Spring 应用程序在同一个集群内运行时无法连接到 Kafka，但在从集群外运行时可以工作

Question

Spring application is working fine when it runs locally on my machine and accesses Kafka through docker, but it doesn't work when I add my Spring Application as a container inside of the cluster. I get error message: "Connection to node -1 (localhost/127.0.0.1:9092) could not be established. Broker may not be available"

Listed below is the docker-compose, dockerfile, and application.properties of the spring application.

docker-compose.yml

version: "3"

services:
  zookeeper:
    image: 'bitnami/zookeeper:latest'
    ports:
      - '2181:2181'
    environment:
      - ALLOW_ANONYMOUS_LOGIN=yes
  kafka:
    image: 'bitnami/kafka:latest'
    ports:
      - '9092:9092'
    environment:
      - KAFKA_BROKER_ID=1
      - KAFKA_LISTENERS=PLAINTEXT://:9092
      - KAFKA_ADVERTISED_LISTENERS=PLAINTEXT://127.0.0.1:9092
      - KAFKA_ZOOKEEPER_CONNECT=zookeeper:2181
      - ALLOW_PLAINTEXT_LISTENER=yes
    depends_on:
      - zookeeper
  app:
    image: 'someuser/imagename'
    ports:
      - '8080:8080'
    depends_on:
      - kafka

applications.properties

server.port = 8080
spring.kafka.consumer.bootstrap.servers=localhost:9092
spring.kafka.consumer.group-id=mygroup 
spring.kafka.consumer.auto-offset-reset=earliest
spring.kafka.consumer.key-deserializer=org.apache.kafka.common.serialization.StringDeserializer
spring.kafka.consume.value-deserializer=org.apache.kafka.common.serialization.StringDeserializer

spring.kafka.producer.bootstrap-servers=localhost:9092
spring.kafka.producer.key-deserializer=org.apache.kafka.common.serialization.StringDeserializer
spring.kafka.producer.value-deserialzier=org.apache.kafka.common.serialization.StringDeserializer

Dockerfile

FROM openjdk:17

WORKDIR /app

EXPOSE 8080
EXPOSE 9092

COPY .mvn/ .mvn
COPY mvnw pom.xml ./
RUN ./mvnw dependency:go-offline

COPY src ./src

CMD ["./mvnw", "spring-boot:run"]

Answer 1

With spring.kafka.producer.bootstrap-servers=localhost:9092 and spring.kafka.consumer.bootstrap.servers=localhost:9092 your application is technically calling it's own container on port 9092 and not the one that kafka is deployed on.

If you change localhost:9092 to kafka:9092 it should work ( https://docs.docker.com/compose/networking/ ). (locally it wont, but it should connect when deployed through docker)

Try setting a different application profile for local and docker deployments.