Add ability to wait for locks and add locks to purge history / room deletion (#15791)

c.f. #13476

1 files changed, 16 insertions, 0 deletions

diff --git a/synapse/notifier.py b/synapse/notifier.py
index 897272ad5b..68115bca70 100644
--- a/synapse/notifier.py
+++ b/synapse/notifier.py
@@ -234,6 +234,9 @@ class Notifier:
 
         self._third_party_rules = hs.get_module_api_callbacks().third_party_event_rules
 
+        # List of callbacks to be notified when a lock is released
+        self._lock_released_callback: List[Callable[[str, str, str], None]] = []
+
         self.clock = hs.get_clock()
         self.appservice_handler = hs.get_application_service_handler()
         self._pusher_pool = hs.get_pusherpool()
@@ -785,6 +788,19 @@ class Notifier:
         # that any in flight requests can be immediately retried.
         self._federation_client.wake_destination(server)
 
+    def add_lock_released_callback(
+        self, callback: Callable[[str, str, str], None]
+    ) -> None:
+        """Add a function to be called whenever we are notified about a released lock."""
+        self._lock_released_callback.append(callback)
+
+    def notify_lock_released(
+        self, instance_name: str, lock_name: str, lock_key: str
+    ) -> None:
+        """Notify the callbacks that a lock has been released."""
+        for cb in self._lock_released_callback:
+            cb(instance_name, lock_name, lock_key)
+
 
 @attr.s(auto_attribs=True)
 class ReplicationNotifier: