Repro for xk6-kafka issue https://github.com/mostafa/xk6-kafka/issues/148

burstMessages.js

import {
  Writer,
  Connection,
  AVRO_SERIALIZER,
  STRING_SERIALIZER,
} from "k6/x/kafka";

const brokers = ["kafka:29092"];

const writer = new Writer({
  brokers: brokers,
  topic: "mytopic",
  autoCreateTopic: false,
});

const connection = new Connection({
  address: brokers[0],
});

const config = {
  producer: {
    keySerializer: STRING_SERIALIZER,
    valueSerializer: AVRO_SERIALIZER,
  },
  schemaRegistry: {
    url: "http://schemaregistry:8085",
  },
};

export const options = {
  vus: 10,
  duration: "1m",
};

export default function () {
  for (let i = 0; i < 5; i++) {
    let sentMessages = [
      {
        key: "someKey",
        value: JSON.stringify({
          someField: `value-${__VU}-${__ITER}-${i}`,
        }),
      },
    ];

    writer.produce({
      messages: sentMessages,
      config: config,
    });
  }
}

export function teardown(data) {
  writer.close();
  connection.close();
}

docker-compose.yml

---
version: "3"

networks:
  mynetwork:
    driver: bridge
    name: mynetwork

services:
  zookeeper:
    image: zookeeper:3.7.0
    hostname: zookeeper
    ports:
      - 2181:2181
    networks:
      - mynetwork

  kafka:
    image: wurstmeister/kafka:2.13-2.8.1
    ports:
      - 9092:9092
    depends_on:
      - zookeeper
    environment:
      - KAFKA_BROKER_ID=1
      - KAFKA_CREATE_TOPICS=mytopic:1:1
      - KAFKA_ZOOKEEPER_CONNECT=zookeeper:2181
      - KAFKA_LISTENERS=PLAINTEXT://:29092,EXTERNAL://0.0.0.0:9092
      - KAFKA_ADVERTISED_LISTENERS=PLAINTEXT://kafka:29092,EXTERNAL://localhost:9092
      - KAFKA_LISTENER_SECURITY_PROTOCOL_MAP=PLAINTEXT:PLAINTEXT,EXTERNAL:PLAINTEXT
      - KAFKA_INTER_BROKER_LISTENER_NAME=PLAINTEXT
      - KAFKA_SCHEMA_REGISTRY_URL=schemaregistry:8085
    networks:
      - mynetwork

  kafka-ui:
    image: provectuslabs/kafka-ui:latest
    ports:
      - 8080:8080
    depends_on:
      - zookeeper
      - kafka
      - schemaregistry
    environment:
      KAFKA_CLUSTERS_0_NAME: local
      KAFKA_CLUSTERS_0_BOOTSTRAPSERVERS: kafka:29092
      KAFKA_CLUSTERS_0_ZOOKEEPER: zookeeper:2181
      KAFKA_CLUSTERS_0_SCHEMAREGISTRY: http://schemaregistry:8085
    networks:
      - mynetwork

  schemaregistry:
    image: confluentinc/cp-schema-registry:latest
    ports:
      - 8085:8085
    depends_on:
      - zookeeper
      - kafka
    environment:
      SCHEMA_REGISTRY_KAFKASTORE_BOOTSTRAP_SERVERS: PLAINTEXT://kafka:29092
      SCHEMA_REGISTRY_KAFKASTORE_CONNECTION_URL: zookeeper:2181
      SCHEMA_REGISTRY_KAFKASTORE_SECURITY_PROTOCOL: PLAINTEXT
      SCHEMA_REGISTRY_HOST_NAME: schemaregistry
      SCHEMA_REGISTRY_LISTENERS: http://schemaregistry:8085
      SCHEMA_REGISTRY_SCHEMA_REGISTRY_INTER_INSTANCE_PROTOCOL: "http"
    networks:
      - mynetwork

myschema.json

{
  "schema": "{\"type\":\"record\",\"name\":\"MySchema\",\"fields\":[{\"name\":\"someField\",\"type\":\"string\"}]}"
}