英文:
How kafka producer works in asynchronous mode
问题
以下是您提供的代码的翻译部分：
我有一个简单的代码来发送消息
private static void send(KafkaProducer<String, String> producer) {System.out.println(Thread.currentThread() + " before");producer.send(new ProducerRecord<String, String>("test", "test"), (metadata, exception) -> {if (exception == null) {System.out.println(metadata.partition());} else {exception.printStackTrace();}});System.out.println(Thread.currentThread() + " after");}
和Kafka配置
Properties properties = new Properties();properties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9091");properties.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");properties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");KafkaProducer<String, String> producer = new KafkaProducer<>(properties);
我的Kafka已经关闭。
我期望如果我调用send两次
send(producer);send(producer);
, 我将连续获得两条“Thread before”的记录，因为我们在异步模式下工作
Thread beforeThread before
但我只在第一条记录出现错误后才看到第二条记录的处理开始
Thread[main,5,main] beforeorg.apache.kafka.common.errors.TimeoutException: Topic test not present in metadata after 60000 ms.Thread[main,5,main] afterThread[main,5,main] before
我认为我误解了Kafka的异步模式。
英文:
I have a simple code to send a message
private static void send(KafkaProducer<String, String> producer) {System.out.println(Thread.currentThread()+" before");producer.send(new ProducerRecord<String, String>("test", "test"), (metadata, exception) -> {if (exception == null) {System.out.println(metadata.partition());} else {exception.printStackTrace();}});System.out.println(Thread.currentThread()+" after");}
And kafka config
Properties properties = new Properties();properties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9091");properties.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");properties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");KafkaProducer<String, String> producer = new KafkaProducer<>(properties);
My kafka is shutdown.
I expected if I call send twice
send(producer);send(producer);
, I will get two Thread before records one after the other since we are working in asynchronous mode
Thread beforeThread before
But I see the start of processing the second record only after the error of the first
Thread[main,5,main] beforeorg.apache.kafka.common.errors.TimeoutException: Topic test not present in metadata after 60000 ms.Thread[main,5,main] afterThread[main,5,main] before
I think I misunderstood kafka's asynchronous mode
答案1
得分: 1
第一个发送请求是阻塞的，用于创建主题。
另外，你的 after 应该在 lambda 回调体内。
英文:
The first send request is blocking to create the topic.
Also, your after should be within the lamdba callback body.
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