Update fetch.go

Skip long-polling if any requested topic does not exist.
Only long-poll when MinBytes > 0, data isn’t available yet, and all topics exist.
Cap the long-polling wait to 1s in tests to prevent hanging on shutdown.

weed/mq/kafka/protocol/fetch.go

@@ -22,6 +22,15 @@ func (h *Handler) handleFetch(correlationID uint32, apiVersion uint16, requestBo
 
 	// Basic long-polling to avoid client busy-looping when there's no data.
 	var throttleTimeMs int32 = 0
+	// Only long-poll when all referenced topics exist; unknown topics should not block
+	allTopicsExist := func() bool {
+		for _, topic := range fetchRequest.Topics {
+			if !h.seaweedMQHandler.TopicExists(topic.Name) {
+				return false
+			}
+		}
+		return true
+	}
 	hasDataAvailable := func() bool {
 		for _, topic := range fetchRequest.Topics {
 			for _, p := range topic.Partitions {
@@ -36,9 +45,15 @@ func (h *Handler) handleFetch(correlationID uint32, apiVersion uint16, requestBo
 		}
 		return false
 	}
-	if fetchRequest.MinBytes > 0 && fetchRequest.MaxWaitTime > 0 && !hasDataAvailable() {
+	// Cap long-polling to avoid blocking connection shutdowns in tests
+	maxWaitMs := fetchRequest.MaxWaitTime
+	if maxWaitMs > 1000 {
+		maxWaitMs = 1000
+	}
+	shouldLongPoll := fetchRequest.MinBytes > 0 && maxWaitMs > 0 && !hasDataAvailable() && allTopicsExist()
+	if shouldLongPoll {
 		start := time.Now()
-		deadline := start.Add(time.Duration(fetchRequest.MaxWaitTime) * time.Millisecond)
+		deadline := start.Add(time.Duration(maxWaitMs) * time.Millisecond)
 		for time.Now().Before(deadline) {
 			time.Sleep(10 * time.Millisecond)
 			if hasDataAvailable() {