585cb83ed0
Backend published auf signage/screen/{slug}/playlist-changed nach
Playlist-Mutationen (2s Debounce). Agent subscribed und fetcht
Playlist sofort (3s Debounce). 60s-Polling bleibt als Fallback.
Neue Packages: mqttnotifier (Backend), mqttsubscriber (Agent)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
117 lines
3.1 KiB
Go
117 lines
3.1 KiB
Go
// Package mqttsubscriber subscribes to playlist-changed MQTT notifications.
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// It is safe for concurrent use and applies client-side debouncing so that
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// a burst of messages within a 3-second window triggers at most one callback.
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package mqttsubscriber
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import (
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"time"
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mqtt "github.com/eclipse/paho.mqtt.golang"
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)
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const (
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// debounceDuration is the minimum interval between two callback invocations.
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// Any MQTT message arriving while the timer is still running resets it.
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debounceDuration = 3 * time.Second
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// playlistChangedTopicTemplate is the topic the backend publishes to.
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playlistChangedTopic = "signage/screen/%s/playlist-changed"
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)
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// PlaylistChangedFunc is called when a debounced playlist-changed notification arrives.
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type PlaylistChangedFunc func()
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// Subscriber listens for playlist-changed notifications on MQTT and calls the
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// provided callback at most once per debounceDuration.
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type Subscriber struct {
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client mqtt.Client
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timer *time.Timer
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onChange PlaylistChangedFunc
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// timerC serializes timer resets through a dedicated goroutine.
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resetC chan struct{}
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stopC chan struct{}
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}
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// Topic returns the MQTT topic for a given screenSlug.
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func Topic(screenSlug string) string {
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return "signage/screen/" + screenSlug + "/playlist-changed"
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}
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// New creates a Subscriber that connects to broker and subscribes to the
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// playlist-changed topic for screenSlug. onChange is called (in its own
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// goroutine) at most once per debounceDuration.
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//
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// Returns nil when broker is empty — callers must handle nil.
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func New(broker, screenSlug, username, password string, onChange PlaylistChangedFunc) *Subscriber {
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if broker == "" {
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return nil
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}
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s := &Subscriber{
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onChange: onChange,
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resetC: make(chan struct{}, 16),
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stopC: make(chan struct{}),
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}
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topic := Topic(screenSlug)
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opts := mqtt.NewClientOptions().
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AddBroker(broker).
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SetClientID("morz-agent-sub-" + screenSlug).
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SetCleanSession(true).
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SetAutoReconnect(true).
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SetConnectRetry(true).
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SetConnectRetryInterval(10 * time.Second).
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SetOnConnectHandler(func(c mqtt.Client) {
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// Re-subscribe after reconnect.
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c.Subscribe(topic, 0, func(_ mqtt.Client, _ mqtt.Message) { //nolint:errcheck
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select {
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case s.resetC <- struct{}{}:
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default: // channel full — debounce timer will fire anyway
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}
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})
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})
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if username != "" {
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opts.SetUsername(username)
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opts.SetPassword(password)
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}
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s.client = mqtt.NewClient(opts)
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s.client.Connect() // non-blocking; paho retries in background
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go s.run()
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return s
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}
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// run is the debounce loop. It resets a timer on every incoming signal.
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// When the timer fires the onChange callback is called once in a goroutine.
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func (s *Subscriber) run() {
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var timer *time.Timer
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for {
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select {
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case <-s.stopC:
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if timer != nil {
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timer.Stop()
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}
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return
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case <-s.resetC:
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if timer != nil {
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timer.Stop()
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}
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timer = time.AfterFunc(debounceDuration, func() {
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go s.onChange()
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})
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}
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}
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}
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// Close disconnects the MQTT client and stops the debounce loop.
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func (s *Subscriber) Close() {
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if s == nil {
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return
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}
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close(s.stopC)
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s.client.Disconnect(250)
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}
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