ResQ.BuildingBlocks.Adapters.Messaging 0.2.0

ResQ.BuildingBlocks.Adapters.Messaging

A broker-agnostic messaging adapter (driven ring) that implements the integration-event ports owned by ResQ.BuildingBlocks.Application and adds the transport, serialization, and consumer machinery. It ships no broker client — the default transport is an in-memory System.Threading.Channels loopback, so a service is publish/consume-capable from minute one and can swap in a real broker later without touching call sites.

Depends only on ResQ.BuildingBlocks.Application + ResQ.BuildingBlocks.Domain.

What's in the box

• Serialization: SystemTextJsonMessageSerializer (IMessageSerializer) — UTF-8 JSON, web defaults, optional custom JsonSerializerOptions.
• Transport contracts: MessageEnvelope (the wire record) and IMessageSource (read / acknowledge / nack).
• Default transport: ChannelMessageBroker — an unbounded channel that is both IIntegrationEventPublisher (write) and IMessageSource (read). Nacks re-enqueue.
• Typed dispatch: IIntegrationEventHandler<TEvent> + IntegrationEventDispatcher — resolves the CLR type via DictionaryIntegrationEventTypeRegistry, deserializes, and fans out to every handler in the current scope (reflection cached per type).
• Consumer: MessageConsumerService (BackgroundService) — concurrency-bounded (SemaphoreSlim), idempotency short-circuit, a Polly ResiliencePipeline retry built from RetryOptions, dead-letter on exhaustion, and in-flight draining on shutdown. Configured via ConsumerOptions.
• Reliability: RetryOptions, IDeadLetterSink (+ LoggingDeadLetterSink default, NullDeadLetterSink).
• Opt-outs: NullIdempotencyStore (always "not processed"), NullIntegrationEventPublisher (discards).

Wiring

services.AddResqMessaging(
    b => b.UseInMemory(),          // publisher + source = ChannelMessageBroker
    typeof(SomethingHappened).Assembly);  // scans IntegrationEvent subtypes + handlers

AddResqMessaging registers the serializer, a registry populated from the scanned assemblies, the dispatcher, the discovered IIntegrationEventHandler<> implementations (scoped), and the default NullIdempotencyStore + LoggingDeadLetterSink. Swap components with UsePublisher<T>(), AddMessageSource<TSource>() (or AddKeyedMessageSource<TSource>(key) to bind distinct sources to distinct consumers), and UseDeadLetterSink<T>().

To run a consumer, subclass MessageConsumerService and register it as a hosted service; the subclass name is the idempotency handler key. A durable idempotency store (e.g. the EF inbox from Adapters.Persistence) or dead-letter sink registered elsewhere is honored automatically.

The dead-letter / retry-with-jitter / idempotency stack is exercised through the in-memory transport until a real broker adapter (e.g. Kafka) lands.

Apache-2.0 · part of resq-software/dotnet.