Retry

The attempt cap and the dead-letter destination of a registration appear on its receive operation as the x-ruststream-retry extension.

max_attempts(n) is maxAttempts, and dead_letter(name) is deadLetter. AsyncAPI has a field for neither: a binding models a dead-letter queue only for SQS and SNS, and nothing models an attempt cap. So the document carries them as an extension of the operation. The dead-letter destination is a channel of its own, with a send operation, since the registration publishes there. Retry copies sent to a named destination add retryDestination, with its channel (see Retry slot). Copies that return to the subscription's own address add nothing: that channel is already in the document. A registration that declares none of this has no extension. The example runs with cargo test --example asyncapi_reports --features macros,memory,asyncapi.

Example

Macros

examples/asyncapi_reports.rs

fn app() -> impl App {
    RustStream::new(AppInfo::new("orders", "0.1.0")).with_broker(MemoryBroker::new(), |b| {
        b.include(confirm);
        b.include(accept).out(Tenants, Publish).build();
        b.include(ship);
        // The cap and the dead-letter destination reach the document with the registration.
        b.include(charge)
            .max_attempts(nonzero!(3u32))
            .dead_letter("payments.dead");
    })
}

Manual

examples/manual/asyncapi_reports.rs

fn app() -> impl App {
    RustStream::new(AppInfo::new("orders", "0.1.0")).with_broker(MemoryBroker::new(), |b| {
        b.include(
            subscriber("order-requests", Confirm)
                .describe("Confirms every order request.")
                .reply()
                .to("confirmations")
                .build(),
        );
        b.include(subscriber("orders", Accept).build())
            .out(Tenants, Publish)
            .build();
        b.include(subscriber("shipments", Ship).build());
        // The cap and the dead-letter destination reach the document with the registration.
        b.include(subscriber("payments", Charge).build())
            .max_attempts(nonzero!(3u32))
            .dead_letter("payments.dead");
    })
}