redis subscriptions fix

server/router.go

@@ -2,7 +2,6 @@ package server
 
 import (
 	"context"
-	"sync"
 	"time"
 
 	"forge.redroom.link/yves/meowlib"
@@ -205,60 +204,55 @@ func (r *RedisRouter) checkForMessage(msg *meowlib.ToServerMessage) (*meowlib.Fr
 	return &from_server, nil
 }
 
-func goSubscribeAndListen(client *redis.Client, key string, messages chan<- string, wg *sync.WaitGroup, done <-chan struct{}) {
-	defer wg.Done()
-	pubsub := client.Subscribe("msgch:" + key)
-	defer pubsub.Close()
-
-	// Create a new channel for the messages from this subscription
-	myMessages := make(chan *redis.Message)
-	go func() {
-		for {
-			msg, err := pubsub.ReceiveMessage()
-			if err != nil {
-				close(myMessages)
-				return
-			}
-			myMessages <- msg
-		}
-	}()
-
-	// Wait for a message or for the done signal
-	select {
-	case msg := <-myMessages:
-		messages <- msg.Payload
-	case <-done:
-		return
-	}
-}
 
 func (r *RedisRouter) subscribe(msg *meowlib.ToServerMessage, timeout int) (*meowlib.FromServerMessage, error) {
-	var from_server meowlib.FromServerMessage
-	// update messages counter
-	err := r.Client.Incr("statistics:messages:messagessubscription").Err()
+	if err := r.Client.Incr("statistics:messages:messagessubscription").Err(); err != nil {
+		return nil, err
+	}
+
+	channels := make([]string, 0, len(msg.PullRequest))
+	for _, rq := range msg.PullRequest {
+		channels = append(channels, "msgch:"+rq.LookupKey)
+	}
+
+	// Subscribe before re-checking: any publish that fires after Subscribe()
+	// returns is buffered in pubsub.Channel(), closing the store→publish→check race.
+	pubsub := r.Client.Subscribe(channels...)
+	defer pubsub.Close()
+
+	// Drain one subscribe-confirmation per channel.
+	for range len(channels) {
+		if _, err := pubsub.Receive(); err != nil {
+			return nil, err
+		}
+	}
+
+	// Re-check now that we are subscribed; catches messages that arrived
+	// between the caller's first checkForMessage and our Subscribe call.
+	fromServer, err := r.checkForMessage(msg)
 	if err != nil {
 		return nil, err
 	}
-	messages := make(chan string)
-	var wg sync.WaitGroup
-	done := make(chan struct{})
-	// extract lookup keys and subscribe
-	// iterate over pull requests
-	for _, rq := range msg.PullRequest {
-		wg.Add(1)
-		// subscribe to the lookup key
-		go goSubscribeAndListen(r.Client, rq.LookupKey, messages, &wg, done)
+	if len(fromServer.Chat) > 0 || fromServer.Invitation != nil {
+		return fromServer, nil
 	}
-	// wait for timeout or message
+
+	ctx, cancel := context.WithTimeout(r.Context, time.Duration(timeout)*time.Second)
+	defer cancel()
+
+	ch := pubsub.Channel()
 	select {
-	case <-messages:
-		close(done)
+	case <-ctx.Done():
+		if ctx.Err() == context.DeadlineExceeded {
+			return fromServer, nil
+		}
+		return nil, ctx.Err()
+	case _, ok := <-ch:
+		if !ok {
+			return fromServer, nil
+		}
 		return r.checkForMessage(msg)
-	case <-time.After(time.Duration(timeout) * time.Second): // 10 seconds timeout
-		close(done)
 	}
-	wg.Wait()
-	return &from_server, nil
 }
 
 func (r *RedisRouter) handleInvitation(msg *meowlib.ToServerMessage) (*meowlib.FromServerMessage, error) {