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EventStore

README.md

Event store

An event is a collection of data that describes a change in state, e.g. an order has been placed.
An event store is just a database that stores events. This is a pretty simple idea with some very powerful implications.

The package NBB.EventStore.Abstractions contains IEventStore a lightweight abstraction over any EventStore client. It is meant to be consumed only by infrastructure packages in order to decouple from any EventStore implementation.

The package NBB.EventStore offers EventStore, a modest implementation of the concept.

Event repositories

The EventStore delegates persistence responsibilities to the IEventRepository implementations in order to decouple from any possible implementation.

ADO.NET

The package NBB.EventStore.AdoNet offers an ADO.NET based implementation for IEventRepository.

The package NBB.EventStore.AdoNet.MultiTenancy offers an ADO.NET based implementation for IEventRepository with multi-tenancy support.

The package NBB.EventStore.AdoNet.Migrations offers a migrations API for AdoNetEventRepository.

In-memory

The package NBB.EventStore.InMemory offers an in-process implementation for IEventRepository.

Registration

Example: register the event store using ADO.NET event repository and JSON serialization:

services.AddEventStore(b =>
{
    b.UseNewtownsoftJson(new SingleValueObjectConverter());
    b.UseAdoNetEventRepository(o => o.FromConfiguration());
});

When using FromConfiguration, the connection string used by the ADO.net repository is configured in section EventStore.NBB.ConnectionString

{
  ...
  "EventStore": {
    "NBB": {
      "ConnectionString": "..."
    }
  }
}

Concurrency model

The event store uses the concurrency model defined at the IEventRepository level (at the storage level).

The EfEventRepository and AdoNetEventRepository offers optimistic concurrency based on the event's SequenceNumber.

If two threads or processes want to save to events with the same sequence number to same stream of events, the last will fail with a ConcurrencyException.

Snapshotting

The package NBB.EventStore.Abstractions contains ISnapshotStore a lightweight abstraction for any snapshot store client.

The SnapshotStore delegates persistence responsibilities to the ISnapshotRepository implementations in order to decouple from any possible implementation.

The package NBB.EventStore.AdoNet offers an Ado.Net based implementation for ISnapshotRepository.

Effects

The package NBB.EventStore.Effects contains event-store side effects and handlers for the NBB effects infrastructure