一、背景

明天尝试应用 kafka 的 生产者 api 写一下，音讯发送，后果遇到以下问题，
Topic xxx not present in metadata after 60000 ms，找了半天后果发现是jar包引入不全导致的，为防当前遗记，在此记录一下。

二、场景还原

1、jar包引入

<dependency>    <groupId>org.apache.kafka</groupId>    <artifactId>kafka-clients</artifactId>    <version>2.6.0</version></dependency>

2、jar代码

public class KafkaProducerDemo {    public static void main(String[] args) {        Properties properties = new Properties();        properties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "127.0.0.1:9092,127.0.0.1:9093,127.0.0.1:9094");        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");        properties.put(ProducerConfig.ACKS_CONFIG, "all");        properties.put(ProducerConfig.BUFFER_MEMORY_CONFIG, 33554432);        properties.put(ProducerConfig.RETRIES_CONFIG, 0);        properties.put(ProducerConfig.RETRY_BACKOFF_MS_CONFIG, 300);        properties.put(ProducerConfig.BATCH_SIZE_CONFIG, 16384);        // KafkaProducer 是线程平安的，能够多个线程应用用一个 KafkaProducer        KafkaProducer<String, String> kafkaProducer = new KafkaProducer<>(properties);        for (int i = 0; i < 100; i++) {            ProducerRecord<String, String> record = new ProducerRecord<>("topic-a", "value - (" + i + 1 + ")");            kafkaProducer.send(record, new Callback() {                @Override                public void onCompletion(RecordMetadata metadata, Exception exception) {                    if (exception != null) {                        System.err.println("发送数据到kafka中,产生了异样.");                        exception.printStackTrace();                        return;                    }                    System.out.println("topic: " + metadata.topic() + " offset: " + metadata.offset() + " partition: "                            + metadata.partition());                }            });        }        System.out.println("音讯发送实现");        kafkaProducer.close();    }}

3、运行后果


运行下面的代码呈现了 org.apache.kafka.common.errors.TimeoutException: Topic topic-a not present in metadata after 60000 ms 异样。

三、问题解决

其实这个问题很简略，在启动我的项目的时候退出 logback.xml 配置文件，而后退出logback相干的jar包，发现，短少jackson的jar，引入之后就好了。

<dependency>    <groupId>org.apache.kafka</groupId>    <artifactId>kafka-clients</artifactId>    <version>2.6.0</version></dependency><dependency>    <groupId>com.fasterxml.jackson.core</groupId>    <artifactId>jackson-databind</artifactId>    <version>2.12.0</version></dependency>

四、参考文档

1、https://stackoverflow.com/questions/63714401/org-apache-kafka-common-errors-timeoutexception-topic-not-present-in-metadata-a

2、http://kafka.apache.org/26/documentation.html#producerapi