Resonate Saga Pattern — Python

Overview

A saga is a long-running transaction split into smaller steps, each with a compensating action. Forward steps run top-to-bottom; on failure, compensations run bottom-to-top to restore consistency. Python's native try/except expresses this cleanly when the durable function uses await ctx.run(...) for each step.

For the TS version's mental model, see resonate-saga-pattern-typescript. The Python expression differs in syntax (try/except instead of try/catch, async def + await instead of function* + yield) and in how compensation lists are collected.

When to use

• Multi-step workflow where intermediate state is visible to other consumers (charge a card → create shipment)
• Each step is idempotent or inexpensive to retry individually
• Compensation logic exists for every committed step
• You need "all or nothing" consistency without a distributed transaction

Don't use when steps are a pure in-memory pipeline (use sequential ctx.run calls without compensation), or when you have access to a single DB transaction that covers all steps.

Basic shape