mq(kafka): Major debugging progress on Metadata v7 compatibility

BREAKTHROUGH DISCOVERIES:
✅ Performance issue SOLVED: Debug logging was causing 6.8s delays → now 20μs
✅ Metadata v7 format partially working: kafka-go accepts response (no disconnect)
✅ kafka-go workflow confirmed: Never calls Produce API - validates Metadata first

CURRENT ISSUE IDENTIFIED:
❌ kafka-go validates Metadata response → returns '[3] Unknown Topic Or Partition'
❌ Error comes from kafka-go's internal validation, not our API handlers
❌ kafka-go retries with more Metadata requests (normal retry behavior)

DEBUGGING IMPLEMENTED:
- Added comprehensive API request logging to confirm request flow
- Added detailed Produce API debugging (unused but ready)
- Added Metadata response hex dumps for format validation
- Confirmed no unsupported API calls being made

METADATA V7 COMPLIANCE:
✅ Added cluster authorized operations field
✅ Added topic UUID fields (16-byte null UUID)
✅ Added is_internal_topic field
✅ Added topic authorized operations field
✅ Response format appears correct (120 bytes)

NEXT: Debug why kafka-go rejects our otherwise well-formed Metadata v7 response.
Likely broker address mismatch, partition state issue, or missing v7 field.

test/kafka/api_sequence_test.go

@@ -0,0 +1,67 @@
+package kafka
+
+import (
+	"context"
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/seaweedfs/seaweedfs/weed/mq/kafka/gateway"
+	"github.com/segmentio/kafka-go"
+)
+
+// TestKafkaGateway_APISequence logs all API requests that kafka-go makes
+func TestKafkaGateway_APISequence(t *testing.T) {
+	// Start the gateway server
+	srv := gateway.NewServer(gateway.Options{
+		Listen:       ":0",
+		UseSeaweedMQ: false,
+	})
+
+	if err := srv.Start(); err != nil {
+		t.Fatalf("Failed to start gateway: %v", err)
+	}
+	defer srv.Close()
+
+	brokerAddr := srv.Addr()
+	t.Logf("Gateway running on %s", brokerAddr)
+
+	// Pre-create topic
+	topicName := "api-sequence-topic"
+	handler := srv.GetHandler()
+	handler.AddTopicForTesting(topicName, 1)
+
+	// Create a writer and try to write a single message
+	writer := &kafka.Writer{
+		Addr:         kafka.TCP(brokerAddr),
+		Topic:        topicName,
+		WriteTimeout: 15 * time.Second,
+		ReadTimeout:  15 * time.Second,
+		Logger: kafka.LoggerFunc(func(msg string, args ...interface{}) {
+			fmt.Printf("KAFKA-GO WRITER LOG: "+msg+"\n", args...)
+		}),
+		ErrorLogger: kafka.LoggerFunc(func(msg string, args ...interface{}) {
+			fmt.Printf("KAFKA-GO WRITER ERROR: "+msg+"\n", args...)
+		}),
+	}
+	defer writer.Close()
+
+	// Try to write a single message and log the full API sequence
+	ctx, cancel := context.WithTimeout(context.Background(), 12*time.Second)
+	defer cancel()
+
+	fmt.Printf("\n=== STARTING kafka-go WRITE ATTEMPT ===\n")
+
+	err := writer.WriteMessages(ctx, kafka.Message{
+		Key:   []byte("test-key"),
+		Value: []byte("test-value"),
+	})
+
+	fmt.Printf("\n=== kafka-go WRITE COMPLETED ===\n")
+
+	if err != nil {
+		t.Logf("WriteMessages result: %v", err)
+	} else {
+		t.Logf("WriteMessages succeeded!")
+	}
+}

test/kafka/produce_consume_test.go

@@ -90,16 +90,16 @@ func createTopicDirectly(srv interface{}, topicName string) error {
 	if !ok {
 		return fmt.Errorf("invalid server type")
 	}
-	
+
 	// Get the handler and directly add the topic
 	handler := gatewayServer.GetHandler()
 	if handler == nil {
 		return fmt.Errorf("handler is nil")
 	}
-	
+
 	// Add the topic with 1 partition
 	handler.AddTopicForTesting(topicName, 1)
-	
+
 	fmt.Printf("DEBUG: Topic %s created directly in handler registry\n", topicName)
 	return nil
 }
@@ -111,9 +111,9 @@ func produceMessagesDirect(brokerAddr, topicName string, messages []kafka.Messag
 		Topic:    topicName,
 		Balancer: &kafka.LeastBytes{},
 
-		// Reduce timeouts for faster debugging
-		WriteTimeout: 10 * time.Second,
-		ReadTimeout:  10 * time.Second,
+		// Increase timeouts to see if kafka-go eventually makes other requests
+		WriteTimeout: 20 * time.Second,
+		ReadTimeout:  20 * time.Second,
 
 		// Enable detailed logging
 		Logger: kafka.LoggerFunc(func(msg string, args ...interface{}) {