f more comments

Author: TheBlueMatt

lightning/src/util/persist.rs

@@ -1085,6 +1085,10 @@ where
 			if persist_update {
 				let monitor_key = monitor_name.to_string();
 				let update_name = UpdateName::from(update.update_id);
+				// Note that this is NOT an async function, but rather calls the *sync* KVStore
+				// write method, allowing it to do its queueing immediately, and then return a
+				// future for the completion of the write. This ensures monitor persistence
+				// ordering is preserved.
 				res_a = Some(self.kv_store.write(
 					CHANNEL_MONITOR_UPDATE_PERSISTENCE_PRIMARY_NAMESPACE,
 					monitor_key.as_str(),
@@ -1093,6 +1097,10 @@ where
 				));
 			} else {
 				// We could write this update, but it meets criteria of our design that calls for a full monitor write.
+				// Note that this is NOT an async function, but rather calls the *sync* KVStore
+				// write method, allowing it to do its queueing immediately, and then return a
+				// future for the completion of the write. This ensures monitor persistence
+				// ordering is preserved. This, thus, must happen before any await we do below.
 				let write_fut = self.persist_new_channel(monitor_name, monitor);
 				let latest_update_id = monitor.get_latest_update_id();
 
@@ -1120,6 +1128,9 @@ where
 			res_c = Some(self.persist_new_channel(monitor_name, monitor));
 		}
 		async move {
+			// Complete any pending future(s). Note that to keep one return type we have to end
+			// with a single async move block that we return, rather than trying to return the
+			// individual futures themselves.
 			if let Some(a) = res_a {
 				a.await?;
 			}