Deploy to Kubernetes

The easiest way to deploy YuniKorn is to leverage our helm charts, you can find the guide here. This document describes the manual process to deploy YuniKorn scheduler and it is majorly for developers.

Build docker image

Under project root of the yunikorn-k8shim, run the command to build an image using the map for the configuration:

make image

This command will build an image. The image will be tagged with a default version and image tag.

Note the default build uses a hardcoded user and tag. You must update the IMAGE_TAG variable in the Makefile to push to an appropriate repository.

Note the latest yunikorn images in docker hub are not updated anymore due to ASF policy. Hence, you should build both scheduler image and web image locally before deploying them.

Setup RBAC

The first step is to create the RBAC role for the scheduler, see yunikorn-rbac.yaml

kubectl create -f scheduler/yunikorn-rbac.yaml

The role is a requirement on the current versions of kubernetes.

Create the ConfigMap

This must be done before deploying the scheduler. It requires a correctly setup kubernetes environment. This kubernetes environment can be either local or remote.

• download configuration file if not available on the node to add to kubernetes:

curl -o queues.yaml https://raw.githubusercontent.com/apache/incubator-yunikorn-k8shim/master/conf/queues.yaml

• create ConfigMap in kubernetes:

kubectl create configmap yunikorn-configs --from-file=queues.yaml

• check if the ConfigMap was created correctly:

kubectl describe configmaps yunikorn-configs

Note if name of the ConfigMap is changed the volume in the scheduler yaml file must be updated to reference the new name otherwise the changes to the configuration will not be picked up.

Attach ConfigMap to the Scheduler Pod

The ConfigMap is attached to the scheduler as a special volume. First step is to specify where to mount it in the pod:

  volumeMounts:
    - name: config-volume
      mountPath: /etc/yunikorn/

Second step is to link the mount point back to the configuration map created in kubernetes:

  volumes:
    - name: config-volume
      configMap:
        name: yunikorn-configs

Both steps are part of the scheduler yaml file, an example can be seen at scheduler.yaml for reference.

Deploy the Scheduler

The scheduler can be deployed with following command.

kubectl create -f deployments/scheduler/scheduler.yaml

The deployment will run 2 containers from your pre-built docker images in 1 pod,

• yunikorn-scheduler-core (yunikorn scheduler core and shim for K8s)
• yunikorn-scheduler-web (web UI)

The pod is deployed as a customized scheduler, it will take the responsibility to schedule pods which explicitly specifies schedulerName: yunikorn in pod's spec. In addition to the schedulerName, you will also have to add a label applicationId to the pod.

  metadata:
    name: pod_example
    labels:
      applicationId: appID
  spec:
    schedulerName: yunikorn

Note: Admission controller abstracts the addition of schedulerName and applicationId from the user and hence, routes all traffic to YuniKorn. If you use helm chart to deploy, it will install admission controller along with the scheduler.

Access to the web UI

When the scheduler is deployed, the web UI is also deployed in a container. Port forwarding for the web interface on the standard ports can be turned on via:

POD=`kubectl get pod -l app=yunikorn -o jsonpath="{.items[0].metadata.name}"` && \
kubectl port-forward ${POD} 9889 9080

9889 is the default port for Web UI, 9080 is the default port of scheduler's Restful service where web UI retrieves info from. Once this is done, web UI will be available at: http://localhost:9889.

Configuration Hot Refresh

YuniKorn supports to load configuration changes automatically from attached configmap. Simply update the content in the configmap, that can be done either via Kubernetes dashboard UI or commandline. Note, changes made to the configmap might have some delay to be picked up by the scheduler.