Using `uv` for Python package management in KubeRay#

uv is a modern Python package manager written in Rust.

Starting with Ray 2.45, the rayproject/ray:2.45.0 image includes uv as one of its dependencies. This guide provides a simple example of using uv to manage Python dependencies on KubeRay.

To learn more about the uv integration in Ray, refer to:

Example#

Step 1: Create a Kind cluster#

kind create cluster

Step 2: Install KubeRay operator#

Follow the KubeRay Operator Installation to install the latest stable KubeRay operator by Helm repository.

Step 3: Create a RayCluster with `uv` enabled#

ray-cluster.uv.yaml YAML file contains a RayCluster custom resource and a ConfigMap that includes a sample Ray Python script.

The RAY_RUNTIME_ENV_HOOK feature flag enables the uv integration in Ray. Future versions may enable this by default.
```
env:
- name: RAY_RUNTIME_ENV_HOOK
  value: ray._private.runtime_env.uv_runtime_env_hook.hook
```

sample_code.py is a simple Ray Python script that uses the emoji package.

import emoji
import ray

@ray.remote
def f():
    return emoji.emojize('Python is :thumbs_up:')

# Execute 10 copies of f across a cluster.
print(ray.get([f.remote() for _ in range(10)]))

kubectl apply -f https://raw.githubusercontent.com/ray-project/kuberay/master/ray-operator/config/samples/ray-cluster.uv.yaml

Step 4: Execute a Ray Python script with `uv`#

export HEAD_POD=$(kubectl get pods --selector=ray.io/node-type=head -o custom-columns=POD:metadata.name --no-headers)
kubectl exec -it $HEAD_POD -- /bin/bash -c "cd samples && uv run --with emoji /home/ray/samples/sample_code.py"

# [Example output]:
#
# Installed 1 package in 1ms
# 2025-06-01 14:49:15,021 INFO worker.py:1554 -- Using address 127.0.0.1:6379 set in the environment variable RAY_ADDRESS
# 2025-06-01 14:49:15,024 INFO worker.py:1694 -- Connecting to existing Ray cluster at address: 10.244.0.6:6379...
# 2025-06-01 14:49:15,035 INFO worker.py:1879 -- Connected to Ray cluster. View the dashboard at 10.244.0.6:8265
# 2025-06-01 14:49:15,040 INFO packaging.py:576 -- Creating a file package for local module '/home/ray/samples'.
# 2025-06-01 14:49:15,041 INFO packaging.py:368 -- Pushing file package 'gcs://_ray_pkg_d4da2ce33cf6d176.zip' (0.00MiB) to Ray cluster...
# 2025-06-01 14:49:15,042 INFO packaging.py:381 -- Successfully pushed file package 'gcs://_ray_pkg_d4da2ce33cf6d176.zip'.
# ['Python is 👍', 'Python is 👍', 'Python is 👍', 'Python is 👍', 'Python is 👍', 'Python is 👍', 'Python is 👍', 'Python is 👍', 'Python is 👍', 'Python is 👍']

NOTE: Use /bin/bash -c to execute the command while changing the current directory to /home/ray/samples. By default, working_dir is set to the current directory. This prevents uploading all files under /home/ray, which can take a long time when executing uv run. Alternatively, you can use ray job submit --runtime-env-json ... to specify the working_dir manually.

Using uv for Python package management in KubeRay#