resonate-basic-ephemeral-world-usage-python

Resonate Basic Ephemeral World Usage — Python

Overview

The ephemeral world is anywhere your Python process starts: a main(), a FastAPI route, an HTTP handler, a script, a worker entry point. You use the Resonate class to register durable functions and invoke them. Once an invocation starts, it crosses into the durable world and Resonate guarantees its completion — retries on failure, resumes after crashes, continues across restarts.

This skill covers the Client API surface. The Durable World (Context APIs) lives in resonate-basic-durable-world-usage-python.

Preconditions

• Python ≥ 3.12 (the SDK uses recent typing features).
• resonate-sdk on PyPI.
• A running Resonate server (resonate dev starts one on localhost:8001). The Rust server v0.9.x runs on a single port — no separate store port.

Install

uv add 'resonate-sdk>=0.7.0'
# or: pip install 'resonate-sdk>=0.7.0'
# or: poetry add 'resonate-sdk>=0.7.0'

Initialize

from __future__ import annotations
import os
from resonate.resonate import Resonate

url = os.environ.get("RESONATE_URL", "http://localhost:8001")

# Connect to a Resonate server
r = Resonate(url=url)

# With a named group (required for rpc routing to a specific worker pool)
r = Resonate(url=url, group="order-workers")

# With a default retry policy
from resonate.retry import Never
r = Resonate(url=url, retry_policy=Never())

One Resonate instance per process. The server is always required for durable execution across restarts and multi-process coordination.

Register a durable function

Durable functions in the Python SDK v0.7.0 are async def coroutines. Register them explicitly after definition:

from typing import TYPE_CHECKING
if TYPE_CHECKING:
    from resonate.context import Context

async def process_order(ctx: Context, order_id: str) -> dict:
    # ctx is the Context; everything inside the function body runs in the durable world
    return {"order_id": order_id, "status": "done"}

r.register(process_order)