neiam /apollos_crib

It's Apollo's Crib

Do not let an unresolvable anchor kill a Plani

b0906f0 · Gabriel Morell · 2026-09-05 20:37

6 files +27 -1

Message

{commit_body(@commit)}

modified apps/room_sanctum/lib/room_sanctum/workers/plani_worker.ex

+27 −1

@@ -123,7 +123,7 @@ defmodule RoomSanctum.Worker.Plani do

123	123	def handle_cast(:query, %{plani: nil} = state), do: {:noreply, state}
124	124
125	125	def handle_cast(:query, state) do
126		− {anchor, anchored_to, last_seen} = anchor(state.plani, state.last_seen)
	126	+ {anchor, anchored_to, last_seen} = resolve_anchor(state)
127	127
128	128	# Resolved on every tick rather than held: a source tinted since the last
129	129	# one should join without the Plani being edited, which is the whole point

@@ -192,6 +192,32 @@ defmodule RoomSanctum.Worker.Plani do

192	192
193	193	def handle_info(_msg, state), do: {:noreply, state}
194	194
	195	+ # The anchor, or the one it had.
	196	+ #
	197	+ # Resolving it reads the database -- which home foci this Plani has, and
	198	+ # where they are -- and a database that cannot answer took the worker down
	199	+ # on every tick, losing its state and its queries with it. That is a worse
	200	+ # outcome than a stale anchor: a Plani drawing from where it last knew is
	201	+ # wrong by however far the client has moved, while a Plani that keeps
	202	+ # restarting shows nothing at all and says only that it restarted.
	203	+ #
	204	+ # Loud, because the cause is nearly always a schema behind the code, and
	205	+ # that wants fixing rather than riding out.
	206	+ defp resolve_anchor(state) do
	207	+ anchor(state.plani, state.last_seen)
	208	+ rescue
	209	+ error ->
	210	+ Logger.warning(
	211	+ "plani#{state.id}: could not resolve an anchor, keeping the last one: " <>
	212	+ Exception.message(error)
	213	+ )
	214	+
	215	+ {state.anchor, state.anchored_to, state.last_seen}
	216	+ catch
	217	+ :exit, _reason ->
	218	+ {state.anchor, state.anchored_to, state.last_seen}
	219	+ end
	220	+
195	221	# Where to ask from: the client if it has said recently, a home foci if not.
196	222	#
197	223	# Takes and returns the last position this worker saw, because "which home"

Parents: bc42901