Inject cluster name as an environment variable into head and worker pods

[Yicheng-Lu-llll]

Why are these changes needed?

See #928.

Now user can get env var RAY_CLUSTER_NAME in head and worker pods.

Related issue number

Closes #928

Checks

rootPath={Your kuberay repo path}
# ray-cluster.complete.yaml will create one head pod and one worker pod.
kubectl apply -f $rootPath/ray-operator/config/samples/ray-cluster.complete.yaml
kubectl exec -it $(kubectl get pods -o=name | grep head) -- env | grep RAY_CLUSTER_NAME
kubectl exec -it $(kubectl get pods -o=name | grep worker) -- env | grep RAY_CLUSTER_NAME
# Now change the pod replicas to 2, kuberay operator will create a new worker pod, check if the newly created pod also have env vars.
kubectl apply -f $rootPath/ray-operator/config/samples/ray-cluster.complete.yaml
kubectl exec -it raycluster-complete-worker-small-group-fw6kk -- env | grep RAY_CLUSTER_NAME


# will always see:
# RAY_CLUSTER_NAME=raycluster-complete

[kevin85421]

Thank you for your contribution! Could you

(1) Think about the comparisons between injecting the env variable by KubeRay operator or setting by YAML files.

(2) Add some tests.

(3) Test autoscaler.

[kevin85421]

Check whether BuildPod will always be called after DefaultWorkerPodTemplate and DefaultHeadPodTemplate.

[kevin85421]

This looks like a better solution?

https://github.com/ray-project/kuberay/blob/master/ray-operator/controllers/ray/common/pod.go#L386

[Yicheng-Lu-llll]

This looks like a better solution?

https://github.com/ray-project/kuberay/blob/master/ray-operator/controllers/ray/common/pod.go#L386

Updated. Thank you for pointing that out!

[kevin85421]

Can you add a document for environment_variables? Thanks!

[kevin85421]

Should we also update this line?

kuberay/ray-operator/controllers/ray/common/pod_test.go

Line 194 in 1a8895e

Name: "RAY_CLUSTER_NAME",

and this one

kuberay/ray-operator/controllers/ray/common/pod_test.go

Line 197 in 1a8895e

FieldPath: "metadata.labels['ray.io/cluster']",

[kevin85421]

LGTM. I also tested this PR manually.