Faster joins: send heroes to handle nameless rooms

[richvdh]

No description provided.

[richvdh]

we will need to pass through heroes, to ensure that rooms without their own name get a useful title ("Bob and 4 others", etc)

[DMRobertson]

Is this something we can make progress on today? Does the initial set of state events sent from the resident server include the heroes' membership events?

Edit: or is the point that we need to calculate those membership events and include them in the partial join response?

[richvdh]

yes, the latter: we need to extend the response from /send_join to include heroes.

[DMRobertson]

synapse/synapse/federation/federation_server.py

Lines 1495 to 1528 in 70b3396

	def _get_event_ids_for_partial_state_join(
	join_event: EventBase,
	prev_state_ids: StateMap[str],
	) -> Collection[str]:
	"""Calculate state to be retuned in a partial_state send_join
	Args:
	join_event: the join event being send_joined
	prev_state_ids: the event ids of the state before the join
	Returns:
	the event ids to be returned
	"""
	# return all non-member events
	state_event_ids = {
	event_id
	for (event_type, state_key), event_id in prev_state_ids.items()
	if event_type != EventTypes.Member
	}
	# we also need the current state of the current user (it's going to
	# be an auth event for the new join, so we may as well return it)
	current_membership_event_id = prev_state_ids.get(
	(EventTypes.Member, join_event.state_key)
	)
	if current_membership_event_id is not None:
	state_event_ids.add(current_membership_event_id)
	# TODO: return a few more members:
	# - those with invites
	# - those that are kicked? / banned
	return state_event_ids

seems like it's a good place to start.