Simple client to set kubernetes node conditions.

main.go

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"time"

	_ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
	"gopkg.in/alecthomas/kingpin.v2"
	core "k8s.io/api/core/v1"
	meta "k8s.io/apimachinery/pkg/apis/meta/v1"
	client "k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/client-go/tools/clientcmd/api"
)

var (
	app             = kingpin.New(filepath.Base(os.Args[0]), "Sets an arbitary node-condition on a given node.").DefaultEnvars()
	kubecfg         = app.Flag("kubeconfig", "Kubeconfig location.").String()
	nodeName        = app.Flag("node-name", "Name of the node to affect.").Required().String()
	conditionName   = app.Flag("condition-name", "Name of the condition to modify.").String()
	conditionStatus = app.Flag("condition-status", "Condition status, should be one of True/False/Unknown.").String()
	conditionUnset  = app.Flag("unset", "Unset the condition instead of modifying it.").Short('u').Bool()
)

func main() {
	kingpin.MustParse(app.Parse(os.Args[1:]))

	c, err := BuildConfigFromFlags("", *kubecfg)
	kingpin.FatalIfError(err, "cannot create Kubernetes client configuration")

	cs, err := client.NewForConfig(c)
	kingpin.FatalIfError(err, "cannot create Kubernetes client")

	node, err := cs.CoreV1().Nodes().Get(context.TODO(), *nodeName, meta.GetOptions{})
	kingpin.FatalIfError(err, "cannot get node by the name provided")

	statusToSet := core.ConditionUnknown
	switch *conditionStatus {
	case "True":
		statusToSet = core.ConditionTrue
	case "False":
		statusToSet = core.ConditionFalse
	case "Unknown":
		statusToSet = core.ConditionUnknown
	default:
		kingpin.Fatalf("Invalid condition value, use True, False or Unknown.")
	}

	node.Status.Conditions = []core.NodeCondition{
		core.NodeCondition{
			Type:               core.NodeConditionType(*conditionName),
			Status:             statusToSet,
			LastHeartbeatTime:  meta.Time{time.Now()},
			LastTransitionTime: meta.Time{time.Now()},
			Reason:             "NodeConditioner",
			Message:            "Condition set via CLI.",
		},
	}

	node, err = cs.CoreV1().Nodes().UpdateStatus(context.TODO(), node, meta.UpdateOptions{})
	if err != nil {
		kingpin.FatalIfError(err, "Could not update node status.")
	}

	bytes, err := json.Marshal(node)
	if err != nil {
		kingpin.FatalIfError(err, "Could not marshal returned node.")
	}

	fmt.Println("Node condition modified successfully:")
	fmt.Println(string(bytes))
}

// BuildConfigFromFlags is clientcmd.BuildConfigFromFlags with no annoying
// dependencies on glog.
// https://godoc.org/k8s.io/client-go/tools/clientcmd#BuildConfigFromFlags
func BuildConfigFromFlags(apiserver, kubecfg string) (*rest.Config, error) {
	if kubecfg != "" || apiserver != "" {
		return clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
			&clientcmd.ClientConfigLoadingRules{ExplicitPath: kubecfg},
			&clientcmd.ConfigOverrides{ClusterInfo: api.Cluster{Server: apiserver}}).ClientConfig()
	}
	return rest.InClusterConfig()
}