[Feature] [Docs] Improve docs around KubeRay API server installation

[DmitriGekhtman]

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• [X] I had searched in the issues and found no similar feature requirement.

Description

Docs around KubeRay API server installation should be improved.

• Document installing the KubeRay API server using Helm

There is a Helm chart available for deployment of the KubeRay API server. It is not documented yet. That should be fixed.

• Clearly distinguish the following actions in the docs

Installing the KubeRay Operator. Installing the KubeRay API Server. Installing both the KubeRay API Server and the KubeRay Operator.

Use case

No response

Related issues

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Are you willing to submit a PR?

• [ ] Yes I am willing to submit a PR!

[dhaval0108]

Couple of suggestions for the documentation from my experience

1. The image used in the current docs for cluster creation i.e. ray.io/ray:1.9.2 seems to be outdated and led to ImagePullBackOff. Using rayproject/ray:2.0.0 resolved the issue for me.
2. rayStartParams for both head and worker nodes seems to be a required parameter. Upon passing an empty dictionary I kept getting [spec.workerGroupSpecs.rayStartParams: Required value, spec.headGroupSpec.rayStartParams: Required value]. Adding any dummy key-value pair did not work either. Eventually, adding "rayStartParams": {"num-cpus": "1"} resolved the issue. Thus, documenting the acceptable parameters would be really helpful.
3. Having documentation for how to submit a job to a specific cluster with an example would be really helpful too.

Thank you for documenting the apiserver in the first place, it has really helped me set up the apiserver and get it running!