155 lines
3.2 KiB
Go
155 lines
3.2 KiB
Go
package events
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import (
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"strings"
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"sync"
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"github.com/apex/log"
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)
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type Listener chan Event
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// Event represents an Event sent over a Bus.
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type Event struct {
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Topic string
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Data interface{}
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}
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// Bus represents an Event Bus.
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type Bus struct {
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listenersMx sync.Mutex
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listeners map[string][]Listener
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}
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// NewBus returns a new empty Event Bus.
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func NewBus() *Bus {
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return &Bus{
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listeners: make(map[string][]Listener),
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}
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}
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// Off unregisters a listener from the specified topics on the Bus.
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func (b *Bus) Off(listener Listener, topics ...string) {
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b.listenersMx.Lock()
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defer b.listenersMx.Unlock()
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var closed bool
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for _, topic := range topics {
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ok := b.off(topic, listener)
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if !closed && ok {
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log.Debug("closing event channel!")
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close(listener)
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closed = true
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}
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}
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}
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func (b *Bus) off(topic string, listener Listener) bool {
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listeners, ok := b.listeners[topic]
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if !ok {
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return false
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}
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for i, l := range listeners {
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if l != listener {
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continue
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}
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listeners = append(listeners[:i], listeners[i+1:]...)
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b.listeners[topic] = listeners
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return true
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}
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return false
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}
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// On registers a listener to the specified topics on the Bus.
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func (b *Bus) On(listener Listener, topics ...string) {
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b.listenersMx.Lock()
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defer b.listenersMx.Unlock()
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for _, topic := range topics {
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b.on(topic, listener)
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}
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}
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func (b *Bus) on(topic string, listener Listener) {
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listeners, ok := b.listeners[topic]
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if !ok {
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b.listeners[topic] = []Listener{listener}
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} else {
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b.listeners[topic] = append(listeners, listener)
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}
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}
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// Publish publishes a message to the Bus.
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func (b *Bus) Publish(topic string, data interface{}) {
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// Some of our topics for the socket support passing a more specific namespace,
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// such as "backup completed:1234" to indicate which specific backup was completed.
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//
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// In these cases, we still need to send the event using the standard listener
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// name of "backup completed".
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if strings.Contains(topic, ":") {
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parts := strings.SplitN(topic, ":", 2)
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if len(parts) == 2 {
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topic = parts[0]
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}
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}
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b.listenersMx.Lock()
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defer b.listenersMx.Unlock()
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listeners, ok := b.listeners[topic]
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if !ok {
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return
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}
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if len(listeners) < 1 {
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return
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}
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var wg sync.WaitGroup
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event := Event{Topic: topic, Data: data}
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for _, listener := range listeners {
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l := listener
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wg.Add(1)
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go func(l Listener, event Event) {
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defer wg.Done()
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l <- event
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}(l, event)
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}
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wg.Wait()
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}
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// Destroy destroys the Event Bus by unregistering and closing all listeners.
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func (b *Bus) Destroy() {
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b.listenersMx.Lock()
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defer b.listenersMx.Unlock()
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// Track what listeners have already been closed. Because the same listener
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// can be listening on multiple topics, we need a way to essentially
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// "de-duplicate" all the listeners across all the topics.
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var closed []Listener
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for _, listeners := range b.listeners {
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for _, listener := range listeners {
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if contains(closed, listener) {
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continue
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}
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close(listener)
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closed = append(closed, listener)
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}
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}
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b.listeners = make(map[string][]Listener)
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}
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func contains(closed []Listener, listener Listener) bool {
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for _, c := range closed {
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if c == listener {
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return true
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}
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}
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return false
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}
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