saga

Saga Pattern — Durable Task SDK (Python)

Python | Durable Task SDK

Description

Demonstrates the Saga pattern (compensating transactions) using the Durable Task SDK for Python. A travel booking orchestration reserves a flight, hotel, and rental car in sequence. If any step fails, previously completed steps are rolled back using compensating actions.

This pattern is useful for:

• Distributed transactions across multiple services
• Booking systems where all-or-nothing semantics are required
• Any multi-step process requiring rollback on failure

Prerequisites

1. Python 3.10+
2. Docker (for the emulator)

Quick Run

1. Start the Durable Task Scheduler emulator:

   docker run -d -p 8080:8080 -p 8082:8082 mcr.microsoft.com/dts/dts-emulator:latest

2. Install dependencies:

   pip install durabletask

3. Start the worker (in one terminal):

   python worker.py

4. Run the client (in another terminal):

   python client.py

5. View in the dashboard: http://localhost:8082

How It Works

1. The orchestration attempts to book a flight, hotel, and car in sequence
2. Each booking activity returns a confirmation ID on success
3. If any step fails (e.g., no cars available), the orchestration enters compensation mode
4. Compensation runs in reverse order — cancelling the hotel, then the flight
5. The orchestration returns either a successful booking or a failure with details of what was rolled back

Learn More

• Saga Pattern
• Durable Task Scheduler Documentation