device_updates(user_id)
+
+    @measure_func("_incoming_device_list_update")
+    @defer.inlineCallbacks
+    def _handle_device_updates(self, user_id):
+        "Actually handle pending updates."
+
         with (yield self._remote_edue_linearizer.queue(user_id)):
-            # If the prev id matches whats in our cache table, then we don't need
-            # to resync the users device list, otherwise we do.
-            resync = True
-            if len(prev_ids) == 1:
-                extremity = yield self.store.get_device_list_last_stream_id_for_remote(
-                    user_id
-                )
-                logger.info("Extrem: %r, prev_ids: %r", extremity, prev_ids)
-                if str(extremity) == str(prev_ids[0]):
-                    resync = False
+            pending_updates = self._pending_updates.pop(user_id, [])
+            if not pending_updates:
+                # This can happen since we batch updates
+                return
+
+            resync = yield self._need_to_do_resync(user_id, pending_updates)
 
             if resync:
                 # Fetch all devices for the user.
+                origin = get_domain_from_id(user_id)
                 result = yield self.federation.query_user_devices(origin, user_id)
                 stream_id = result["stream_id"]
                 devices = result["devices"]
@@ -339,40 +398,50 @@ class DeviceHandler(BaseHandler):
                     user_id, devices, stream_id,
                 )
                 device_ids = [device["device_id"] for device in devices]
-                yield self.notify_device_update(user_id, device_ids)
+                yield self.device_handler.notify_device_update(user_id, device_ids)
             else:
                 # Simply update the single device, since we know that is the only
                 # change (becuase of the single prev_id matching the current cache)
-                content = dict(edu_content)
-                for key in ("user_id", "device_id", "stream_id", "prev_ids"):
-                    content.pop(key, None)
-                yield self.store.update_remote_device_list_cache_entry(
-                    user_id, device_id, content, stream_id,
+                for device_id, stream_id, prev_ids, content in pending_updates:
+                    yield self.store.update_remote_device_list_cache_entry(
+                        user_id, device_id, content, stream_id,
+                    )
+
+                yield self.device_handler.notify_device_update(
+                    user_id, [device_id for device_id, _, _, _ in pending_updates]
                 )
-                yield self.notify_device_update(user_id, [device_id])
 
-    @defer.inlineCallbacks
-    def on_federation_query_user_devices(self, user_id):
-        stream_id, devices = yield self.store.get_devices_with_keys_by_user(user_id)
-        defer.returnValue({
-            "user_id": user_id,
-            "stream_id": stream_id,
-            "devices": devices,
-        })
+            self._seen_updates.setdefault(user_id, set()).update(
+                [stream_id for _, stream_id, _, _ in pending_updates]
+            )
 
     @defer.inlineCallbacks
-    def user_left_room(self, user, room_id):
-        user_id = user.to_string()
-        rooms = yield self.store.get_rooms_for_user(user_id)
-        if not rooms:
-            # We no longer share rooms with this user, so we'll no longer
-            # receive device updates. Mark this in DB.
-            yield self.store.mark_remote_user_device_list_as_unsubscribed(user_id)
+    def _need_to_do_resync(self, user_id, updates):
+        """Given a list of updates for a user figure out if we need to do a full
+        resync, or whether we have enough data that we can just apply the delta.
+        """
+        seen_updates = self._seen_updates.get(user_id, set())
 
+        extremity = yield self.store.get_device_list_last_stream_id_for_remote(
+            user_id
+        )
 
-def _update_device_from_client_ips(device, client_ips):
-    ip = client_ips.get((device["user_id"], device["device_id"]), {})
-    device.update({
-        "last_seen_ts": ip.get("last_seen"),
-        "last_seen_ip": ip.get("ip"),
-    })
+        stream_id_in_updates = set()  # stream_ids in updates list
+        for _, stream_id, prev_ids, _ in updates:
+            if not prev_ids:
+                # We always do a resync if there are no previous IDs
+                defer.returnValue(True)
+
+            for prev_id in prev_ids:
+                if prev_id == extremity:
+                    continue
+                elif prev_id in seen_updates:
+                    continue
+                elif prev_id in stream_id_in_updates:
+                    continue
+                else:
+                    defer.returnValue(True)
+
+            stream_id_in_updates.add(stream_id)
+
+        defer.returnValue(False)