1 /* 2 Copyright 2014 The Kubernetes Authors. 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 "context" 21 "sync" 22 23 "k8s.io/apimachinery/pkg/util/wait" 24 ) 25 26 type merger interface { 27 // Invoked when a change from a source is received. May also function as an incremental 28 // merger if you wish to consume changes incrementally. Must be reentrant when more than 29 // one source is defined. 30 Merge(source string, update interface{}) error 31 } 32 33 // mux is a class for merging configuration from multiple sources. Changes are 34 // pushed via channels and sent to the merge function. 35 type mux struct { 36 // Invoked when an update is sent to a source. 37 merger merger 38 39 // Sources and their lock. 40 sourceLock sync.RWMutex 41 // Maps source names to channels 42 sources map[string]chan interface{} 43 } 44 45 // newMux creates a new mux that can merge changes from multiple sources. 46 func newMux(merger merger) *mux { 47 mux := &mux{ 48 sources: make(map[string]chan interface{}), 49 merger: merger, 50 } 51 return mux 52 } 53 54 // ChannelWithContext returns a channel where a configuration source 55 // can send updates of new configurations. Multiple calls with the same 56 // source will return the same channel. This allows change and state based sources 57 // to use the same channel. Different source names however will be treated as a 58 // union. 59 func (m *mux) ChannelWithContext(ctx context.Context, source string) chan interface{} { 60 if len(source) == 0 { 61 panic("Channel given an empty name") 62 } 63 m.sourceLock.Lock() 64 defer m.sourceLock.Unlock() 65 channel, exists := m.sources[source] 66 if exists { 67 return channel 68 } 69 newChannel := make(chan interface{}) 70 m.sources[source] = newChannel 71 72 go wait.Until(func() { m.listen(source, newChannel) }, 0, ctx.Done()) 73 return newChannel 74 } 75 76 func (m *mux) listen(source string, listenChannel <-chan interface{}) { 77 for update := range listenChannel { 78 m.merger.Merge(source, update) 79 } 80 } 81