Channels

A subscription's channel reports its address, terminus, credit and settle mode; a publish channel reports the address its sender targets.

A subscription's extension has four fields, read from its AmqpAddress. address is the node the receiver attaches to. capability is the terminus it asks for, queue or topic. An AmqpAddress::raw address asks for none, so its channel has no capability. credit is the link credit, 256 unless the descriptor sets credit. settleMode is at-least-once, or at-most-once for a descriptor with Settle::AtMostOnce.

A channel the service publishes to carries one field, address: the node the sender attaches its target to. That is a reply destination, the name of an Out slot, or a dead-letter address. A reply routed per request has no fixed address on its channel, and the extension still names the destination its mount site declared.

Example

The channel orders reports a queue with a credit of 64, events a topic settled at most once, and /queues/audit no terminus. The channels receipts, orders.dead and ledger report the address each sender targets.

Macros

examples/amqp_asyncapi.rs

#[subscriber(AmqpAddress::queue("orders").credit(nonzero!(64)), reply("receipts"))]
async fn confirm(order: &Order) -> Receipt {
    Receipt { order_id: order.id }
}

#[subscriber(AmqpAddress::topic("events").settle(Settle::AtMostOnce))]
async fn watch(order: &Order) -> HandlerOutcome {
    tracing::info!(order.id, "event seen");
    HandlerOutcome::ack()
}

#[subscriber(AmqpAddress::raw("/queues/audit"))]
async fn audit(order: &Order) -> HandlerOutcome {
    tracing::info!(order.id, "audited");
    HandlerOutcome::ack()
}

Manual

examples/manual/amqp_asyncapi.rs

/// The queue `orders`, with a credit of 64.
fn orders() -> AmqpAddress {
    AmqpAddress::queue("orders").credit(nonzero!(64))
}

/// The topic `events`, settled on receipt.
fn events() -> AmqpAddress {
    AmqpAddress::topic("events").settle(Settle::AtMostOnce)
}

/// The address `/queues/audit`, sent as written.
fn audit_queue() -> AmqpAddress {
    AmqpAddress::raw("/queues/audit")
}