Outbox AMQP Dispatch

ID: dispatch.outbox.amqp
Name: Outbox AMQP dispatch
Maturity: GA
Summary: Publish leased outbox envelopes to RabbitMQ with LiteBus contract headers through TransportOutboxDispatcher.

What It Does

AddAmqpTransport(...) registers AmqpTransportModule once at the root. UseAmqpDispatch(configure) on OutboxModuleBuilder registers TransportOutboxDispatchModule as a feature bridge to that transport. After domain logic enqueues events to outbox storage, the processor publishes to the configured exchange when rows are leased.

Route resolution prefers envelope Topic, then custom resolver, then contract name. Headers carry contract identity and trace context for downstream ingress.

Packages

Package	Role
`LiteBus.Outbox.Dispatch.Amqp`	Registration glue
`LiteBus.Outbox.Dispatch`	Shared transport outbox dispatcher
`LiteBus.Transport.Amqp`	RabbitMQ client

Requires

dispatch.transport-core
transport.amqp
durable-core.outbox

Invariants

Default hook failure policy is CompleteDespiteHookFailure for transport outbox modules.
At-least-once publication: crash after broker ack but before terminal persist can duplicate messages.
Downstream consumers must deduplicate (message id, idempotency header, or business keys).

Non-Goals

Does not subscribe to queues.
Does not guarantee transactional outbox with broker (two-phase ack not built in).

Public Surface

services.AddLiteBus(litebus =>
{
    litebus.AddAmqpTransport(new AmqpConnectionOptions
    {
        HostName = "localhost",
        Port = 5672,
        UserName = "guest",
        Password = "guest"
    });

    litebus.AddOutbox(outbox =>
    {
        outbox.EnableOutboxProcessor();
        outbox.UseAmqpDispatch(
            options =>
            {
                options.DefaultDestination = "events.exchange";
                options.ResolveRoute = envelope => envelope.Topic ?? envelope.ContractName;
                options.Persistent = true;
            });
    });
});

API	Role
`OutboxModuleBuilder.UseAmqpDispatch(Action<TransportOutboxDispatcherOptions>)`	Registers outbox transport dispatcher that requires the root AMQP transport
`TransportOutboxDispatchModule.DefaultHookFailurePolicy`	Defaults to `CompleteDespiteHookFailure`
`TransportOutboxDispatcher.DispatchAsync(OutboxEnvelope, CancellationToken)`	Publishes outbox envelope to broker with canonical headers

TransportOutboxDispatcherOptions:

Property	Default	Role
`DefaultDestination`	`""`	Exchange name
`ContentType`	`application/json`	Outgoing MIME content type
`Persistent`	`true`	Durable message flag
`Mandatory`	`false`	Fail publish when unroutable
`ResolveRoute`	`null`	Route selector after topic fallback
`ValidatePayloadBeforeDispatch`	`false`	Deserialize payload before publish for validation

Outbox route order is tenant strategy, then envelope Topic, then ResolveRoute, then contract name.

AmqpConnectionOptions:

Property	Default	Role
`Uri`	`null`	Full AMQP URI, overrides host/port/credentials when set
`HostName`	`localhost`	Broker host
`Port`	`5672`	Broker port
`VirtualHost`	`/`	AMQP virtual host
`UserName` / `Password`	`guest` / `guest`	Broker credentials
`ClientProvidedName`	`null`	Connection name shown in broker UI
`AutomaticRecoveryEnabled`	`true`	Enables reconnect
`NetworkRecoveryInterval`	`00:00:05`	Delay between reconnect attempts
`CircuitBreaker`	configured object	Separate connection and per-exchange publisher breaker thresholds

Observability

Signal	Detail
`send {destination}`	Exchange, RabbitMQ routing key, and envelope id on the AMQP send path
`litebus.transport.circuit_breaker.*`	Broker tag `amqp` on shared transport meter
`litebus.outbox.processor.published` / `failed` / `dead_lettered`	After dispatch and terminal persist
`litebus.outbox.processor.dispatch_duration`	Includes AMQP publish latency

Test method	Project
`UseAmqpDispatch_WithAmqpTransportModule_ShouldRegisterTransportOutboxDispatcher`	`LiteBus.Durable.IntegrationTests` (`Dispatch/Outbox/Amqp/`)
`OutboxDispatchExtensions_ShouldRegisterTransportDispatcher`	`LiteBus.Durable.IntegrationTests` (`Registration/`)
`ProcessPendingAsync_ShouldPublishEnvelopeToAmqpQueue`	`LiteBus.Durable.IntegrationTests` (`Dispatch/Outbox/Amqp/`)
`ProcessPendingAsync_WhenTopicMissing_ShouldUseContractNameAsRoutingKey`	`LiteBus.Durable.IntegrationTests` (`Dispatch/Outbox/Amqp/`)
`ProcessPendingAsync_ShouldPublishToAmqpAndMarkPostgreSqlEnvelopePublished`	`LiteBus.Durable.IntegrationTests` (`Dispatch/Outbox/Amqp/`)

Untested

After-dispatch hook failure path with CompleteDespiteHookFailure under live AMQP.
Outbox dispatch failure and circuit breaker behavior for AMQP dispatch projects.
Route override via tenant strategy in AMQP-specific coverage.

Out-of-Scope

Subscribing to or consuming AMQP queues
Two-phase transactional outbox with broker acknowledgment persisted before terminal store state