85 lines
2.3 KiB
Go
85 lines
2.3 KiB
Go
package server
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import (
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"heckel.io/ntfy/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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// We want to lock the topic as short as possible, so we make a shallow copy of the
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// subscribers map here. Actually sending out the messages then doesn't have to lock.
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subscribers := t.subscribersCopy()
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if len(subscribers) > 0 {
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log.Debug("%s Forwarding to %d subscriber(s)", logMessagePrefix(v, m), len(subscribers))
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for _, s := range subscribers {
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// We call the subscriber functions in their own Go routines because they are blocking, and
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// we don't want individual slow subscribers to be able to block others.
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go func(s subscriber) {
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if err := s(v, m); err != nil {
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log.Warn("%s Error forwarding to subscriber", logMessagePrefix(v, m))
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}
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}(s)
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}
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} else {
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log.Trace("%s No stream or WebSocket subscribers, not forwarding", logMessagePrefix(v, m))
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}
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}()
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return nil
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}
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// SubscribersCount returns the number of subscribers to this topic
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func (t *topic) SubscribersCount() 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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// subscribersCopy returns a shallow copy of the subscribers map
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func (t *topic) subscribersCopy() map[int]subscriber {
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t.mu.Lock()
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defer t.mu.Unlock()
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subscribers := make(map[int]subscriber)
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for k, v := range t.subscribers {
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subscribers[k] = v
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}
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return subscribers
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}
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