constellation/coordinator/kubernetes/k8sapi/util.go

package k8sapi

import (
	"errors"
	"fmt"
	"os"
	"os/exec"
	"strings"

	"github.com/edgelesssys/constellation/coordinator/kubernetes/k8sapi/resources"
	kubeadm "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta3"
)

// kubeConfig is the path to the kubernetes admin config (used for authentication).
const kubeConfig = "/etc/kubernetes/admin.conf"

// Client provides the functionality of `kubectl apply`.
type Client interface {
	Apply(resources resources.Marshaler, forceConflicts bool) error
	SetKubeconfig(kubeconfig []byte)
	// TODO: add tolerations
}

type ClusterUtil interface {
	InitCluster(initConfig []byte) (*kubeadm.BootstrapTokenDiscovery, error)
	JoinCluster(joinConfig []byte) error
	SetupPodNetwork(kubectl Client, podNetworkConfiguration resources.Marshaler) error
	SetupAutoscaling(kubectl Client, clusterAutoscalerConfiguration resources.Marshaler) error
	SetupCloudControllerManager(kubectl Client, cloudControllerManagerConfiguration resources.Marshaler) error
	RestartKubelet() error
}

type KubernetesUtil struct{}

func (k *KubernetesUtil) InitCluster(initConfig []byte) (*kubeadm.BootstrapTokenDiscovery, error) {
	initConfigFile, err := os.CreateTemp("", "kubeadm-init.*.yaml")
	if err != nil {
		return nil, fmt.Errorf("failed to create init config file %v: %w", initConfigFile.Name(), err)
	}
	defer os.Remove(initConfigFile.Name())

	if _, err := initConfigFile.Write(initConfig); err != nil {
		return nil, fmt.Errorf("writing kubeadm init yaml config %v failed: %w", initConfigFile.Name(), err)
	}

	cmd := exec.Command("kubeadm", "init", "--config", initConfigFile.Name())
	stdout, err := cmd.Output()
	if err != nil {
		var exitErr *exec.ExitError
		if errors.As(err, &exitErr) {
			return nil, fmt.Errorf("kubeadm init failed (code %v) with: %s", exitErr.ExitCode(), exitErr.Stderr)
		}
		return nil, fmt.Errorf("kubeadm init failed: %w", err)
	}

	stdoutStr := string(stdout)
	indexKubeadmJoin := strings.Index(stdoutStr, "kubeadm join")
	if indexKubeadmJoin < 0 {
		return nil, errors.New("kubeadm init did not return join command")
	}

	joinCommand := strings.ReplaceAll(stdoutStr[indexKubeadmJoin:], "\\\n", " ")
	// `kubeadm init` returns the two join commands, each broken up into two lines with backslash + newline in between.
	// The following functions assume that stdoutStr[indexKubeadmJoin:] look like the following string.

	// -----------------------------------------------------------------------------------------------
	// --- When modifying the kubeadm.InitConfiguration make sure that this assumption still holds ---
	// -----------------------------------------------------------------------------------------------

	// "kubeadm join 127.0.0.1:16443 --token vlhjr4.9l6lhek0b9v65m67 \
	//	--discovery-token-ca-cert-hash sha256:2b5343a162e31b70602e3cab3d87189dc10431e869633c4db63c3bfcd038dee6 \
	//	--control-plane
	//
	// Then you can join any number of worker nodes by running the following on each as root:
	//
	// kubeadm join 127.0.0.1:16443 --token vlhjr4.9l6lhek0b9v65m67 \
	//  --discovery-token-ca-cert-hash sha256:2b5343a162e31b70602e3cab3d87189dc10431e869633c4db63c3bfcd038dee6"

	// Splits the string into a slice, where earch slice-element contains one line from the previous string
	splittedJoinCommand := strings.SplitN(joinCommand, "\n", 2)

	return ParseJoinCommand(splittedJoinCommand[0])
}

// SetupPodNetwork sets up the flannel pod network.
func (k *KubernetesUtil) SetupPodNetwork(kubectl Client, podNetworkConfiguration resources.Marshaler) error {
	if err := kubectl.Apply(podNetworkConfiguration, true); err != nil {
		return err
	}

	// allow coredns to run on uninitialized nodes (required by cloud-controller-manager)
	err := exec.Command("kubectl", "--kubeconfig", kubeConfig, "-n", "kube-system", "patch", "deployment", "coredns", "--type", "json", "-p", "[{\"op\":\"add\",\"path\":\"/spec/template/spec/tolerations/-\",\"value\":{\"key\":\"node.cloudprovider.kubernetes.io/uninitialized\",\"value\":\"true\",\"effect\":\"NoSchedule\"}}]").Run()
	if err != nil {
		return err
	}
	return exec.Command("kubectl", "--kubeconfig", kubeConfig, "-n", "kube-system", "patch", "deployment", "coredns", "--type", "json", "-p", "[{\"op\":\"add\",\"path\":\"/spec/template/spec/tolerations/-\",\"value\":{\"key\":\"node.kubernetes.io/network-unavailable\",\"value\":\"\",\"effect\":\"NoSchedule\"}}]").Run()
}

func (k *KubernetesUtil) SetupAutoscaling(kubectl Client, clusterAutoscalerConfiguration resources.Marshaler) error {
	return kubectl.Apply(clusterAutoscalerConfiguration, true)
}

func (k *KubernetesUtil) SetupCloudControllerManager(kubectl Client, cloudControllerManagerConfiguration resources.Marshaler) error {
	return kubectl.Apply(cloudControllerManagerConfiguration, true)
}

// JoinCluster joins existing kubernetes cluster using kubeadm join.
func (k *KubernetesUtil) JoinCluster(joinConfig []byte) error {
	joinConfigFile, err := os.CreateTemp("", "kubeadm-join.*.yaml")
	if err != nil {
		return fmt.Errorf("failed to create join config file %v: %w", joinConfigFile.Name(), err)
	}
	defer os.Remove(joinConfigFile.Name())

	if _, err := joinConfigFile.Write(joinConfig); err != nil {
		return fmt.Errorf("writing kubeadm init yaml config %v failed: %w", joinConfigFile.Name(), err)
	}

	// run `kubeadm join` to join a worker node to an existing kubernetes cluster
	cmd := exec.Command("kubeadm", "join", "--config", joinConfigFile.Name())
	if _, err := cmd.Output(); err != nil {
		var exitErr *exec.ExitError
		if errors.As(err, &exitErr) {
			return fmt.Errorf("kubeadm join failed (code %v) with: %s", exitErr.ExitCode(), exitErr.Stderr)
		}
		return fmt.Errorf("kubeadm join failed: %w", err)
	}
	return nil
}

// RestartKubelet restarts a kubelet.
func (k *KubernetesUtil) RestartKubelet() error {
	return RestartSystemdUnit("kubelet.service")
}