生产者端的同步发送和异步发送
生产者的同步发送
如果⽣产者发送消息没有收到ack，⽣产者会阻塞，阻塞到3s的时间，如果还没有收到消息，会进⾏重试。重试的次数3次。
RecordMetadata metadata = producer.send(producerRecord).get();
System.out.println("同步⽅式发送消息结果：" + "topic-" +
metadata.topic() + "|partition-" + metadata.partition() + "|offset-" + metadata.offset());
生产者的异步发送消息
异步发送，⽣产者发送完消息后就可以执⾏之后的业务，broker在收到消息后异步调⽤⽣产者提供的callback回调⽅法。
//5.异步发送消息
producer.send(producerRecord, new Callback() {
public void onCompletion(RecordMetadata metadata, Exception exception) {
if (exception != null) {
System.err.println("发送消息失败：" +
exception.getStackTrace());
}
if (metadata != null) {
System.out.println("异步⽅式发送消息结果：" + "topic-" +
metadata.topic() + "|partition-" + metadata.partition() + "|offset-" + metadata.offset());
}
}
});
测试
package com.example.kafka;
import org.apache.kafka.clients.producer.*;
import org.apache.kafka.common.serialization.StringSerializer;
import java.util.Properties;
import java.util.concurrent.ExecutionException;
public class MySimpleProducer {
private final static String TOPIC_NAME = "test";
public static void main(String[] args) throws ExecutionException,
InterruptedException {
//1.设置参数
Properties props = new Properties();
props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "81.68.232.188:9092,81.68.232.188:9093,81.68.232.188:9094");
//把发送的key从字符串序列化为字节数组
props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG,
StringSerializer.class.getName());
//把发送消息value从字符串序列化为字节数组
props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG,
StringSerializer.class.getName());
//2.创建⽣产消息的客户端，传⼊参数
Producer<String, String> producer = new KafkaProducer<>(props);
//3.创建消息
//key：作⽤是决定了往哪个分区上发，value：具体要发送的消息内容
ProducerRecord<String, String> producerRecord = new ProducerRecord<>
(TOPIC_NAME,1, "key1", "hello, kafka");
//4.发送消息,得到消息发送的元数据并输出
// RecordMetadata metadata = producer.send(producerRecord).get();
// System.out.println("同步⽅式发送消息结果：" + "topic-" +
// metadata.topic() + "|partition-" + metadata.partition()
// + "|offset-" + metadata.offset());
//5.异步发送消息
producer.send(producerRecord, new Callback() {
public void onCompletion(RecordMetadata metadata, Exception exception) {
if (exception != null) {
System.err.println("发送消息失败：" +
exception.getStackTrace());
}
if (metadata != null) {
System.out.println("异步⽅式发送消息结果：" + "topic-" +
metadata.topic() + "|partition-" + metadata.partition() + "|offset-" + metadata.offset());
}
}
});
Thread.sleep(100000);
}
}
注意
总结
异步发送会存在数据丢失的问题，同步发送更为常用