Avoid sharing room hierarchy responses between users

changelog.d/11355.bugfix

@@ -0,0 +1 @@
+Fix a bug introduced in 1.41.0 where space hierarchy responses would be incorrectly reused if multiple users were to make the same request at the same time.

synapse/handlers/room_summary.py

@@ -97,7 +97,7 @@ def __init__(self, hs: "HomeServer"):
  # If a user tries to fetch the same page multiple times in quick succession,
  # only process the first attempt and return its result to subsequent requests.
  self._pagination_response_cache: ResponseCache[
- Tuple[str, bool, Optional[int], Optional[int], Optional[str]]
+ Tuple[str, str, bool, Optional[int], Optional[int], Optional[str]]
  ] = ResponseCache(
  hs.get_clock(),
  "get_room_hierarchy",
@@ -282,7 +282,14 @@ async def get_room_hierarchy(
  # This is due to the pagination process mutating internal state, attempting
  # to process multiple requests for the same page will result in errors.
  return await self._pagination_response_cache.wrap(
- (requested_room_id, suggested_only, max_depth, limit, from_token),
+ (
+ requester,
+ requested_room_id,
+ suggested_only,
+ max_depth,
+ limit,
+ from_token,
+ ),
  self._get_room_hierarchy,
  requester,
  requested_room_id,

tests/handlers/test_room_summary.py

@@ -14,6 +14,8 @@
 from typing import Any, Iterable, List, Optional, Tuple
 from unittest import mock
 
+from twisted.internet.defer import ensureDeferred
+
 from synapse.api.constants import (
  EventContentFields,
  EventTypes,
@@ -316,6 +318,59 @@ def test_visibility(self):
  AuthError,
  )
 
+ def test_room_hierarchy_cache(self) -> None:
+ """In-flight room hierarchy requests are deduplicated."""
+ # Run two `get_room_hierarchy` calls up until they block.
+ deferred1 = ensureDeferred(
+ self.handler.get_room_hierarchy(self.user, self.space)
+ )
+ deferred2 = ensureDeferred(
+ self.handler.get_room_hierarchy(self.user, self.space)
+ )
+
+ # Complete the two calls.
+ result1 = self.get_success(deferred1)
+ result2 = self.get_success(deferred2)
+
+ # Both `get_room_hierarchy` calls should return the same result.
+ expected = [(self.space, [self.room]), (self.room, ())]
+ self._assert_hierarchy(result1, expected)
+ self._assert_hierarchy(result2, expected)
+ self.assertIs(result1, result2)
+
+ # A subsequent `get_room_hierarchy` call should not reuse the result.
+ result3 = self.get_success(
+ self.handler.get_room_hierarchy(self.user, self.space)
+ )
+ self._assert_hierarchy(result3, expected)
+ self.assertIsNot(result1, result3)
+
+ def test_room_hierarchy_cache_sharing(self) -> None:
+ """Room hierarchy responses for different users are not shared."""
+ user2 = self.register_user("user2", "pass")
+
+ # Make the room within the space invite-only.
+ self.helper.send_state(
+ self.room,
+ event_type=EventTypes.JoinRules,
+ body={"join_rule": JoinRules.INVITE},
+ tok=self.token,
+ )
+
+ # Run two `get_room_hierarchy` calls for different users up until they block.
+ deferred1 = ensureDeferred(
+ self.handler.get_room_hierarchy(self.user, self.space)
+ )
+ deferred2 = ensureDeferred(self.handler.get_room_hierarchy(user2, self.space))
+
+ # Complete the two calls.
+ result1 = self.get_success(deferred1)
+ result2 = self.get_success(deferred2)
+
+ # The `get_room_hierarchy` calls should return different results.
+ self._assert_hierarchy(result1, [(self.space, [self.room]), (self.room, ())])
+ self._assert_hierarchy(result2, [(self.space, [self.room])])
+
  def _create_room_with_join_rule(
  self, join_rule: str, room_version: Optional[str] = None, **extra_content
  ) -> str: