kubernetes/cmd/kubeadm/app/util/runtime/runtime.go

/*
Copyright 2018 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 runtime

import (
	"strings"

	"github.com/pkg/errors"

	errorsutil "k8s.io/apimachinery/pkg/util/errors"
	utilsexec "k8s.io/utils/exec"

	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
)

// defaultKnownCRISockets holds the set of known CRI endpoints
var defaultKnownCRISockets = []string{
	constants.CRISocketContainerd,
	constants.CRISocketCRIO,
	constants.CRISocketDocker,
}

// ContainerRuntime is an interface for working with container runtimes
type ContainerRuntime interface {
	Socket() string
	IsRunning() error
	ListKubeContainers() ([]string, error)
	RemoveContainers(containers []string) error
	PullImage(image string) error
	ImageExists(image string) (bool, error)
}

// CRIRuntime is a struct that interfaces with the CRI
type CRIRuntime struct {
	exec       utilsexec.Interface
	criSocket  string
	crictlPath string
}

// NewContainerRuntime sets up and returns a ContainerRuntime struct
func NewContainerRuntime(execer utilsexec.Interface, criSocket string) (ContainerRuntime, error) {
	const toolName = "crictl"
	crictlPath, err := execer.LookPath(toolName)
	if err != nil {
		return nil, errors.Wrapf(err, "%s is required by the container runtime", toolName)
	}
	return &CRIRuntime{execer, criSocket, crictlPath}, nil
}

// Socket returns the CRI socket endpoint
func (runtime *CRIRuntime) Socket() string {
	return runtime.criSocket
}

// crictl creates a crictl command for the provided args.
func (runtime *CRIRuntime) crictl(args ...string) utilsexec.Cmd {
	return runtime.exec.Command(runtime.crictlPath, append([]string{"-r", runtime.Socket()}, args...)...)
}

// IsRunning checks if runtime is running
func (runtime *CRIRuntime) IsRunning() error {
	if out, err := runtime.crictl("info").CombinedOutput(); err != nil {
		return errors.Wrapf(err, "container runtime is not running: output: %s, error", string(out))
	}
	return nil
}

// ListKubeContainers lists running k8s CRI pods
func (runtime *CRIRuntime) ListKubeContainers() ([]string, error) {
	out, err := runtime.crictl("pods", "-q").CombinedOutput()
	if err != nil {
		return nil, errors.Wrapf(err, "output: %s, error", string(out))
	}
	pods := []string{}
	pods = append(pods, strings.Fields(string(out))...)
	return pods, nil
}

// RemoveContainers removes running k8s pods
func (runtime *CRIRuntime) RemoveContainers(containers []string) error {
	errs := []error{}
	for _, container := range containers {
		out, err := runtime.crictl("stopp", container).CombinedOutput()
		if err != nil {
			// don't stop on errors, try to remove as many containers as possible
			errs = append(errs, errors.Wrapf(err, "failed to stop running pod %s: output: %s, error", container, string(out)))
		} else {
			out, err = runtime.crictl("rmp", container).CombinedOutput()
			if err != nil {
				errs = append(errs, errors.Wrapf(err, "failed to remove running container %s: output: %s, error", container, string(out)))
			}
		}
	}
	return errorsutil.NewAggregate(errs)
}

// PullImage pulls the image
func (runtime *CRIRuntime) PullImage(image string) error {
	var err error
	var out []byte
	for i := 0; i < constants.PullImageRetry; i++ {
		out, err = runtime.crictl("pull", image).CombinedOutput()
		if err == nil {
			return nil
		}
	}
	return errors.Wrapf(err, "output: %s, error", out)
}

// ImageExists checks to see if the image exists on the system
func (runtime *CRIRuntime) ImageExists(image string) (bool, error) {
	err := runtime.crictl("inspecti", image).Run()
	return err == nil, nil
}

// detectCRISocketImpl is separated out only for test purposes, DON'T call it directly, use DetectCRISocket instead
func detectCRISocketImpl(isSocket func(string) bool, knownCRISockets []string) (string, error) {
	foundCRISockets := []string{}

	for _, socket := range knownCRISockets {
		if isSocket(socket) {
			foundCRISockets = append(foundCRISockets, socket)
		}
	}

	switch len(foundCRISockets) {
	case 0:
		// Fall back to the default socket if no CRI is detected, we can error out later on if we need it
		return constants.DefaultCRISocket, nil
	case 1:
		// Precisely one CRI found, use that
		return foundCRISockets[0], nil
	default:
		// Multiple CRIs installed?
		return "", errors.Errorf("Found multiple CRI endpoints on the host. Please define which one do you wish "+
			"to use by setting the 'criSocket' field in the kubeadm configuration file: %s",
			strings.Join(foundCRISockets, ", "))
	}
}

// DetectCRISocket uses a list of known CRI sockets to detect one. If more than one or none is discovered, an error is returned.
func DetectCRISocket() (string, error) {
	return detectCRISocketImpl(isExistingSocket, defaultKnownCRISockets)
}