Crate email_transport_restate 

Restate ingress transport for outbound email delivery.

This crate implements email_transport::Transport on top of a Restate Email.send ingress invocation, so the same application code can hand a message to a durable queue instead of a provider. The wire contract it submits is owned by restate-email; the worker side of the contract lives there as well. Depending on this crate never pulls in the Restate SDK.

RestateTransport follows a send as far as its InvocationMode says: in the default InvocationMode::Queued mode it returns once Restate has durably accepted the invocation and reports the invocation id; in InvocationMode::Sent mode it waits for the worker and returns the worker’s provider report. A per-send RestateSendOptions overrides the configured mode and may delay a queued invocation.

Quick start

use email_message::{Address, Body, Message};
use email_transport::{SendOptions, Transport};
use email_transport_restate::{RestateTransport, TransportKey};

let message = Message::builder(Body::text("Welcome"))
    .from_mailbox("sender@example.com".parse()?)
    .to(vec![Address::Mailbox("recipient@example.com".parse()?)])
    .build_outbound()?;

let transport = RestateTransport::new(
    TransportKey::new("transactional")?,
    "http://127.0.0.1:8080".parse()?,
);
transport.send(&message, &SendOptions::default()).await?;

Authentication

Restate Cloud ingress requires an API key as a bearer token; configure it with RestateTransportBuilder::bearer_token. Self-hosted Restate has no built-in ingress authentication; a fronting reverse proxy that expects the same Authorization: Bearer header is covered by the same setter, and any other header scheme can be attached to a custom reqwest::Client passed to RestateTransportBuilder::client.

Features

The default feature set enables the default reqwest client stack. Disable default features to choose reqwest’s transport/TLS features explicitly.

• schemars: forwards JSON Schema derivation to the re-exported restate-email queue payload types.

Example programs

• invoke_local_worker invokes Email.send through Restate ingress with a raw HTTP client and waits for the response.
• direct_or_restate sends through the same application function using either a direct provider transport or RestateTransport.

Structs

RestateSendOptions

Restate-specific options for a single send attempt.

RestateTransport

Email transport backed by a Restate Email.send ingress invocation.

RestateTransportBuilder

Builder for RestateTransport.

SendRequest

Queue payload consumed by Email.send.

SendRequestSeed

Registry-driven deserializer for SendRequest.

SendResponse

Wire-stable response shape returned by the Restate Email.send handler.

TransportKey

Configured transport key (e.g. "primary", "fallback").

Enums

InvocationMode

How far a Restate-backed send is followed before it returns.