Kafka: Resolving Error: Opening socket connection to server localhost/127.0.0.1:2181. Will not attempt to authenticate using SASL (unknown error)?

Question

On the startup of kafka schema registry or kafka server I am facing below error and the servers startup is failing. Could someone help me resolve the below error.

SendThread(localhost:2181)] INFO org.apache.zookeeper.ClientCnxn - Opening socket connection to server localhost/127.0.0.1:2181. Will not attempt to authenticate using SASL (unknown error)

[main-SendThread(localhost:2181)] INFO org.apache.zookeeper.ClientCnxn - Socket error occurred: localhost/127.0.0.1:2181: Connection refused

[main-SendThread(localhost:2181)] INFO org.apache.zookeeper.ClientCnxn - Opening socket connection to server localhost/127.0.0.1:2181. Will not attempt to authenticate using SASL (unknown error)

[main-SendThread(localhost:2181)] INFO org.apache.zookeeper.ClientCnxn - Socket error occurred: localhost/127.0.0.1:2181: Connection refused

[main-SendThread(localhost:2181)] INFO org.apache.zookeeper.ClientCnxn - Opening socket connection to server localhost/127.0.0.1:2181. Will not attempt to authenticate using SASL (unknown error)

My Docker Compose file is as below -

version: "3.7"
services:
  postgres:
    image: debezium/postgres:13
    ports:
      - 5432:5432
    environment:
      - POSTGRES_USER=docker
      - POSTGRES_PASSWORD=docker
      - POSTGRES_DB=exampledb

  zookeeper:
    image: confluentinc/cp-zookeeper:5.5.3
    environment:
      ZOOKEEPER_CLIENT_PORT: 2181
    ports:
      - 2181:2181

  kafka:
    image: confluentinc/cp-enterprise-kafka:5.5.3
    depends_on: [zookeeper]
    environment:
      KAFKA_ZOOKEEPER_CONNECT: "localhost:2181"
      KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka:9092
      KAFKA_BROKER_ID: 1
      KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
      KAFKA_JMX_PORT: 9991
    ports:
      - 9092:9092

  debezium:
    image: debezium/connect:1.4
    environment:
      BOOTSTRAP_SERVERS: kafka:9092
      GROUP_ID: 1
      CONFIG_STORAGE_TOPIC: connect_configs
      OFFSET_STORAGE_TOPIC: connect_offsets
      KEY_CONVERTER: io.confluent.connect.avro.AvroConverter
      VALUE_CONVERTER: io.confluent.connect.avro.AvroConverter
      CONNECT_KEY_CONVERTER_SCHEMA_REGISTRY_URL: http://schema-registry:8081
      CONNECT_VALUE_CONVERTER_SCHEMA_REGISTRY_URL: http://schema-registry:8081
    depends_on: [kafka]
    ports:
      - 8083:8083

  schema-registry:
    image: confluentinc/cp-schema-registry:5.5.3
    environment:
      - SCHEMA_REGISTRY_KAFKASTORE_CONNECTION_URL=localhost:2181
      - SCHEMA_REGISTRY_HOST_NAME=schema-registry
      - SCHEMA_REGISTRY_LISTENERS=http://schema-registry:8081,http://localhost:8081
    ports:
      - 8081:8081
    depends_on: [zookeeper, kafka]

Answer 1

KAFKA_ZOOKEEPER_CONNECT needs to point at the Zookeeper service, not the Kafka container's localhost .

I suggest you start with Confluent's Docker getting started guide which has working Compose files, or Debezium documentation as well.