Restate Python SDK

Restate is a system for easily building resilient applications using distributed durable async/await. This repository contains the Restate SDK for writing services in Python.

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Using the SDK

Prerequisites:

• Python >= v3.11

To use this SDK, add the dependency to your project:

pip install restate_sdk

Serving using an ASGI server

Given an app.py:

import restate

greeter = restate.Service("greeter")

@greeter.handler()
async def greet(ctx: restate.Context, name: str) -> str:
    return f"Hello {name}!"

app = restate.app(services=[greeter])

restate.app takes services, virtual objects and workflows, and anything else that is a restate.Servable: session objects, and agents, which bring along the signals object their tools wait on. Each is served once, however many things bring it along.

Serve it with restate.serve, which needs the serve extra (pip install "restate-sdk[serve]"). It listens on $PORT, or 9080, with the HTTP/2 that Restate connects with, and stops on SIGINT or SIGTERM:

if __name__ == "__main__":
    import asyncio

    asyncio.run(restate.serve(app))

Or from the command line, with no __main__ block: python -m restate serve app:app (--port to choose the port).

restate.app(...) returns an ASGI application, so any ASGI server can serve it instead, for example Hypercorn:

pip install hypercorn
python -m hypercorn app:app --bind "0.0.0.0:9080"

Once served, register the deployment with restate deployments register http://localhost:9080.

Connecting to Restate Cloud

An application can connect outbound to Restate Cloud instead of exposing a port. Copy a connect key from the Cloud UI -> Development → Configure SDK, pick a name for the deployment, and run:

RESTATE_CONNECT_KEY=rstcloudv1_... python -m restate connect app:app --name greeter-v1

Then register the deployment as connect://greeter-v1.

The same from code:

if __name__ == "__main__":
    import asyncio
    
    asyncio.run(restate.connect(app, name="greeter-v1"))

Or using the context manager, for finer control:

async with restate.with_connection(app, name="greeter-v1") as connection:
    print(connection.info.deployment_url)
    await connection.wait_closed()

Clients

restate.create_client() without a URL connects to Restate Cloud using the ingress key in RESTATE_INGRESS_KEY, copied from the Cloud UI -> Development → Configure SDK.

Versions

The compatibility with Restate is described in the following table. sdk-python versions < 0.10 are deprecated and no longer supported.

Restate Server\sdk-python	0.10 - 0.18	1.0
< 1.3	❌	❌
1.3 - 1.4	✅ (1)	✅ (1)(2)
1.5 - 1.6	✅	✅ (2)
1.7	✅	✅
1.8	✅	✅ (3)

⁽¹⁾ Note The new Service/Object/Workflow constructor field and the decorator field invocation_retry_policy works only from Restate 1.4 onward. Check the in-code documentation for more details.

⁽²⁾ Note Scopes and limit keys work only from Restate 1.7 onward. Check the in-code documentation for more details.

⁽³⁾ Note The list form of state_preload (eager state keys whitelist) works only from Restate 1.8 onward. Check the in-code documentation for more details.

Contributing

We’re excited if you join the Restate community and start contributing! Whether it is feature requests, bug reports, ideas & feedback or PRs, we appreciate any and all contributions. We know that your time is precious and, therefore, deeply value any effort to contribute!

Local development

• Python 3
• PyEnv or VirtualEnv
• just
• Rust toolchain

Set up your virtual environment using the tool of your choice, e.g. VirtualEnv:

python3 -m venv .venv
source .venv/bin/activate

Install the build tools:

pip install -r requirements.txt

Now build the Rust module and include opt-in additional dev dependencies:

maturin dev -E test,lint

You usually need to build the Rust module only once, but you might need to rebuild it on pulls.

For linting and testing:

just verify

Releasing the package

Pull latest main:

git checkout main && git pull

Update module version in Cargo.toml and run a local build to update the Cargo.lock too, commit it. Then push tag, e.g.:

git tag -m "Release v0.1.0" v0.1.0
git push origin v0.1.0