101 lines
2.0 KiB
Go
101 lines
2.0 KiB
Go
package server
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import (
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"context"
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"log"
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"math/rand"
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"sync"
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"time"
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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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messages []*message
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last time.Time
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ctx context.Context
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cancel context.CancelFunc
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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(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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ctx, cancel := context.WithCancel(context.Background())
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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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last: time.Now(),
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ctx: ctx,
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cancel: cancel,
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}
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}
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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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t.last = time.Now()
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return subscriberID
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}
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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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func (t *topic) Publish(m *message) error {
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t.mu.Lock()
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defer t.mu.Unlock()
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t.last = time.Now()
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t.messages = append(t.messages, m)
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for _, s := range t.subscribers {
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if err := s(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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return nil
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}
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func (t *topic) Messages(since time.Time) []*message {
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t.mu.Lock()
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defer t.mu.Unlock()
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messages := make([]*message, 0) // copy!
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for _, m := range t.messages {
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msgTime := time.Unix(m.Time, 0)
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if msgTime == since || msgTime.After(since) {
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messages = append(messages, m)
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}
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}
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return messages
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}
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func (t *topic) Prune(keep time.Duration) {
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t.mu.Lock()
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defer t.mu.Unlock()
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for i, m := range t.messages {
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msgTime := time.Unix(m.Time, 0)
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if time.Since(msgTime) < keep {
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t.messages = t.messages[i:]
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return
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}
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}
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t.messages = make([]*message, 0)
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}
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func (t *topic) Stats() (subscribers int, messages int) {
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t.mu.Lock()
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defer t.mu.Unlock()
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return len(t.subscribers), len(t.messages)
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}
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func (t *topic) Close() {
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t.cancel()
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}
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