mount_pod.go

/*
Copyright 2017 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 mountpod

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"os"
	"path"

	"k8s.io/api/core/v1"
	"k8s.io/kubernetes/pkg/kubelet/config"
	kubepod "k8s.io/kubernetes/pkg/kubelet/pod"
	"k8s.io/kubernetes/pkg/util/strings"
)

// Manager is an interface that tracks pods with mount utilities for individual
// volume plugins.
type Manager interface {
	GetMountPod(pluginName string) (pod *v1.Pod, container string, err error)
}

// basicManager is simple implementation of Manager. Pods with mount utilities
// are registered by placing a JSON file into
// /var/lib/kubelet/plugin-containers/<plugin name>.json and this manager just
// finds them there.
type basicManager struct {
	registrationDirectory string
	podManager            kubepod.Manager
}

// volumePluginRegistration specified format of the json files placed in
// /var/lib/kubelet/plugin-containers/
type volumePluginRegistration struct {
	PodName       string `json:"podName"`
	PodNamespace  string `json:"podNamespace"`
	PodUID        string `json:"podUID"`
	ContainerName string `json:"containerName"`
}

// NewManager returns a new mount pod manager.
func NewManager(rootDirectory string, podManager kubepod.Manager) (Manager, error) {
	regPath := path.Join(rootDirectory, config.DefaultKubeletPluginContainersDirName)

	// Create the directory on startup
	os.MkdirAll(regPath, 0700)

	return &basicManager{
		registrationDirectory: regPath,
		podManager:            podManager,
	}, nil
}

func (m *basicManager) getVolumePluginRegistrationPath(pluginName string) string {
	// sanitize plugin name so it does not escape directory
	safePluginName := strings.EscapePluginName(pluginName) + ".json"
	return path.Join(m.registrationDirectory, safePluginName)
}

func (m *basicManager) GetMountPod(pluginName string) (pod *v1.Pod, containerName string, err error) {
	// Read /var/lib/kubelet/plugin-containers/<plugin name>.json
	regPath := m.getVolumePluginRegistrationPath(pluginName)
	regBytes, err := ioutil.ReadFile(regPath)
	if err != nil {
		if os.IsNotExist(err) {
			// No pod is registered for this plugin
			return nil, "", nil
		}
		return nil, "", fmt.Errorf("cannot read %s: %v", regPath, err)
	}

	// Parse json
	var reg volumePluginRegistration
	if err := json.Unmarshal(regBytes, &reg); err != nil {
		return nil, "", fmt.Errorf("unable to parse %s: %s", regPath, err)
	}
	if len(reg.ContainerName) == 0 {
		return nil, "", fmt.Errorf("unable to parse %s: \"containerName\" is not set", regPath)
	}
	if len(reg.PodUID) == 0 {
		return nil, "", fmt.Errorf("unable to parse %s: \"podUID\" is not set", regPath)
	}
	if len(reg.PodNamespace) == 0 {
		return nil, "", fmt.Errorf("unable to parse %s: \"podNamespace\" is not set", regPath)
	}
	if len(reg.PodName) == 0 {
		return nil, "", fmt.Errorf("unable to parse %s: \"podName\" is not set", regPath)
	}

	pod, ok := m.podManager.GetPodByName(reg.PodNamespace, reg.PodName)
	if !ok {
		return nil, "", fmt.Errorf("unable to process %s: pod %s/%s not found", regPath, reg.PodNamespace, reg.PodName)
	}
	if string(pod.UID) != reg.PodUID {
		return nil, "", fmt.Errorf("unable to process %s: pod %s/%s has unexpected UID", regPath, reg.PodNamespace, reg.PodName)
	}
	// make sure that reg.ContainerName exists in the pod
	for i := range pod.Spec.Containers {
		if pod.Spec.Containers[i].Name == reg.ContainerName {
			return pod, reg.ContainerName, nil
		}
	}
	return nil, "", fmt.Errorf("unable to process %s: pod %s/%s has no container named %q", regPath, reg.PodNamespace, reg.PodName, reg.ContainerName)

}