From 9e82caac45cd8eccd7b22c60c2cdbeec9aab3a2d Mon Sep 17 00:00:00 2001
From: reivilibre <oliverw@matrix.org>
Date: Tue, 6 Dec 2022 15:48:42 +0000
Subject: [PATCH] Faster remote room joins: unblock tasks waiting for full room
 state when the un-partial-stating of that room is received over the
 replication stream. [rei:frrj/streams/unpsr] (#14474)

---
 changelog.d/14474.misc                        |  1 +
 synapse/replication/tcp/client.py             | 11 ++++
 .../tcp/streams/test_partial_state.py         | 65 +++++++++++++++++++
 3 files changed, 77 insertions(+)
 create mode 100644 changelog.d/14474.misc
 create mode 100644 tests/replication/tcp/streams/test_partial_state.py

diff --git a/changelog.d/14474.misc b/changelog.d/14474.misc
new file mode 100644
index 000000000..deccd4e91
--- /dev/null
+++ b/changelog.d/14474.misc
@@ -0,0 +1 @@
+Faster remote room joins: stream the un-partial-stating of rooms over replication.
\ No newline at end of file
diff --git a/synapse/replication/tcp/client.py b/synapse/replication/tcp/client.py
index 18252a295..b4dad47b4 100644
--- a/synapse/replication/tcp/client.py
+++ b/synapse/replication/tcp/client.py
@@ -36,12 +36,14 @@ from synapse.replication.tcp.streams import (
     TagAccountDataStream,
     ToDeviceStream,
     TypingStream,
+    UnPartialStatedRoomStream,
 )
 from synapse.replication.tcp.streams.events import (
     EventsStream,
     EventsStreamEventRow,
     EventsStreamRow,
 )
+from synapse.replication.tcp.streams.partial_state import UnPartialStatedRoomStreamRow
 from synapse.types import PersistedEventPosition, ReadReceipt, StreamKeyType, UserID
 from synapse.util.async_helpers import Linearizer, timeout_deferred
 from synapse.util.metrics import Measure
@@ -117,6 +119,7 @@ class ReplicationDataHandler:
         self._streams = hs.get_replication_streams()
         self._instance_name = hs.get_instance_name()
         self._typing_handler = hs.get_typing_handler()
+        self._state_storage_controller = hs.get_storage_controllers().state
 
         self._notify_pushers = hs.config.worker.start_pushers
         self._pusher_pool = hs.get_pusherpool()
@@ -236,6 +239,14 @@ class ReplicationDataHandler:
                     self.notifier.notify_user_joined_room(
                         row.data.event_id, row.data.room_id
                     )
+        elif stream_name == UnPartialStatedRoomStream.NAME:
+            for row in rows:
+                assert isinstance(row, UnPartialStatedRoomStreamRow)
+
+                # Wake up any tasks waiting for the room to be un-partial-stated.
+                self._state_storage_controller.notify_room_un_partial_stated(
+                    row.room_id
+                )
 
         await self._presence_handler.process_replication_rows(
             stream_name, instance_name, token, rows
diff --git a/tests/replication/tcp/streams/test_partial_state.py b/tests/replication/tcp/streams/test_partial_state.py
new file mode 100644
index 000000000..2c10eab4d
--- /dev/null
+++ b/tests/replication/tcp/streams/test_partial_state.py
@@ -0,0 +1,65 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from twisted.internet.defer import ensureDeferred
+
+from synapse.rest.client import room
+
+from tests.replication._base import BaseMultiWorkerStreamTestCase
+
+
+class PartialStateStreamsTestCase(BaseMultiWorkerStreamTestCase):
+    servlets = [room.register_servlets]
+    hijack_auth = True
+    user_id = "@bob:test"
+
+    def setUp(self):
+        super().setUp()
+        self.store = self.hs.get_datastores().main
+
+    def test_un_partial_stated_room_unblocks_over_replication(self) -> None:
+        """
+        Tests that, when a room is un-partial-stated on another worker,
+        pending calls to `await_full_state` get unblocked.
+        """
+
+        # Make a room.
+        room_id = self.helper.create_room_as("@bob:test")
+        # Mark the room as partial-stated.
+        self.get_success(
+            self.store.store_partial_state_room(room_id, ["serv1", "serv2"], 0, "serv1")
+        )
+
+        worker = self.make_worker_hs("synapse.app.generic_worker")
+
+        # On the worker, attempt to get the current hosts in the room
+        d = ensureDeferred(
+            worker.get_storage_controllers().state.get_current_hosts_in_room(room_id)
+        )
+
+        self.reactor.advance(0.1)
+
+        # This should block
+        self.assertFalse(
+            d.called, "get_current_hosts_in_room/await_full_state did not block"
+        )
+
+        # On the master, clear the partial state flag.
+        self.get_success(self.store.clear_partial_state_room(room_id))
+
+        self.reactor.advance(0.1)
+
+        # The worker should have unblocked
+        self.assertTrue(
+            d.called, "get_current_hosts_in_room/await_full_state did not unblock"
+        )