Struct SubscriptionBuilder 

pub struct SubscriptionBuilder<S, P, SS>
where
    S: EventStore,
    P: ProjectionFilters,
{ /* private fields */ }

Builder for configuring and starting a subscription.

Created via Repository::subscribe(). Use on_update() to register callbacks, then call start() to begin processing events.

Implementations

impl<S, P, SS> SubscriptionBuilder<S, P, SS>

where S: SubscribableStore + Clone + Send + Sync + 'static, S::Position: Ord + Send + Sync, S::Data: Send, S::Metadata: Send + Sync, P: Projection + ProjectionFilters<Id = S::Id, Metadata = S::Metadata> + Serialize + DeserializeOwned + Send + Sync + 'static, P::InstanceId: Clone + Send + Sync + 'static, P::Metadata: Send, SS: SnapshotStore<P::InstanceId, Position = S::Position> + Send + Sync + 'static,

pub fn on_update<F>(self, callback: F) -> Self

where F: Fn(&P) + Send + Sync + 'static,

Register a callback invoked after each event is applied.

Callbacks must complete quickly. Long-running work should be dispatched to a separate task via a channel. Blocking the callback stalls the subscription loop and delays event processing.

pub async fn start( self, ) -> Result<SubscriptionHandle<S::Error>, SubscriptionError<S::Error>>

Start the subscription.

This method returns only after catch-up completes.

Spawns a background task that:

1. Loads the most recent snapshot (if available)
2. Subscribes to the event stream from the snapshot position
3. Replays historical events (catch-up phase)
4. Waits until catch-up is complete
5. Continues processing live events and firing on_update

Errors

Returns an error if the initial snapshot load or stream setup fails.