LineTen.Messaging.Abstractions 2.0.112

LineTen.Messaging.Abstractions

Contracts for LineTen messaging v3. Zero dependencies. Implementations live in LineTen.Messaging.Bus.AzureServiceBus and LineTen.Messaging.Bus.InMemory; registration lives in LineTen.Messaging.DependencyInjection.

Contents

• IMessageBus — marker interface; declare one type per bus.
• IPublisher<TBus> — PublishAsync<T>(message, ct) and PublishAsync<T>(message, PublishOptions, ct).
• PublishOptions — optional CorrelationId and application properties for a publish.
• IPerformer<T> — PerformAsync(T message, IMessageContext context, CancellationToken).
• IDeadLetterPerformer<T> — DeadLetterPerformAsync(T message, DeadLetterContext context, CancellationToken).
• IMessageContext — per-delivery metadata handed to a performer.
• DeadLetterContext — metadata for a dead-lettered message.
• FilterBuilder / FilterExpression — subscription filter DSL compiled by each transport.
• SubscriptionNamer — deterministic subscription naming (Compute(serviceName, topic, messageTypeFqn, filterCanonicalForm)).
• Transport seam (IBrokerTransport, IBrokerPublisher, IBrokerSubscription, IBrokerAdministration) for transport implementers.
• Retry contract (IRetryPolicy, TransientExceptionAttribute, PermanentExceptionAttribute), health contract, telemetry constants.

IMessageContext

MessageId and CorrelationId are different values. A reply has its own MessageId; it carries the request's CorrelationId.

DeadLetterContext

Positional record: Reason, ErrorDescription, Source, DeliveryCount, OriginalEnqueuedAtUtc, DeadLetteredAtUtc, Properties, CorrelationId. CorrelationId is the original message's correlation id, Guid.Empty when it carried none.

Correlation

Resolved at publish time, in order: explicit PublishOptions.CorrelationId; the correlation id of the message being performed, when publishing inside a performer; the ambient W3C trace id; Guid.Empty.

Request/response over a shared response topic:

1. Requester generates requestId, records it in a store shared across its instances, publishes with new PublishOptions(requestId).
2. The responding performer publishes its reply without setting a correlation id. The reply inherits requestId.
3. The requester's reply performer reads context.CorrelationId and looks it up in the shared store. Competing consumers mean any instance may receive the reply; do not use an in-memory pending map.

Version notes

2.0.112

• Added IMessageContext.CorrelationId.
• Added DeadLetterContext.CorrelationId as the eighth positional parameter. Code that constructs DeadLetterContext directly must supply it. Consumers that only implement IPerformer<T> or IDeadLetterPerformer<T> are unaffected.
• Both transports populate the value from the received message. Dead-lettering preserves it.

Documentation

docs/adr/0009-publish-properties-and-correlation.md and docs/adr/0011-consume-side-correlation-exposure.md in the lineten/core-csharp-nuget repository.