Refuse to start when `faster_joins` is enabled on a worker deployment (#13531)

Synapse does not currently support faster room joins on deployments with
workers.

Signed-off-by: Sean Quah <seanq@matrix.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/synapse/app/generic_worker.py b/synapse/app/generic_worker.py

index 42d1f6d219..30e21d9707 100644
--- a/synapse/app/generic_worker.py
+++ b/synapse/app/generic_worker.py
@@ -441,6 +441,13 @@ def start(config_options: List[str]) -> None:
         "synapse.app.user_dir",
     )
 
+    if config.experimental.faster_joins_enabled:
+        raise ConfigError(
+            "You have enabled the experimental `faster_joins` config option, but it is "
+            "not compatible with worker deployments yet. Please disable `faster_joins` "
+            "or run Synapse as a single process deployment instead."
+        )
+
     synapse.events.USE_FROZEN_DICTS = config.server.use_frozen_dicts
     synapse.util.caches.TRACK_MEMORY_USAGE = config.caches.track_memory_usage