github.com/timstclair/heapster@v0.20.0-alpha1/Godeps/_workspace/src/k8s.io/kubernetes/pkg/api/context.go (about) 1 /* 2 Copyright 2014 The Kubernetes Authors All rights reserved. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 package api 18 19 import ( 20 stderrs "errors" 21 "time" 22 23 "golang.org/x/net/context" 24 "k8s.io/kubernetes/pkg/auth/user" 25 ) 26 27 // Context carries values across API boundaries. 28 // This context matches the context.Context interface 29 // (https://blog.golang.org/context), for the purposes 30 // of passing the api.Context through to the storage tier. 31 // TODO: Determine the extent that this abstraction+interface 32 // is used by the api, and whether we can remove. 33 type Context interface { 34 // Value returns the value associated with key or nil if none. 35 Value(key interface{}) interface{} 36 37 // Deadline returns the time when this Context will be canceled, if any. 38 Deadline() (deadline time.Time, ok bool) 39 40 // Done returns a channel that is closed when this Context is canceled 41 // or times out. 42 Done() <-chan struct{} 43 44 // Err indicates why this context was canceled, after the Done channel 45 // is closed. 46 Err() error 47 } 48 49 // The key type is unexported to prevent collisions 50 type key int 51 52 // namespaceKey is the context key for the request namespace. 53 const namespaceKey key = 0 54 55 // userKey is the context key for the request user. 56 const userKey key = 1 57 58 // NewContext instantiates a base context object for request flows. 59 func NewContext() Context { 60 return context.TODO() 61 } 62 63 // NewDefaultContext instantiates a base context object for request flows in the default namespace 64 func NewDefaultContext() Context { 65 return WithNamespace(NewContext(), NamespaceDefault) 66 } 67 68 // WithValue returns a copy of parent in which the value associated with key is val. 69 func WithValue(parent Context, key interface{}, val interface{}) Context { 70 internalCtx, ok := parent.(context.Context) 71 if !ok { 72 panic(stderrs.New("Invalid context type")) 73 } 74 return context.WithValue(internalCtx, key, val) 75 } 76 77 // WithNamespace returns a copy of parent in which the namespace value is set 78 func WithNamespace(parent Context, namespace string) Context { 79 return WithValue(parent, namespaceKey, namespace) 80 } 81 82 // NamespaceFrom returns the value of the namespace key on the ctx 83 func NamespaceFrom(ctx Context) (string, bool) { 84 namespace, ok := ctx.Value(namespaceKey).(string) 85 return namespace, ok 86 } 87 88 // NamespaceValue returns the value of the namespace key on the ctx, or the empty string if none 89 func NamespaceValue(ctx Context) string { 90 namespace, _ := NamespaceFrom(ctx) 91 return namespace 92 } 93 94 // ValidNamespace returns false if the namespace on the context differs from the resource. If the resource has no namespace, it is set to the value in the context. 95 func ValidNamespace(ctx Context, resource *ObjectMeta) bool { 96 ns, ok := NamespaceFrom(ctx) 97 if len(resource.Namespace) == 0 { 98 resource.Namespace = ns 99 } 100 return ns == resource.Namespace && ok 101 } 102 103 // WithNamespaceDefaultIfNone returns a context whose namespace is the default if and only if the parent context has no namespace value 104 func WithNamespaceDefaultIfNone(parent Context) Context { 105 namespace, ok := NamespaceFrom(parent) 106 if !ok || len(namespace) == 0 { 107 return WithNamespace(parent, NamespaceDefault) 108 } 109 return parent 110 } 111 112 // WithUser returns a copy of parent in which the user value is set 113 func WithUser(parent Context, user user.Info) Context { 114 return WithValue(parent, userKey, user) 115 } 116 117 // UserFrom returns the value of the user key on the ctx 118 func UserFrom(ctx Context) (user.Info, bool) { 119 user, ok := ctx.Value(userKey).(user.Info) 120 return user, ok 121 }