Excalibur.EventSourcing.CosmosDb 3.0.0-alpha.208

Excalibur.EventSourcing.CosmosDb

Azure Cosmos DB event store implementation for Excalibur event sourcing.

Features

• Partition-aware event storage using {aggregateType}:{aggregateId} as partition key
• Transactional batch support for atomic event appending
• Change feed integration for event streaming
• Optimistic concurrency with version-based conflict detection
• Auto-provisioning of containers with configurable throughput

Installation

dotnet add package Excalibur.EventSourcing.CosmosDb

Configuration

services.AddCosmosDbEventStore(options =>
{
 options.EventsContainerName = "events";
 options.PartitionKeyPath = "/streamId";
 options.UseTransactionalBatch = true;
 options.MaxBatchSize = 100;
 options.ChangeFeedPollIntervalMs = 1000;
 options.CreateContainerIfNotExists = true;
 options.ContainerThroughput = 400;
});

Or via configuration:

services.AddCosmosDbEventStore(configuration.GetSection("CosmosDbEventStore"));

Usage

The package registers both IEventStore and ICloudNativeEventStore:

public class MyService
{
 private readonly IEventStore _eventStore;

 public MyService(IEventStore eventStore)
 {
 _eventStore = eventStore;
 }

 public async Task AppendEventsAsync(
 string aggregateId,
 IEnumerable<IDomainEvent> events,
 long expectedVersion,
 CancellationToken ct)
 {
 var result = await _eventStore.AppendEventsAsync(
 aggregateId,
 "MyAggregate",
 events.ToList(),
 expectedVersion,
 ct);

 if (!result.Success)
 {
 // Handle concurrency conflict or failure
 }
 }
}

Cloud-Native Features

For partition-aware operations, use ICloudNativeEventStore:

public class CloudNativeService
{
 private readonly ICloudNativeEventStore _eventStore;

 public CloudNativeService(ICloudNativeEventStore eventStore)
 {
 _eventStore = eventStore;
 }

 public async Task LoadWithPartitionAsync(CancellationToken ct)
 {
 var partition = new PartitionKey("MyAggregate", "aggregate-123");
 var result = await _eventStore.LoadEventsAsync(partition, 0, ct);
 // Process events...
 }
}

Change Feed Subscription

Subscribe to event changes for projections or other event handlers:

await using var subscription = await _eventStore.SubscribeToChangesAsync(ct);
await subscription.StartAsync(ct);

await foreach (var change in subscription.ReadChangesAsync(ct))
{
 // Process event change
 Console.WriteLine($"Event: {change.Document?.EventType}");
}

Requirements

• .NET 9.0+
• Azure Cosmos DB account
• Excalibur.Data.CosmosDb for connection management

License

See LICENSE files in repository root.