Interface ISnapshotStrategy

Namespace: Stratara.Abstractions.EventSourcing

Assembly: Stratara.Abstractions.dll

Decides whether the event-sourcing runtime should write a new snapshot for a stream that has just had events appended. This is the configurable replacement for the framework's formerly hard-coded "snapshot every 50 events, always on" policy.

public interface ISnapshotStrategy

Extension Methods: FieldChangedEventExtensions.ApplyPropertyChanged<TAggregate>(TAggregate, FieldChangedEvent<TAggregate>)

EventStream.ApplyEvents(object, IReadOnlyList<IEvent>)

Remarks

The default implementation registered by AddEventSourcing() snapshots a stream once it has advanced by a fixed number of versions since its last snapshot (50 by default).

To take over the policy — for example to vary the threshold per aggregate type, or to turn snapshots off entirely — register your own singleton implementation of this interface in DI. The framework resolves the last-registered ISnapshotStrategy, so a custom registration wins regardless of whether it runs before or after AddEventSourcing().

Methods

ShouldSnapshot(Type, long, long)

Determines whether a snapshot should be written for the stream described by the arguments.

bool ShouldSnapshot(Type aggregateType, long currentVersion, long lastSnapshotVersion)

Parameters

aggregateType Type: The runtime aggregate type of the stream being evaluated.
currentVersion long: The stream's highest version after the events just appended.
lastSnapshotVersion long: The version of the most recent existing snapshot for the stream, or 0 when the stream has no snapshot yet.

Returns

bool: true to write a fresh snapshot at currentVersion; otherwise false.