Typed extractors · Consumer

Receive message metadata, DI services, local state, and payload through handler parameters.

Extractors turn framework-owned delivery state into the Rust values a handler requests. Metadata and services are obtained without consuming the body; a payload-owning extractor, if present, must be the final parameter.

Metadata and payload order#

Use the following method in place of the first application's method inside #[queue_service] impl OrderWorker. DeliveryContext and RetryCount do not consume the body; Json<OrderCreated> resolves last. Import the types from lilyrs::queue.

#[queue("orders.created", version = 1, content = "json")]
async fn created(
    &self,
    context: lilyrs::queue::DeliveryContext,
    _retry: lilyrs::queue::RetryCount,
    Json(event): Json<OrderCreated>,
) -> Result<(), QueueHandlerError> {
    let _event_id = context.event_id();
    println!("{}", event.order_id);
    Ok(())
}

Parts extractors run in declaration order. If one rejects, later extractors and the handler are not called; the entered middleware prefix follows normal error unwinding. A handler supports at most 16 extractors and one terminal payload. A type's trait implementation determines its role, rather than whether its name happens to be Json.

Metadata, services, and local state#

Extractor	Value provided
`DeliveryContext`	Queue/exchange/routing, event, schema, content, retry, and redelivery metadata
`EventId`, `SchemaVersion`, `ContentKind`	One field from the contract
`RetryCount`, `Redelivered`	Framework retry count and the separate broker redelivery flag
`DeliveryHeaders`, `DeliveryProperties`	Bounded headers and allowlisted AMQP properties
`DeliveryCancellation`, `DeliveryDeadline`	Read-only execution signal and normal pipeline cutoff
`Service<T>`	DI service resolved through the active delivery scope
`Local<T>`, `Option<Local<T>>`	Typed delivery-local state supplied by an earlier stage

These values carry neither a broker channel nor ACK authority. Receiving a reply_to property does not create an automatic request/reply service. DeliveryCancellation and DeliveryDeadline provide read-only access to framework execution control; your application explicitly connects them to other subsystem contexts.

Choose a payload extractor#

Extractor	Content contract	Behavior
`Json<T>`	`json`	`DeserializeOwned + Send`; malformed JSON is permanent failure
`TextPayload`	`text`	Owned UTF-8 `String`; invalid encoding is permanent failure
`BinaryPayload`	`binary`	Bounded body bytes
`RawDelivery`	A valid explicit content token	Body and metadata; not an ACK/NACK object
Custom `FromDelivery`	Custom contract	Application decoder with sole body authority

Body authority is consumed once. Combining Json<T> and RawDelivery in one method, or placing metadata after the payload, is invalid. Choosing raw body access does not remove envelope validation or transport size bounds.

Optional values and rejection#

Option<E> applies only when E implements OptionalFromDeliveryParts. Option<Local<T>> can represent an absent local value as None; Option<Service<T>> or Option<Json<T>> is not a general mechanism for ignoring errors. A missing required Local<T> produces a retryable error.

Use FromDeliveryParts to build custom values from metadata, DI, or local state, and FromDelivery for body decoding. Deserializing JSON into a Rust type is separate from validating business data.