Start application service stream token tracking from 1 (#12193)

Co-authored-by: Erik Johnston <erik@matrix.org>

2 files changed, 3 insertions, 2 deletions

diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py

index 34d9411bbf..dace31d87e 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -1625,7 +1625,7 @@ class PresenceEventSource(EventSource[int, UserPresenceState]):
             # We'll actually pull the presence updates for these users at the end.
             interested_and_updated_users: Union[Set[str], FrozenSet[str]] = set()
 
-            if from_key:
+            if from_key is not None:
                 # First get all users that have had a presence update
                 updated_users = stream_change_cache.get_all_entities_changed(from_key)
 
diff --git a/synapse/storage/databases/main/appservice.py b/synapse/storage/databases/main/appservice.py

index 0694446558..abea4383c7 100644
--- a/synapse/storage/databases/main/appservice.py
+++ b/synapse/storage/databases/main/appservice.py
@@ -446,7 +446,8 @@ class ApplicationServiceTransactionWorkerStore(
             )
             last_stream_id = txn.fetchone()
             if last_stream_id is None or last_stream_id[0] is None:  # no row exists
-                return 0
+                # Stream tokens always start from 1, to avoid foot guns around `0` being falsey.
+                return 1
             else:
                 return int(last_stream_id[0])