Vulthil.SharedKernel.Outbox

The transactional outbox engine — the message-capture model, the relay processor and background service, the pluggable sinks (IOutboxDispatcher), the commit-time relay signal/gate, and the persistence-agnostic IOutboxStore seam. It has no EF Core dependency; the EF implementation lives in Vulthil.SharedKernel.Outbox.EntityFrameworkCore.

When to use

• You normally consume the outbox transitively. Reference Vulthil.SharedKernel.Infrastructure and call EnableOutboxProcessing() — it hosts this engine and adds the DbContext base + DI wiring.
• Reference this package directly only when you need the EF-free engine contracts — for example a messaging bridge such as Vulthil.Messaging.Outbox, which captures and relays broker messages through IOutboxStore and depends on the engine alone (no EF Core, no infrastructure package).

Pattern

• One OutboxMessages table, one relay; rows are routed by an OutboxDestination discriminator to the registered IOutboxDispatcher, so in-process domain events and broker messages share a single outbox.
• The engine relies on IOutboxStore for both capture (AddOutboxMessage/SaveChangesAsync/IsInTransaction) and the relay batch unit (ProcessBatchAsync); the EF implementation and provider stores supply the transaction and row-locking. AddOutboxEngine registers the engine's own internals.
• Relay spans are emitted on the ActivitySource "Vulthil.SharedKernel.Outbox" (Telemetry.ActivitySourceName), auto-registered with OpenTelemetry by AddOutboxEngine (manual: tracing.AddVulthilOutboxInstrumentation()).
• Relay metrics (counters vulthil.outbox.relayed/vulthil.outbox.failed) are emitted on a Meter (Telemetry.MeterName), auto-registered by AddOutboxEngine when EnableMetrics is on (manual: metrics.AddVulthilOutboxInstrumentation()).
• Opt into a retention sweep via EnableOutboxProcessing(o => o.Retention.Enabled = true) to periodically delete processed and dead-lettered rows older than a window (relational set-based ExecuteDelete; the same sweep covers Cosmos).

See the Outbox Pattern article for the design, the pluggable-sink model, and the commit-time trigger.