2 files changed, 17 insertions, 5 deletions
diff --git a/changelog.d/14749.misc b/changelog.d/14749.misc
new file mode 100644
index 0000000000..ff81325225
--- /dev/null
+++ b/changelog.d/14749.misc
@@ -0,0 +1 @@
+Faster remote room joins (worker mode): do not populate external hosts-in-room cache when sending events as this requires blocking for full state.
\ No newline at end of file
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 88fc51a4c9..3278a695ed 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -1531,12 +1531,23 @@ class EventCreationHandler:
external federation senders don't have to recalculate it themselves.
"""
- for event, _ in events_and_context:
- if not self._external_cache.is_enabled():
- return
+ if not self._external_cache.is_enabled():
+ return
- # If external cache is enabled we should always have this.
- assert self._external_cache_joined_hosts_updates is not None
+ # If external cache is enabled we should always have this.
+ assert self._external_cache_joined_hosts_updates is not None
+
+ for event, event_context in events_and_context:
+ if event_context.partial_state:
+ # To populate the cache for a partial-state event, we either have to
+ # block until full state, which the code below does, or change the
+ # meaning of cache values to be the list of hosts to which we plan to
+ # send events and calculate that instead.
+ #
+ # The federation senders don't use the external cache when sending
+ # events in partial-state rooms anyway, so let's not bother populating
+ # the cache.
+ continue
# We actually store two mappings, event ID -> prev state group,
# state group -> joined hosts, which is much more space efficient
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