restate-email

Restate email worker contracts and service adapter.

Scope contract

Defines a serializable send-email request payload around email_message::Message.
Dispatches messages through keyed email_transport::Transport registrations.
Exposes the payload as a Restate Email.send service handler.
Maps worker and transport failures into Restate retry semantics.

SendRequest: transport reference plus message payload and raw send-time options.
RawSendOptions: wire-safe send-time metadata, including envelope overrides, timeout, idempotency key, correlation id, and provider-specific transport_options staged as serde-value values.
TransportResolver: resolves a transport key into a configured Transport instance.
StaticTransportRegistry: small owned registry for common fixed-key worker setups.
ServiceImpl: concrete Restate service wrapper over a TransportResolver and provider-option registry. The handler hydrates RawSendOptions into email_transport::SendOptions and dispatches inside a named Restate ctx.run journaled action.
SendResponse: serializable response wrapper containing the transport SendReport.

schemars: derives JSON Schema for public queue payload types such as SendRequest, reusing the schema from email-message and email-transport.
resend: enables email-kit's Resend provider-option deserialization for queued transport_options entries.

Retryable transport failures remain retryable Restate handler failures.
Unknown transport keys, validation errors, and other permanent failures are mapped to terminal Restate errors.

Run the local example server: cargo run -p restate-email --example restate_email_worker
The example starts HttpServer::new(service.endpoint()) on 127.0.0.1:9080.
It prints a sample SendRequest JSON payload and the Restate ingress handler path POST /Email/send.
The raw SDK endpoint on 127.0.0.1:9080 is meant to be registered behind Restate; it is not a plain JSON handler by itself.
Invoke the local example server: cargo run -p restate-email --example invoke_local_worker
The client example posts a sample SendRequest to http://127.0.0.1:8080/Email/send by default, assuming a local Restate ingress.
Override the target with RESTATE_INGRESS_URL=http://host:port if needed.
Run the Resend-backed example server: cargo run -p restate-email --example restate_resend_worker
The Resend example expects RESEND_API_KEY, RESEND_FROM, and RESEND_TO and starts on 127.0.0.1:9081.

Run tests: cargo test -p restate-email
Run the Dagger test wrapper: dagger call test
Run the Dagger Restate ingress e2e: dagger call restate-ingress
The Rust test suite covers raw SDK protocol handling without starting Docker. Restate ingress e2e coverage runs through the Dagger Restate service module so cargo test remains deterministic.