Saga-Pattern Transactions (Rust)

Overview

Golem supports the saga pattern for multi-step operations where each step has a compensation (undo) action. If a step fails, previously completed steps are automatically compensated in reverse order.

All transaction APIs are async. Agent methods using transactions must be async fn.

Defining Operations

Each operation has an execute function and a compensate function. Use sync_operation for synchronous logic:

use golem_rust::sync_operation;

let reserve_inventory = sync_operation(
    |sku: String| {
        // Execute: reserve the item
        let reservation_id = call_inventory_api(&sku)?;
        Ok(reservation_id)
    },
    |sku: String, reservation_id: String| {
        // Compensate: cancel the reservation
        cancel_reservation(&reservation_id)?;
        Ok(())
    },
);

let charge_payment = sync_operation(
    |amount: u64| {
        let charge_id = call_payment_api(amount)?;
        Ok(charge_id)
    },
    |amount: u64, charge_id: String| {
        refund_payment(&charge_id)?;
        Ok(())
    },
);

For async execute/compensate logic, use operation with closures returning Box::pin(async move { ... }):

use golem_rust::operation;

let fetch_data = operation(
    |url: String| Box::pin(async move {
        let response = make_http_request(&url).await?;
        Ok(response)
    }),
    |url: String, _response: String| Box::pin(async move {
        cleanup(&url).await?;
        Ok(())
    }),
);

Fallible Transactions

On failure, compensates completed steps and returns the error. Use boxed to wrap the async closure:

use golem_rust::{fallible_transaction, boxed};

let result = fallible_transaction(|tx| boxed(async move {
    let reservation = tx.execute(reserve_inventory, "SKU-123".to_string()).await?;
    let charge = tx.execute(charge_payment, 4999).await?;
    Ok((reservation, charge))
})).await;

match result {
    Ok((reservation, charge)) => { /* success */ }
    Err(e) => { /* all steps were compensated */ }
}

Infallible Transactions

On failure, compensates completed steps and retries the entire transaction:

use golem_rust::{infallible_transaction, boxed};

let (reservation, charge) = infallible_transaction(|tx| boxed(async move {
    let reservation = tx.execute(reserve_inventory, "SKU-123".to_string()).await;
    let charge = tx.execute(charge_payment, 4999).await;
    (reservation, charge)
})).await;
// Always succeeds eventually

Guidelines

• All transaction functions (fallible_transaction, infallible_transaction) are async — use .await
• Transaction closures must be wrapped with boxed(async move { ... }) (from golem_rust::boxed)
• All tx.execute(...) calls require .await
• Use sync_operation for synchronous execute/compensate logic
• Use operation with Box::pin(async move { ... }) closures for async logic
• Keep compensation logic idempotent — it may be called more than once
• Compensation runs in reverse order of execution
• Use fallible_transaction when failure is an acceptable outcome
• Use infallible_transaction when the operation must eventually succeed