1/*
2Copyright 2016 The Kubernetes Authors.
3
4Licensed under the Apache License, Version 2.0 (the "License");
5you may not use this file except in compliance with the License.
6You may obtain a copy of the License at
7
8    http://www.apache.org/licenses/LICENSE-2.0
9
10Unless required by applicable law or agreed to in writing, software
11distributed under the License is distributed on an "AS IS" BASIS,
12WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13See the License for the specific language governing permissions and
14limitations under the License.
15*/
16
17package setdefault
18
19import (
20	"context"
21	"fmt"
22	"io"
23
24	"k8s.io/klog/v2"
25
26	storagev1 "k8s.io/api/storage/v1"
27	"k8s.io/apimachinery/pkg/api/errors"
28	"k8s.io/apimachinery/pkg/labels"
29	"k8s.io/apiserver/pkg/admission"
30	genericadmissioninitializer "k8s.io/apiserver/pkg/admission/initializer"
31	"k8s.io/client-go/informers"
32	storagev1listers "k8s.io/client-go/listers/storage/v1"
33	api "k8s.io/kubernetes/pkg/apis/core"
34	"k8s.io/kubernetes/pkg/apis/core/helper"
35	storageutil "k8s.io/kubernetes/pkg/apis/storage/util"
36)
37
38const (
39	// PluginName is the name of this admission controller plugin
40	PluginName = "DefaultStorageClass"
41)
42
43// Register registers a plugin
44func Register(plugins *admission.Plugins) {
45	plugins.Register(PluginName, func(config io.Reader) (admission.Interface, error) {
46		plugin := newPlugin()
47		return plugin, nil
48	})
49}
50
51// claimDefaulterPlugin holds state for and implements the admission plugin.
52type claimDefaulterPlugin struct {
53	*admission.Handler
54
55	lister storagev1listers.StorageClassLister
56}
57
58var _ admission.Interface = &claimDefaulterPlugin{}
59var _ admission.MutationInterface = &claimDefaulterPlugin{}
60var _ = genericadmissioninitializer.WantsExternalKubeInformerFactory(&claimDefaulterPlugin{})
61
62// newPlugin creates a new admission plugin.
63func newPlugin() *claimDefaulterPlugin {
64	return &claimDefaulterPlugin{
65		Handler: admission.NewHandler(admission.Create),
66	}
67}
68
69func (a *claimDefaulterPlugin) SetExternalKubeInformerFactory(f informers.SharedInformerFactory) {
70	informer := f.Storage().V1().StorageClasses()
71	a.lister = informer.Lister()
72	a.SetReadyFunc(informer.Informer().HasSynced)
73}
74
75// ValidateInitialization ensures lister is set.
76func (a *claimDefaulterPlugin) ValidateInitialization() error {
77	if a.lister == nil {
78		return fmt.Errorf("missing lister")
79	}
80	return nil
81}
82
83// Admit sets the default value of a PersistentVolumeClaim's storage class, in case the user did
84// not provide a value.
85//
86// 1.  Find available StorageClasses.
87// 2.  Figure which is the default
88// 3.  Write to the PVClaim
89func (a *claimDefaulterPlugin) Admit(ctx context.Context, attr admission.Attributes, o admission.ObjectInterfaces) error {
90	if attr.GetResource().GroupResource() != api.Resource("persistentvolumeclaims") {
91		return nil
92	}
93
94	if len(attr.GetSubresource()) != 0 {
95		return nil
96	}
97
98	pvc, ok := attr.GetObject().(*api.PersistentVolumeClaim)
99	// if we can't convert then we don't handle this object so just return
100	if !ok {
101		return nil
102	}
103
104	if helper.PersistentVolumeClaimHasClass(pvc) {
105		// The user asked for a class.
106		return nil
107	}
108
109	klog.V(4).Infof("no storage class for claim %s (generate: %s)", pvc.Name, pvc.GenerateName)
110
111	def, err := getDefaultClass(a.lister)
112	if err != nil {
113		return admission.NewForbidden(attr, err)
114	}
115	if def == nil {
116		// No default class selected, do nothing about the PVC.
117		return nil
118	}
119
120	klog.V(4).Infof("defaulting storage class for claim %s (generate: %s) to %s", pvc.Name, pvc.GenerateName, def.Name)
121	pvc.Spec.StorageClassName = &def.Name
122	return nil
123}
124
125// getDefaultClass returns the default StorageClass from the store, or nil.
126func getDefaultClass(lister storagev1listers.StorageClassLister) (*storagev1.StorageClass, error) {
127	list, err := lister.List(labels.Everything())
128	if err != nil {
129		return nil, err
130	}
131
132	defaultClasses := []*storagev1.StorageClass{}
133	for _, class := range list {
134		if storageutil.IsDefaultAnnotation(class.ObjectMeta) {
135			defaultClasses = append(defaultClasses, class)
136			klog.V(4).Infof("getDefaultClass added: %s", class.Name)
137		}
138	}
139
140	if len(defaultClasses) == 0 {
141		return nil, nil
142	}
143	if len(defaultClasses) > 1 {
144		klog.V(4).Infof("getDefaultClass %d defaults found", len(defaultClasses))
145		return nil, errors.NewInternalError(fmt.Errorf("%d default StorageClasses were found", len(defaultClasses)))
146	}
147	return defaultClasses[0], nil
148}
149