k8s.io/kubernetes@v1.29.3/pkg/util/config/config.go (about)

     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  // MergeFunc implements the Merger interface
    34  type MergeFunc func(source string, update interface{}) error
    35  
    36  func (f MergeFunc) Merge(source string, update interface{}) error {
    37  	return f(source, update)
    38  }
    39  
    40  // Mux is a class for merging configuration from multiple sources.  Changes are
    41  // pushed via channels and sent to the merge function.
    42  type Mux struct {
    43  	// Invoked when an update is sent to a source.
    44  	merger Merger
    45  
    46  	// Sources and their lock.
    47  	sourceLock sync.RWMutex
    48  	// Maps source names to channels
    49  	sources map[string]chan interface{}
    50  }
    51  
    52  // NewMux creates a new mux that can merge changes from multiple sources.
    53  func NewMux(merger Merger) *Mux {
    54  	mux := &Mux{
    55  		sources: make(map[string]chan interface{}),
    56  		merger:  merger,
    57  	}
    58  	return mux
    59  }
    60  
    61  // ChannelWithContext returns a channel where a configuration source
    62  // can send updates of new configurations. Multiple calls with the same
    63  // source will return the same channel. This allows change and state based sources
    64  // to use the same channel. Different source names however will be treated as a
    65  // union.
    66  func (m *Mux) ChannelWithContext(ctx context.Context, source string) chan interface{} {
    67  	if len(source) == 0 {
    68  		panic("Channel given an empty name")
    69  	}
    70  	m.sourceLock.Lock()
    71  	defer m.sourceLock.Unlock()
    72  	channel, exists := m.sources[source]
    73  	if exists {
    74  		return channel
    75  	}
    76  	newChannel := make(chan interface{})
    77  	m.sources[source] = newChannel
    78  
    79  	go wait.Until(func() { m.listen(source, newChannel) }, 0, ctx.Done())
    80  	return newChannel
    81  }
    82  
    83  func (m *Mux) listen(source string, listenChannel <-chan interface{}) {
    84  	for update := range listenChannel {
    85  		m.merger.Merge(source, update)
    86  	}
    87  }
    88  
    89  // Accessor is an interface for retrieving the current merge state.
    90  type Accessor interface {
    91  	// MergedState returns a representation of the current merge state.
    92  	// Must be reentrant when more than one source is defined.
    93  	MergedState() interface{}
    94  }
    95  
    96  // AccessorFunc implements the Accessor interface.
    97  type AccessorFunc func() interface{}
    98  
    99  func (f AccessorFunc) MergedState() interface{} {
   100  	return f()
   101  }
   102  
   103  type Listener interface {
   104  	// OnUpdate is invoked when a change is made to an object.
   105  	OnUpdate(instance interface{})
   106  }
   107  
   108  // ListenerFunc receives a representation of the change or object.
   109  type ListenerFunc func(instance interface{})
   110  
   111  func (f ListenerFunc) OnUpdate(instance interface{}) {
   112  	f(instance)
   113  }
   114  
   115  type Broadcaster struct {
   116  	// Listeners for changes and their lock.
   117  	listenerLock sync.RWMutex
   118  	listeners    []Listener
   119  }
   120  
   121  // NewBroadcaster registers a set of listeners that support the Listener interface
   122  // and notifies them all on changes.
   123  func NewBroadcaster() *Broadcaster {
   124  	return &Broadcaster{}
   125  }
   126  
   127  // Add registers listener to receive updates of changes.
   128  func (b *Broadcaster) Add(listener Listener) {
   129  	b.listenerLock.Lock()
   130  	defer b.listenerLock.Unlock()
   131  	b.listeners = append(b.listeners, listener)
   132  }
   133  
   134  // Notify notifies all listeners.
   135  func (b *Broadcaster) Notify(instance interface{}) {
   136  	b.listenerLock.RLock()
   137  	listeners := b.listeners
   138  	b.listenerLock.RUnlock()
   139  	for _, listener := range listeners {
   140  		listener.OnUpdate(instance)
   141  	}
   142  }