mini-kube-scheduler

README

mini-kube-scheduler: Scheduler for learning Kubernetes Scheduler

This scheduler is not for production

日本語版はこちら(Japanese ver)

Hello world.

This is mini-kube-scheduler -- the scheduler for learning Kubernetes Scheduler.

And this repository also has scenario system. You can write scenario like this and check the scheduler's behaviours.

func scenario(client clientset.Interface) error {
	ctx := context.Background()

	// create node0 ~ node9, but all nodes are unschedulable
	for i := 0; i < 9; i++ {
		suffix := strconv.Itoa(i)
		_, err := client.CoreV1().Nodes().Create(ctx, &v1.Node{
			ObjectMeta: metav1.ObjectMeta{
				Name: "node" + suffix,
			},
			Spec: v1.NodeSpec{
				Unschedulable: true,
			},
		}, metav1.CreateOptions{})
		if err != nil {
			return fmt.Errorf("create node: %w", err)
		}
	}

	klog.Info("scenario: all nodes created")

	_, err := client.CoreV1().Pods("default").Create(ctx, &v1.Pod{
		ObjectMeta: metav1.ObjectMeta{Name: "pod1"},
		Spec: v1.PodSpec{
			Containers: []v1.Container{
				{
					Name:  "container1",
					Image: "k8s.gcr.io/pause:3.5",
				},
			},
		},
	}, metav1.CreateOptions{})
	if err != nil {
		return fmt.Errorf("create pod: %w", err)
	}

	klog.Info("scenario: pod1 created")

	// wait to schedule
	time.Sleep(3 * time.Second)

	pod1, err := client.CoreV1().Pods("default").Get(ctx, "pod1", metav1.GetOptions{})
	if err != nil {
		return fmt.Errorf("get pod: %w", err)
	}

    klog.Info("scenario: pod1 is bound to " + pod1.Spec.NodeName)
	
    return nil
}

The evolution of Scheduler

The scheduler evolves step by step, branch by branch. You can use them to learn the scheduler step by step.

TODO: I'm planning to add docs to describe what is new feature for each branchs.

1. initial scheduler

This scheduler selects node for pod randomly.

1. filter plugins

This scheduler selects node for pod with only filter plugin. Only unschedulable node plugin is enabled as filter plugin.

1. score plugins

This scheduler selects node for pod with filter and score plugin. Only nodenumber plugin(implemented as custom plugin) is enabled as score plugin.

1. prescore plugins

This scheduler supports pre-score plugins. The nodenumber plugin is improved so that it is also used as prescore plugins.

1. permit plugins

This scheduler supports permit plugins. The nodenumber plugin is improved so that it is also used as permit plugins. And binding cycle is now goroutined(work in parallel).

1. scheduling queue

This branch implements Scheduling Queue. It also supports putting the Pod back into the Queue as unschedulable when the schedule fails.

1. eventhandler

This branch has support for updating Queues using EventHandler. It supports re-scheduling of pods that fail to schedule.

custom main logic of this scheduler

Most of the codes for this scheduler is placed under /minisched. You can change this scheduler to what you want.

And this scheduler is started on here

If you want to change how to start the scheduler, you can change here.

custom scenario

You can write scenario here and check this scheduler's behaviour.

How to start this scheduler and scenario

To run this scheduler and start scenario, you have to install Go and etcd. You can install etcd with kubernetes/kubernetes/hack/install-etcd.sh.

And, make start starts your scenario.

Note

This mini-kube-scheduler starts scheduler, etcd, api-server and pv-controller.

The whole mechanism is based on kubernetes-sigs/kube-scheduler-simulator