85 lines
1.7 KiB
Go
85 lines
1.7 KiB
Go
package server
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import (
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"context"
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"errors"
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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 int
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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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// message represents a message published to a topic
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type message struct {
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Time int64 `json:"time"`
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Message string `json:"message"`
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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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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) 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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return len(t.subscribers)
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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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if len(t.subscribers) == 0 {
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return errors.New("no subscribers")
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}
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t.last = time.Now()
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t.messages++
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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) 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), 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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