63 lines
1.4 KiB
Go
63 lines
1.4 KiB
Go
package server
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import (
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"log"
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"math/rand"
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"sync"
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)
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// topic represents a channel to which subscribers can subscribe, and publishers
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// can publish a message
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type topic struct {
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ID string
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subscribers map[int]subscriber
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mu sync.Mutex
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}
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// subscriber is a function that is called for every new message on a topic
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type subscriber func(v *visitor, msg *message) error
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// newTopic creates a new topic
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func newTopic(id string) *topic {
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return &topic{
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ID: id,
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subscribers: make(map[int]subscriber),
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}
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}
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// Subscribe subscribes to this topic
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func (t *topic) Subscribe(s subscriber) int {
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t.mu.Lock()
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defer t.mu.Unlock()
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subscriberID := rand.Int()
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t.subscribers[subscriberID] = s
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return subscriberID
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}
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// Unsubscribe removes the subscription from the list of subscribers
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func (t *topic) Unsubscribe(id int) {
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t.mu.Lock()
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defer t.mu.Unlock()
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delete(t.subscribers, id)
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}
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// Publish asynchronously publishes to all subscribers
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func (t *topic) Publish(v *visitor, m *message) error {
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go func() {
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t.mu.Lock()
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defer t.mu.Unlock()
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for _, s := range t.subscribers {
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if err := s(v, m); err != nil {
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log.Printf("error publishing message to subscriber")
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}
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}
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}()
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return nil
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}
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// Subscribers returns the number of subscribers to this topic
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func (t *topic) Subscribers() int {
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t.mu.Lock()
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defer t.mu.Unlock()
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return len(t.subscribers)
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}
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