我有一个用java写的Kafka制作人。尽管它基本上只是一个简单的示例代码，但它似乎并不能正常工作。我希望输出10条消息到我的集群。相反，我得到了消息successful output，但实际上没有任何东西进入集群。我不确定从哪里开始排除故障。

import java.util.Properties;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerRecord;

public class SimpleProducer {

 public static void main(String[] args) throws Exception{

    String topicName = "test_topic";
    Properties props = new Properties();
    props.put("bootstrap.servers", "skynet.local:6667");    
    props.put("acks", "all");
    props.put("retries", 0);
    props.put("batch.size", 16384);   
    props.put("linger.ms", 1);   
    props.put("buffer.memory", 33554432);
    props.put("key.serializer","org.apache.kafka.common.serialization.StringSerializer");
    props.put("value.serializer","org.apache.kafka.common.serialization.StringSerializer");

    Producer<String, String> producer = new KafkaProducer<String, String>(props);

    for(int i = 0; i < 10; i++)
       producer.send(new ProducerRecord<String, String>(topicName, Integer.toString(i), Integer.toString(i)));
       System.out.println("Message sent successfully");
       producer.close();
 }
}