mq(kafka): debug Metadata v1 format compatibility with kafka-go ReadPartitions

- Added detailed hex dump comparison between v0 and v1 responses
- Identified v1 adds rack field (2 bytes) and is_internal field (1 byte) = 3 bytes total
- kafka-go still fails with 'multiple Read calls return no data or error'
- Our Metadata v1 format appears correct per protocol spec but incompatible with kafka-go

test/kafka/connection_debug_test.go

@@ -0,0 +1,95 @@
+package kafka
+
+import (
+	"fmt"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/segmentio/kafka-go"
+	"github.com/seaweedfs/seaweedfs/weed/mq/kafka/gateway"
+)
+
+// TestConnectionDebug debugs the exact connection behavior between kafka-go and our gateway
+func TestConnectionDebug(t *testing.T) {
+	// Start gateway server
+	gatewayServer := gateway.NewServer(gateway.Options{
+		Listen: ":0", // random port
+	})
+
+	go func() {
+		if err := gatewayServer.Start(); err != nil {
+			t.Errorf("Gateway server error: %v", err)
+		}
+	}()
+	defer gatewayServer.Close()
+
+	// Wait for server to start
+	time.Sleep(100 * time.Millisecond)
+
+	// Get the actual listening address
+	host, port := gatewayServer.GetListenerAddr()
+	brokerAddr := fmt.Sprintf("%s:%d", host, port)
+	t.Logf("Gateway running on %s", brokerAddr)
+
+	// Get handler and configure it
+	handler := gatewayServer.GetHandler()
+	handler.SetBrokerAddress(host, port)
+
+	// Add test topic
+	topicName := "conn-debug-topic"
+	handler.AddTopicForTesting(topicName, 1)
+
+	// Test 1: Manual connection that works
+	t.Log("=== Test 1: Manual TCP connection ===")
+	conn, err := net.Dial("tcp", brokerAddr)
+	if err != nil {
+		t.Fatalf("Manual connection failed: %v", err)
+	}
+	
+	// Send a simple request and read response
+	// This should work based on our previous debug test
+	conn.Close()
+	t.Log("Manual connection works fine")
+
+	// Test 2: kafka-go Dialer connection
+	t.Log("=== Test 2: kafka-go Dialer connection ===")
+	dialer := &kafka.Dialer{
+		Timeout: 5 * time.Second,
+	}
+	
+	kafkaConn, err := dialer.Dial("tcp", brokerAddr)
+	if err != nil {
+		t.Fatalf("kafka-go connection failed: %v", err)
+	}
+	defer kafkaConn.Close()
+	
+	t.Log("kafka-go connection established")
+
+	// Test 3: Try to read partitions with detailed error handling
+	t.Log("=== Test 3: kafka-go ReadPartitions with error details ===")
+	
+	// Set a deadline to avoid hanging
+	kafkaConn.SetDeadline(time.Now().Add(10 * time.Second))
+	
+	partitions, err := kafkaConn.ReadPartitions(topicName)
+	if err != nil {
+		t.Logf("ReadPartitions failed with error: %v", err)
+		t.Logf("Error type: %T", err)
+		
+		// Try to get more details about the error
+		if netErr, ok := err.(net.Error); ok {
+			t.Logf("Network error - Timeout: %v, Temporary: %v", netErr.Timeout(), netErr.Temporary())
+		}
+		
+		// The error might give us clues about what's wrong
+		return
+	}
+
+	t.Logf("ReadPartitions succeeded! Found %d partitions", len(partitions))
+	for i, partition := range partitions {
+		t.Logf("Partition %d: Topic=%s, ID=%d, Leader=%v", i, partition.Topic, partition.ID, partition.Leader)
+	}
+
+	t.Log("✅ Connection debug test completed!")
+}