Question

Say I have this code:

private void CreateSnapshots(IEnumerable<StreamHead> streams)
{
    foreach (StreamHead head in streams)
    {
        IAggregate aggregate = ???;
        IMemento memento = aggregate.GetSnapshot();

        var snapshot = new Snapshot(head.StreamId, head.SnapshotRevision + 1, memento);

        eventStore.AddSnapshot(snapshot);

        observer.Notify(new SnapshotTaken(head.StreamId, head.HeadRevision));
    }
}

how do I know what aggregate to load for the current stream? I’m also using CommonDomain. Is there something in there?

Thanks

Answer 1

The snapshotting aspect of the EventStore needs a bit of love. I have tried to make the IStoreEvents interface geared toward working with an individual aggregate. I have also tried to ensure that snapshotting does not interfere or get in the way of normal use.

Since the release of v2.0, I have now turned my attention toward v2.1 and I will be able to make a few small API changes related to this. In the meantime, your best option is probably to bypass IStoreEvents altogether when doing snapshotting.

Another alternative is to have the snapshotting code run in-process with your regular code. When an aggregate is loaded the needs a snapshot, you could easily push a reference to that aggregate asynchronously to your snapshotting code. In this way, you don’t actually have to do a load because you already have the aggregate.