org.elder.sourcerer.EventSubscriptionPositionSource Maven / Gradle / Ivy
package org.elder.sourcerer;
/**
* Responsible for retrieving the current position of a logical subscription. The event subscription
* position source (if one is provided) is queried when subscriptions are started to know where to
* resume an existing subscription from.
*
* The event subscription position source may also be queried when a subscription is resumed due to
* network disconnects or other intermittent failures.
*
* Implementations may either track progress explicitly, e.g. by periodically storing the current
* position, or implicitly, by deducing the current position from materialized data.
*/
@FunctionalInterface
public interface EventSubscriptionPositionSource {
/**
* Gets the current position to start or resume a subscription from.
*
* @return The numerical stream position / version to start or resume a subscription from,
* exclusive. This would normally be the version of the last event that was successfully handled
* by the subscription. Use null to start the subscription from the beginning.
*/
Integer getSubscriptionPosition();
}