cordon.go

/*
Copyright 2019 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package drain

import (
	"fmt"

	corev1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/schema"

	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/json"
	"k8s.io/apimachinery/pkg/util/strategicpatch"
	"k8s.io/client-go/kubernetes"
)

// CordonHelper wraps functionality to cordon/uncordon nodes
type CordonHelper struct {
	node    *corev1.Node
	desired bool
}

// NewCordonHelper returns a new CordonHelper
func NewCordonHelper(node *corev1.Node) *CordonHelper {
	return &CordonHelper{
		node: node,
	}
}

// NewCordonHelperFromRuntimeObject returns a new CordonHelper, or an error if given object is not a
// node or cannot be encoded as JSON
func NewCordonHelperFromRuntimeObject(nodeObject runtime.Object, scheme *runtime.Scheme, gvk schema.GroupVersionKind) (*CordonHelper, error) {
	nodeObject, err := scheme.ConvertToVersion(nodeObject, gvk.GroupVersion())
	if err != nil {
		return nil, err
	}

	node, ok := nodeObject.(*corev1.Node)
	if !ok {
		return nil, fmt.Errorf("unexpected type %T", nodeObject)
	}

	return NewCordonHelper(node), nil
}

// UpdateIfRequired returns true if c.node.Spec.Unschedulable isn't already set,
// or false when no change is needed
func (c *CordonHelper) UpdateIfRequired(desired bool) bool {
	c.desired = desired
	if c.node.Spec.Unschedulable == c.desired {
		return false
	}
	return true
}

// PatchOrReplace uses given clientset to update the node status, either by patching or
// updating the given node object; it may return error if the object cannot be encoded as
// JSON, or if either patch or update calls fail; it will also return a second error
// whenever creating a patch has failed
func (c *CordonHelper) PatchOrReplace(clientset kubernetes.Interface) (error, error) {
	client := clientset.CoreV1().Nodes()

	oldData, err := json.Marshal(c.node)
	if err != nil {
		return err, nil
	}

	c.node.Spec.Unschedulable = c.desired

	newData, err := json.Marshal(c.node)
	if err != nil {
		return err, nil
	}

	patchBytes, patchErr := strategicpatch.CreateTwoWayMergePatch(oldData, newData, c.node)
	if patchErr == nil {
		_, err = client.Patch(c.node.Name, types.StrategicMergePatchType, patchBytes)
	} else {
		_, err = client.Update(c.node)
	}
	return err, patchErr
}