Saga Pattern: Trip Booking

A trip booking workflow that demonstrates the saga pattern with automatic compensation. Books a flight, hotel, and car rental — if the car rental fails, it automatically cancels the hotel and flight in reverse order.

No saga framework. No compensation tables. Just a generator function with try/catch.

What This Demonstrates

• The saga pattern: multi-step distributed transaction with rollback
• Durable compensation: each cancellation step is checkpointed — if the process crashes mid-compensation, it resumes where it left off
• Crash recovery: kill the process at any point and restart — it picks up from the last checkpoint
• Selective retry policy: fail-fast on the car rental to trigger compensation immediately

Prerequisites

• Bun v1.0+

No external services required. Resonate runs in embedded mode.

Setup

git clone https://github.com/resonatehq-examples/example-saga-booking-ts
cd example-saga-booking-ts
bun install

Run It

Happy path — all bookings succeed:

bun start

=== Resonate Saga Pattern: Trip Booking ===
Mode: SUCCESS (all bookings will succeed)
  [flight]  Booking flight for trip trip-1234567890...
  [flight]  Flight booked: FL-ABC123
  [hotel]   Booking hotel for trip trip-1234567890...
  [hotel]   Hotel booked: HT-DEF456
  [car]     Booking car rental for trip trip-1234567890...
  [car]     Car rental booked: CR-GHI789

=== Result ===
{
  "status": "success",
  "tripId": "trip-1234567890",
  "flightId": "FL-ABC123",
  "hotelId": "HT-DEF456",
  "carId": "CR-GHI789"
}

Failure path — car rental fails, hotel and flight are cancelled:

bun start:fail

=== Resonate Saga Pattern: Trip Booking ===
Mode: FAILURE (car rental will fail, triggering compensation)
  [flight]  Booking flight for trip trip-1234567890...
  [flight]  Flight booked: FL-ABC123
  [hotel]   Booking hotel for trip trip-1234567890...
  [hotel]   Hotel booked: HT-DEF456
  [car]     Booking car rental for trip trip-1234567890...
  [hotel]   Cancelling hotel HT-DEF456...
  [hotel]   Hotel cancelled: HT-DEF456
  [flight]  Cancelling flight FL-ABC123...
  [flight]  Flight cancelled: FL-ABC123

=== Result ===
{
  "status": "failed",
  "tripId": "trip-1234567890",
  "error": "Car rental unavailable: no cars at this location",
  "compensated": ["hotel", "flight"]
}

What to Observe

1. Compensation runs in reverse order: hotel cancels before flight (last-in, first-out)
2. Each step is a checkpoint: open src/workflow.ts and add process.exit(1) after any yield* — restart the process and it resumes from that point
3. Crash mid-compensation: if you crash during hotel cancellation, it will retry the hotel cancellation on restart (not restart the whole saga)

The Code

The entire saga is 25 lines of business logic in src/workflow.ts:

export function* bookTrip(ctx: Context, tripId: string, shouldFail: boolean) {
  let flightId: string | undefined;
  let hotelId: string | undefined;

  try {
    flightId = yield* ctx.run(bookFlight, tripId);
    hotelId  = yield* ctx.run(bookHotel, tripId);
    const carId = yield* ctx.run(bookCarRental, tripId, shouldFail,
                                  ctx.options({ retryPolicy: noRetry }));

    return { status: "success", tripId, flightId, hotelId, carId };
  } catch (error) {
    // Compensate in reverse order
    if (hotelId)  yield* ctx.run(cancelHotel, tripId, hotelId);
    if (flightId) yield* ctx.run(cancelFlight, tripId, flightId);

    return { status: "failed", tripId, error: (error as Error).message, compensated };
  }
}

Each yield* is a durable checkpoint. That's it.

File Structure

example-saga-booking-ts/
├── src/
│   ├── index.ts       Entry point — Resonate setup and saga invocation
│   ├── workflow.ts    The saga: bookTrip with compensation logic
│   └── services.ts    Simulated booking APIs (flight, hotel, car rental)
├── package.json
└── tsconfig.json

Lines of code: ~200 total (including comments and blank lines), ~80 lines of actual logic. The bookTrip saga itself is 30 lines.

Learn More

• Resonate documentation