dagster-ray

---

Ray integration library for Dagster.

dagster-ray allows running Ray computations in Dagster pipelines. It provides various Dagster abstractions, the most important being Resource, and helper @ops and @schedules, for multiple backends.

The following backends are implemented:

• local
• KubeRay (kubernetes)

dagster-ray is tested across multiple version combinations of components such as ray, dagster, KubeRay Operator, and Python.

dagster-ray integrates with Dagster+ out of the box.

Documentation can be found below.

Note

This project is in early development. Contributions are very welcome! See the Development section below.

Installation

pip install dagster-ray

To install with extra dependencies for a particular backend (like kuberay), run:

pip install 'dagster-ray[kuberay]'

Backends

dagster-ray provides a RayResource class, which does not implement any specific backend. It defines the common interface for all Ray resources. It can be used for type annotations in your @op and @asset definitions.

Examples:

from dagster import asset
from dagster_ray import RayResource
import ray


@asset
def my_asset(
    ray_cluster: RayResource,  # RayResource is only used as a type annotation
):
    return ray.get(ray.put(42))

The other resources below are the actual backends that implement the RayResource interface.

Local

These resources can be used for development and testing purposes. They provide the same interface as the other *Ray resources, but don't require any external infrastructure.

The public objects can be imported from dagster_ray.local module.

Resources

LocalRay

A dummy resource which is useful for testing and development. It doesn't do anything, but provides the same interface as the other *Ray resources.

Examples:

Using the LocalRay resource

from dagster import asset, Definitions
from dagster_ray import RayResource
from dagster_ray.local import LocalRay
import ray


@asset
def my_asset(
    ray_cluster: RayResource,  # RayResource is only used as a type annotation
):  # this type annotation only defines the interface
    return ray.get(ray.put(42))


definitions = Definitions(resources={"ray_cluster": LocalRay()}, assets=[my_asset])

Conditionally using the LocalRay resource in development and KubeRayCluster in production:

from dagster import asset, Definitions
from dagster_ray import RayResource
from dagster_ray.local import LocalRay
from dagster_ray.kuberay import KubeRayCluster
import ray


@asset
def my_asset(
    ray_cluster: RayResource,  # RayResource is only used as a type annotation
):  # this type annotation only defines the interface
    return ray.get(ray.put(42))


IN_K8s = ...


definitions = Definitions(
    resources={"ray_cluster": KubeRayCluster() if IN_K8s else LocalRay()},
    assets=[my_asset],
)

KubeRay

This backend requires a Kubernetes cluster with the KubeRay Operator installed.

Integrates with Dagster+ by injecting environment variables such as DAGSTER_CLOUD_DEPLOYMENT_NAME and tags such as dagster/user into default configuration values and RayCluster labels.

The public objects can be imported from dagster_ray.kuberay module.

Resources

KubeRayCluster

KubeRayCluster can be used for running Ray computations on Kubernetes.

When added as resource dependency to an @op/@asset, the KubeRayCluster:

• Starts a dedicated RayCluster for it
• Connects to the cluster in client mode with ray.init() (unless skip_init is set to True)
• Tears down the cluster after the step is executed (unless skip_cleanup is set to True)

RayCluster comes with minimal default configuration, matching KubeRay defaults.

Examples:

Basic usage (will create a single-node, non-scaling RayCluster):

from dagster import asset, Definitions
from dagster_ray import RayResource
from dagster_ray.kuberay import KubeRayCluster
import ray


@asset
def my_asset(
    ray_cluster: RayResource,  # RayResource is only used as a type annotation
):  # this type annotation only defines the interface
    return ray.get(ray.put(42))


definitions = Definitions(
    resources={"ray_cluster": KubeRayCluster()}, assets=[my_asset]
)

Larger cluster with auto-scaling enabled:

from dagster_ray.kuberay import KubeRayCluster, RayClusterConfig

ray_cluster = KubeRayCluster(
    ray_cluster=RayClusterConfig(
        enable_in_tree_autoscaling=True,
        worker_group_specs=[
            {
                "groupName": "workers",
                "replicas": 2,
                "minReplicas": 1,
                "maxReplicas": 10,
                # ...
            }
        ],
    )
)

KubeRayAPI

This resource can be used to interact with the Kubernetes API Server.

Examples:

Listing currently running RayClusters:

from dagster import op, Definitions
from dagster_ray.kuberay import KubeRayAPI


@op
def list_ray_clusters(
    kube_ray_api: KubeRayAPI,
):
    return kube_ray_api.kuberay.list_ray_clusters(k8s_namespace="kuberay")

Jobs

delete_kuberay_clusters

This job can be used to delete RayClusters from a given list of names.

cleanup_old_ray_clusters

This job can be used to delete old RayClusters which no longer correspond to any active Dagster Runs. They may be left behind if the automatic cluster cleanup was disabled or failed.

Schedules

Cleanup schedules can be trivially created using the cleanup_old_ray_clusters or delete_kuberay_clusters jobs.

cleanup_old_ray_clusters

dagster-ray provides an example daily cleanup schedule.

Executor

WIP

Development

poetry install --all-extras
poetry shell
pre-commit install

Testing

KubeRay

Required tools:

• docker
• kubectl
• helm
• minikube

Running pytest will automatically:

• build an image with the local dagster-ray code
• start a minikube Kubernetes cluster
• load the built dagster-ray and loaded kuberay-operator images into the cluster
• install the KubeRay Operator in the cluster with helm
• run the tests

Thus, no manual setup is required, just the presence of the tools listed above. This makes testing a breeze!

Note

Specifying a comma-separated list of KubeRay Operator versions in the KUBE_RAY_OPERATOR_VERSIONS environment variable will spawn a new test for each version.

Note

it may take a while to download minikube and kuberay-operator images and build the local dagster-ray image during the first tests invocation