kafka-java使用的一些坑

1、pruducer未关闭，或者main线程关闭太快，会导致producer生成者的消息并未完全发送给kafka

以下代码显示了，如果当前producer发送失败，则需要隔一段时间才会有数字打印出来

import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;

import java.util.Properties;

/*
* A Kafka client that publishes records to the Kafka cluster.
The producer is thread safe and sharing a single producer instance across threads will generally be faster than having multiple instances.

Here is a simple example of using the producer to send records with strings containing sequential numbers as the key/value pairs.
*/
public class KafkaProducerTest3 {
    private static Producer producer = null;
    static {
        Properties props = new Properties();
        props.put("bootstrap.servers", "localhost:9092");
        props.put("acks", "all");
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        producer = new  KafkaProducer(props);
    }

     public static void sendMsg(String topic,String value){
        producer.send(new ProducerRecord<>(topic,value));
        // producer.close();
    }


    public static void main(String[] args) {
        // 这样直接发送数据会造成问题，kafka并没有接收到数据，因为主线程关闭太快
        for (int i = 0; i < 1000; i++) {
            sendMsg("dd","fffffff");
            System.out.println(i);
        }
        // 加上主线程耗时，或者while true 就可以解决
        while (true){}

    }
}