We use a driver to create bookings silently.
On that driver, we would like to display the current state of the bookings (confirmed/on going/cancelled /completed).
We were planning to make a request based on a timer but would like to know if there is some subscription based mechanism to get updates from the booking's state.
To get updates on state changes of the core booking objects (ReservationInstances) you can subscribe on the ResourceManagerEventMessage event.
The property ResourceManagerEventMessage#UpdatedReservationInstances : List<ReservationInstance> will contain the updated reservation instances.
Any update of any reservation instance on the cluster will come in through this event subscription.
You can also use filtered subscriptions to subscribe only on certain reservation instances by using a filter of type "SubscriptionFilter<ResourceManagerEventMessage, ReservationInstance>".