KafkaException: No key found on line 1 at kafka.tools.ConsoleProducer$LineMessageReader.readMessage

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In few words, I started Kafka, created succesfully a topic, started a producer with key enabled. So far so good. I send a simple message and I get

root@kafka:/# kafka-console-producer --broker-list localhost:9092 --topic testkey --property "parse.key=true" propert
y "key.separator=:"
>1:fisrtmessage
org.apache.kafka.common.KafkaException: No key found on line 1: 1:fisrtmessage
        at kafka.tools.ConsoleProducer$LineMessageReader.readMessage(ConsoleProducer.scala:275)
        at kafka.tools.ConsoleProducer$.main(ConsoleProducer.scala:55)
        at kafka.tools.ConsoleProducer.main(ConsoleProducer.scala)
root@kafka:/#

Here is both produccer and consumer. As you can see, the consumer didn't receive the messsage and the producer crached.

cmd screens

docker-compose.yml

version: '3'

services:
  zookeeper:
    image: confluentinc/cp-zookeeper:5.4.0
    hostname: zookeeper
    container_name: zookeeper
    ports:
      - "2181:2181"
    environment:
      ZOOKEEPER_CLIENT_PORT: 2181
      ZOOKEEPER_TICK_TIME: 2000

  broker:
    image: confluentinc/cp-server:5.4.0
    hostname: broker
    container_name: broker
    depends_on:
      - zookeeper
    ports:
      - "9092:9092"
    environment:
      KAFKA_BROKER_ID: 1
      KAFKA_ZOOKEEPER_CONNECT: 'zookeeper:2181'
      KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,PLAINTEXT_HOST:PLAINTEXT
      KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://broker:29092,PLAINTEXT_HOST://localhost:9092
      KAFKA_METRIC_REPORTERS: io.confluent.metrics.reporter.ConfluentMetricsReporter
      KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
      KAFKA_GROUP_INITIAL_REBALANCE_DELAY_MS: 0
      KAFKA_CONFLUENT_LICENSE_TOPIC_REPLICATION_FACTOR: 1
      CONFLUENT_METRICS_REPORTER_BOOTSTRAP_SERVERS: broker:29092
      CONFLUENT_METRICS_REPORTER_ZOOKEEPER_CONNECT: zookeeper:2181
      CONFLUENT_METRICS_REPORTER_TOPIC_REPLICAS: 1
      CONFLUENT_METRICS_ENABLE: 'true'
      CONFLUENT_SUPPORT_CUSTOMER_ID: 'anonymous'

  kafka-tools:
    image: confluentinc/cp-kafka:5.4.0
    hostname: kafka
    container_name: kafka
    command: ["tail", "-f", "/dev/null"]
    network_mode: "host"
kafka-producer-api confluent-platform apache-kafka docker apache-zookeeper
1 Answers

Your call of the kafka-console-producer is missing -- in the second call of property.

This means that the keySeparator is not the one that you have provided (:) but it rather falls back to the default value. According to the code of the ConsoleProducer the default value is:

var keySeparator = "\t"

As your provided string does not contain any tabs it will throw the Exception "No key found on line ..." which is done at this line of the code.

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