github.com/timstclair/heapster@v0.20.0-alpha1/Godeps/_workspace/src/k8s.io/kubernetes/pkg/util/config/config.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 config 18 19 import ( 20 "sync" 21 22 "k8s.io/kubernetes/pkg/util" 23 ) 24 25 type Merger interface { 26 // Invoked when a change from a source is received. May also function as an incremental 27 // merger if you wish to consume changes incrementally. Must be reentrant when more than 28 // one source is defined. 29 Merge(source string, update interface{}) error 30 } 31 32 // MergeFunc implements the Merger interface 33 type MergeFunc func(source string, update interface{}) error 34 35 func (f MergeFunc) Merge(source string, update interface{}) error { 36 return f(source, update) 37 } 38 39 // Mux is a class for merging configuration from multiple sources. Changes are 40 // pushed via channels and sent to the merge function. 41 type Mux struct { 42 // Invoked when an update is sent to a source. 43 merger Merger 44 45 // Sources and their lock. 46 sourceLock sync.RWMutex 47 // Maps source names to channels 48 sources map[string]chan interface{} 49 } 50 51 // NewMux creates a new mux that can merge changes from multiple sources. 52 func NewMux(merger Merger) *Mux { 53 mux := &Mux{ 54 sources: make(map[string]chan interface{}), 55 merger: merger, 56 } 57 return mux 58 } 59 60 // Channel returns a channel where a configuration source 61 // can send updates of new configurations. Multiple calls with the same 62 // source will return the same channel. This allows change and state based sources 63 // to use the same channel. Different source names however will be treated as a 64 // union. 65 func (m *Mux) Channel(source string) chan interface{} { 66 if len(source) == 0 { 67 panic("Channel given an empty name") 68 } 69 m.sourceLock.Lock() 70 defer m.sourceLock.Unlock() 71 channel, exists := m.sources[source] 72 if exists { 73 return channel 74 } 75 newChannel := make(chan interface{}) 76 m.sources[source] = newChannel 77 go util.Until(func() { m.listen(source, newChannel) }, 0, util.NeverStop) 78 return newChannel 79 } 80 81 func (m *Mux) listen(source string, listenChannel <-chan interface{}) { 82 for update := range listenChannel { 83 m.merger.Merge(source, update) 84 } 85 } 86 87 // Accessor is an interface for retrieving the current merge state. 88 type Accessor interface { 89 // MergedState returns a representation of the current merge state. 90 // Must be reentrant when more than one source is defined. 91 MergedState() interface{} 92 } 93 94 // AccessorFunc implements the Accessor interface. 95 type AccessorFunc func() interface{} 96 97 func (f AccessorFunc) MergedState() interface{} { 98 return f() 99 } 100 101 type Listener interface { 102 // OnUpdate is invoked when a change is made to an object. 103 OnUpdate(instance interface{}) 104 } 105 106 // ListenerFunc receives a representation of the change or object. 107 type ListenerFunc func(instance interface{}) 108 109 func (f ListenerFunc) OnUpdate(instance interface{}) { 110 f(instance) 111 } 112 113 type Broadcaster struct { 114 // Listeners for changes and their lock. 115 listenerLock sync.RWMutex 116 listeners []Listener 117 } 118 119 // NewBroadcaster registers a set of listeners that support the Listener interface 120 // and notifies them all on changes. 121 func NewBroadcaster() *Broadcaster { 122 return &Broadcaster{} 123 } 124 125 // Add registers listener to receive updates of changes. 126 func (b *Broadcaster) Add(listener Listener) { 127 b.listenerLock.Lock() 128 defer b.listenerLock.Unlock() 129 b.listeners = append(b.listeners, listener) 130 } 131 132 // Notify notifies all listeners. 133 func (b *Broadcaster) Notify(instance interface{}) { 134 b.listenerLock.RLock() 135 listeners := b.listeners 136 b.listenerLock.RUnlock() 137 for _, listener := range listeners { 138 listener.OnUpdate(instance) 139 } 140 }