k8s-scheduler-extender-example

This is an example of Kubernetes Scheduler Extender

How to

1. buid a docker image

$ IMAGE=YOUR_ORG/YOUR_IMAGE:YOUR_TAG

$ docker build . -t "${IMAGE}"
$ docker push "${IMAGE}"

2. deploy my-scheduler in kube-system namespace

please see ConfigMap in extender.yaml for scheduler policy json which includes scheduler extender config.

# bring up the kube-scheduler along with the extender image you've just built
$ sed 's/a\/b:c/'$(echo "${IMAGE}" | sed 's/\//\\\//')'/' extender.yaml | kubectl apply -f -

For ease of observation, start streaming logs from the extender:

$ kubectl -n kube-system logs deploy/my-scheduler -c my-scheduler-extender-ctr -f
[  warn ] 2018/11/07 08:41:40 main.go:84: LOG_LEVEL="" is empty or invalid, fallling back to "INFO".
[  info ] 2018/11/07 08:41:40 main.go:98: Log level was set to INFO
[  info ] 2018/11/07 08:41:40 main.go:116: server starting on the port :80

Open up an another termianl and proceed.

3. schedule test pod

you will see test-pod will be scheduled by my-scheduler.

$ kubectl create -f test-pod.yaml

$ kubectl describe pod test-pod
Name:         test-pod
...
Events:
  Type    Reason                 Age   From               Message
  ----    ------                 ----  ----               -------
  Normal  Scheduled              25s   my-scheduler       Successfully assigned test-pod to minikube
  Normal  SuccessfulMountVolume  25s   kubelet, minikube  MountVolume.SetUp succeeded for volume "default-token-wrk5s"
  Normal  Pulling                24s   kubelet, minikube  pulling image "nginx"
  Normal  Pulled                 8s    kubelet, minikube  Successfully pulled image "nginx"
  Normal  Created                8s    kubelet, minikube  Created container
  Normal  Started                8s    kubelet, minikube  Started container