resonate-basic-durable-world-usage-rust

Resonate Basic Durable World Usage — Rust

SDK note. The Resonate Rust SDK (resonate-sdk v0.6.0, published on crates.io) is in active development; APIs may change between releases. Verify against the current SDK source before relying on any specific shape.

Overview

Durable functions in Rust are async functions decorated with #[resonate::function]. The macro wraps your function in Resonate's durable-execution machinery — every successful ctx.run / ctx.rpc / ctx.sleep is a checkpoint, and the function resumes from the last checkpoint on process restart.

This skill covers the Context API surface used inside those functions. The ephemeral-world counterpart (registration, top-level invocation, promises) lives in resonate-basic-ephemeral-world-usage-rust.

The contract

• Attribute macro: #[resonate::function] (or #[resonate::function(name = "alias")])
• Async function: async fn — tokio is the default runtime
• Return type: Result<T> (aliased from resonate::error::Result) — use ? for propagation
• First parameter inferred kind:

First param	Kind	Capabilities
&Context	Workflow	ctx.run, ctx.rpc, ctx.sleep, .spawn() parallelism, context accessors
&Info	Leaf with metadata	Read-only access to info.id(), info.parent_id(), etc.
value types (String, MyStruct)	Pure leaf	No context; stateless computation

Minimal workflow shape:

use resonate::prelude::*;

#[resonate::function]
async fn process_order(ctx: &Context, order_id: String) -> Result<String> {
    let order = ctx.run(load_order, order_id.clone()).await?;
    let charge = ctx.rpc::<String>("charge_card", order.clone()).await?;
    Ok(format!("order={} charge={}", order, charge))
}

#[resonate::function]
async fn load_order(order_id: String) -> Result<String> {
    Ok(format!("order-{}", order_id))
}

If this workflow crashes after load_order but before rpc("charge_card"), it resumes at the rpc call on restart — load_order is NOT re-executed; its stored result is returned.