Struct GrpcTaskDelivery 

pub struct GrpcTaskDelivery;

Delivers by pushing a WorkerMessage::ActivityTask onto the worker’s registered stream.

Only two outcomes are reachable here, and that is not an oversight

mpsc::Sender::send().await fails only when the receiver is gone, i.e. the worker’s stream is closed — which is exactly Undeliverable::WorkerUnreachable. A full channel does not error; it applies backpressure and the send waits. So this transport never produces DeliveryFailed.

I record that because my own design note previously claimed a full channel would map to DeliveryFailed. It would — under try_send. Under the send().await this path has always used, that outcome does not exist, and switching to try_send to manufacture it would turn a worker that is merely busy into a failed delivery. DeliveryFailed exists for the blocking transport, which really can fail while its worker is alive.

The intent is asked once, and the backpressure wait is not re-polled

The caller’s intent is checked immediately before the push. If the caller loses its claim during the backpressure wait inside send().await, this arm does not notice: there is no poll boundary to re-ask at, and reaching for one would mean abandoning a send mid-flight.

That is safe, and by two independent mechanisms rather than one:

1. The result cannot be recorded. The completion token is one per pass, minted by the caller and revoked once when the pass places nothing, so a task that lands after its pass withdrew carries an authorization the fences no longer honour.
2. The external effect cannot be duplicated. The task’s idempotency_key is derived from (workflow_id, run_id, activity_id) alone — attempts and execution generations deliberately do not participate (aion-proto/src/worker.rs:143-146) — so a redelivery by whichever pass re-claimed the row carries the same key and is deduplicated at the worker.

The token covers the recording, the idempotency key covers the effect. If either ever stops holding, that is a finding about the fences or the key — not a reason to start polling a send.

Trait Implementations

impl Clone for GrpcTaskDelivery

fn clone(&self) -> GrpcTaskDelivery

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for GrpcTaskDelivery

impl Debug for GrpcTaskDelivery

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for GrpcTaskDelivery

fn default() -> GrpcTaskDelivery

Returns the “default value” for a type.

impl WorkerTaskDelivery for GrpcTaskDelivery

fn deliver<'life0, 'life1, 'life2, 'life3, 'life4, 'async_trait>( &'life0 self, worker: &'life1 WorkerHandle, task: &'life2 ProtoActivityTask, intent: &'life3 SharedDeliveryIntent, accepted: &'life4 dyn DeliveryAccepted, ) -> Pin<Box<dyn Future<Output = TaskDelivery> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait, 'life3: 'async_trait, 'life4: 'async_trait,

Deliver task to worker, awaiting whatever that transport’s notion of delivery is.