Cannot produce Message when Main Thread sleep less than 1000

问题

When I am using the Java API of Kafka,if I let my main Thread sleep less than 2000ns,it cannot prodece any message.I really want to know why this happen?

Here is my producer:

public class Producer {
    private final KafkaProducer<String, String> producer;
    private final String topic;

    public Producer(String topic, String[] args) {
        //......
        //......
        producer = new KafkaProducer<>(props);
        this.topic = topic;
    }

    public void producerMsg() throws InterruptedException {
        String data = "Apache Storm is a free and open source distributed";
        data = data.replaceAll("[\\pP‘’“”]", "");
        String[] words = data.split(" ");
        Random _rand = new Random();

        Random rnd = new Random();
        int events = 10;
        for (long nEvents = 0; nEvents < events; nEvents++) {
            long runtime = new Date().getTime();
            int lastIPnum = rnd.nextInt(255);
            String ip = "192.168.2." + lastIPnum;
            String msg = words[_rand.nextInt(words.length)];
            try {
                producer.send(new ProducerRecord<>(topic, ip, msg));
                System.out.println("Sent message: (" + ip + ", " + msg + ")");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Producer producer = new Producer(Constants.TOPIC, args);
        producer.producerMsg();
        //If I write Thread.sleep(1000),It will not work!!!!!!!!!!!!!!!!!!!!
        Thread.sleep(2000);
    }
}

appreciate that

回答1:

can you show the props you are using for configuring the Producer ? I'm only guessing that it's possible that ...

In the producerMsg() you are using the async way to use the producer so just producer.send() which means that the message is put in an internal buffer for making batches that will be sent later. The producer has an internal thread to get from the buffer and sending the batch. Maybe that only 1000 ms aren't enough for reaching the condition where the producer really sends messages (see batch.size and linger.ms), the main application ends and the producer dies without sending messages. Giving it more time (2000 ms), it works. Btw, I didn't try the code.

So the reason seems to be your :

props.put("linger.ms", 1000);

that matches with your sleep. So the producer will start to send messages after 1000 ms, because the batch isn't already full (batch.size is 16 MB). At same time, the main thread ends after sleeping 1 secs and the producer doesn't send messages. You have to use a lower linger.ms time.

来源：https://stackoverflow.com/questions/44802818/cannot-produce-message-when-main-thread-sleep-less-than-1000