113 lines
2.8 KiB
Go
113 lines
2.8 KiB
Go
package broker
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import (
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"context"
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"fmt"
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"log/slog"
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"net/http"
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"os"
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"time"
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)
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// the amount of time to wait when pushing a message to
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// a slow client or a client that closed after `range clients` started.
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// const patience time.Duration = time.Second * 1
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type (
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NotificationEvent struct {
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EventName string
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Payload string
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}
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NotifierChan chan NotificationEvent
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Broker struct {
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// Events are pushed to this channel by the main events-gathering routine
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Notifier NotifierChan
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log *slog.Logger
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addClient chan NotifierChan
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clients map[NotifierChan]struct{}
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}
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)
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func NewBroker() (broker *Broker) {
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// Instantiate a broker
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return &Broker{
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Notifier: make(NotifierChan, 100),
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log: slog.New(slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{
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Level: slog.LevelDebug,
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AddSource: true,
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})),
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addClient: make(chan NotifierChan, 10),
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clients: map[NotifierChan]struct{}{},
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}
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}
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var Notifier *Broker
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// for use in different packages
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func init() {
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Notifier = NewBroker()
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}
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func (broker *Broker) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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// Headers (keep these as-is)
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w.Header().Set("Content-Type", "text/event-stream")
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w.Header().Set("Cache-Control", "no-cache")
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w.Header().Set("Connection", "keep-alive")
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// w.Header().Set("Access-Control-Allow-Origin", "*")
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origin := r.Header.Get("Origin")
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if origin == "" {
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origin = "*" // Fallback for non-browser clients
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}
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w.Header().Set("Access-Control-Allow-Origin", origin)
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w.Header().Set("Access-Control-Allow-Credentials", "true")
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ctx := r.Context()
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msgChan := make(NotifierChan, 10)
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broker.addClient <- msgChan
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// browser can close sse on its own; ping every 2s to prevent
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heartbeat := time.NewTicker(8 * time.Second)
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defer heartbeat.Stop()
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for {
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select {
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case <-ctx.Done():
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broker.log.Debug("broker: got ctx done")
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// Client disconnected
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return
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case event := <-broker.Notifier:
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broker.log.Debug("got event", "event", event)
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for i := 0; i < 10; i++ { // Repeat 3 times
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_, err := fmt.Fprintf(w, "event: %s\ndata: %s\n\n", event.EventName, event.Payload)
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if err != nil {
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broker.log.Error("write failed", "error", err)
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return
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}
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w.(http.Flusher).Flush()
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// Short delay between sends (non-blocking)
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select {
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case <-time.After(20 * time.Millisecond): // Adjust delay as needed
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case <-ctx.Done():
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return
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}
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}
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case <-heartbeat.C:
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// Send SSE heartbeat comment
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if _, err := fmt.Fprint(w, ":\n\n"); err != nil {
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broker.log.Error("failed to write heartbeat", "error", err)
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return // Client disconnected
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}
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w.(http.Flusher).Flush()
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}
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}
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}
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func (broker *Broker) Listen(ctx context.Context) {
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for {
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select {
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case <-ctx.Done():
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return
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case clientChan := <-broker.addClient:
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// mutex
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broker.clients[clientChan] = struct{}{}
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}
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}
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}
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