Orleans.EventSourcing.Snapshot

Snapshot storage provider for orleans event sourcing

This provider stores grain state snapshots and the event sequence, using a standard storage provider that can be configured independently.

Usage

Install from nuget: dotnet add package Orleans.EventSourcing.Snapshot

Add this provider to SiloBuilder:

builder.AddSnapshotStorageBasedLogConsistencyProviderAsDefault((op, name) => 
{
    // Take snapshot every five events
    op.SnapshotStrategy = strategyInfo => strategyInfo.CurrentConfirmedVersion - strategyInfo.SnapshotVersion >= 5;
    op.UseIndependentEventStorage = true;

    // Should configure independent event storage when set UseIndependentEventStorage true
    op.ConfigureIndependentEventStorage = (services, name) =>
    {
        services.AddSingleton<IGrainEventStorage, SampleIndependentEventStorage>();
    };
});

if you set UseIndependentEventStorage false, This provider use grain storage to store the snapshot and event sequence. Otherwise, This provider use grain storage to store the snapshot state, And use independent event storage that you configurated to store the event sequence. How to configurate the independent event store you can see the code above.

To use the independent event store, you need implement IGrainEventStorage interface:

public interface IGrainEventStorage
{
    Task SaveEvents<TEvent>(string grainTypeName, GrainReference grainReference, IEnumerable<TEvent> events, int expectedVersion);

    Task<List<TEvent>> ReadEvents<TEvent>(string grainTypeName, GrainReference grainReference, int start, int count);

    Task<int> EventsCount(string grainTypeName, GrainReference grainReference);
}

This provider does support RetrieveConfirmedEvents. All events are always available, And where the event keep in denpend on your configuration.

Use case detail you can see the sample project.