Kafka connect cannot find broker in docker

Question

I have a docker-compose file to set up a Kafka infrastructure. The problem is, when I run the docker-compose for the first time on a machine then all the containers run fine, but when I STOP/REMOVE the containers and re-run the docker-compose then image container "cnfldemos/cp-server-connect-datagen:0.2.0-5.4.0" get an exit sometime. I just wanted to update that this problem is not constant and I cannot figure out the root cause.

Could you please help me with the above issue with image container "cnfldemos/cp-server-connect-datagen:0.2.0-5.4.0". By looking at the logs, I understand that there is an unknown host expectation but I don't know why it is trying to find 172.18.0.4 IP. It's not even my IP.

p.s. I am a novice at Kafka docker setup, please help!

Following are the error logs from the cnfldemos/cp-server-connect-datagen:0.2.0-5.4.0 container.

main] INFO org.apache.kafka.common.utils.AppInfoParser - Kafka version: 5.4.0-ccs
[main] INFO org.apache.kafka.common.utils.AppInfoParser - Kafka commitId: f4201a82bea68cc7
[main] INFO org.apache.kafka.common.utils.AppInfoParser - Kafka startTimeMs: 1585904457838
[kafka-admin-client-thread | adminclient-1] WARN org.apache.kafka.clients.NetworkClient - [AdminClient clientId=adminclient-1] Connection to node -1 (broker/172.18.0.4:29092) could not be established. Broker may not be available.
[kafka-admin-client-thread | adminclient-1] WARN org.apache.kafka.clients.NetworkClient - [AdminClient clientId=adminclient-1] Connection to node -1 (broker/172.18.0.4:29092) could not be established. Broker may not be available.
[kafka-admin-client-thread | adminclient-1] WARN org.apache.kafka.clients.NetworkClient - [AdminClient clientId=adminclient-1] Connection to node -1 (broker/172.18.0.4:29092) could not be established. Broker may not be available.
[kafka-admin-client-thread | adminclient-1] WARN org.apache.kafka.clients.NetworkClient - [AdminClient clientId=adminclient-1] Error connecting to node broker:29092 (id: -1 rack: null)
java.net.UnknownHostException: broker: Name or service not known
        at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)
        at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:929)
        at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1324)
        at java.net.InetAddress.getAllByName0(InetAddress.java:1277)
        at java.net.InetAddress.getAllByName(InetAddress.java:1193)
        at java.net.InetAddress.getAllByName(InetAddress.java:1127)
        at org.apache.kafka.clients.ClientUtils.resolve(ClientUtils.java:104)
        at org.apache.kafka.clients.ClusterConnectionStates$NodeConnectionState.currentAddress(ClusterConnectionStates.java:403)
        at org.apache.kafka.clients.ClusterConnectionStates$NodeConnectionState.access$200(ClusterConnectionStates.java:363)
        at org.apache.kafka.clients.ClusterConnectionStates.currentAddress(ClusterConnectionStates.java:151)
        at org.apache.kafka.clients.NetworkClient.initiateConnect(NetworkClient.java:955)
        at org.apache.kafka.clients.NetworkClient.ready(NetworkClient.java:289)
        at org.apache.kafka.clients.admin.KafkaAdminClient$AdminClientRunnable.sendEligibleCalls(KafkaAdminClient.java:969)
        at org.apache.kafka.clients.admin.KafkaAdminClient$AdminClientRunnable.run(KafkaAdminClient.java:1184)
        at java.lang.Thread.run(Thread.java:748)
[kafka-admin-client-thread | adminclient-1] WARN org.apache.kafka.clients.NetworkClient - [AdminClient clientId=adminclient-1] Error connecting to node broker:29092 (id: -1 rack: null)
java.net.UnknownHostException: broker

Following is the docker-compose.yml file.

I execute the the following docker-compose.yml file by using command

 docker-compose up -d  

version: '2.1'

services:

  zookeeper:
    image: confluentinc/cp-zookeeper:5.4.1
    hostname: zookeeper
    container_name: zookeeper
    ports:
      - "2181:2181"
    environment:
      ZOOKEEPER_CLIENT_PORT: 2181
      ZOOKEEPER_TICK_TIME: 2000


  broker:
    image: confluentinc/cp-server:5.4.1
    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'

  schema-registry:
    image: confluentinc/cp-schema-registry:5.4.1
    hostname: schema-registry
    container_name: schema-registry
    depends_on:
      - zookeeper
      - broker
    ports:
      - "8081:8081"
    environment:
      SCHEMA_REGISTRY_HOST_NAME: schema-registry
      SCHEMA_REGISTRY_KAFKASTORE_CONNECTION_URL: 'zookeeper:2181'

  rest-proxy:
    image: confluentinc/cp-kafka-rest:5.4.1
    depends_on:
      - zookeeper
      - broker
      - schema-registry
    ports:
      - 8082:8082
    hostname: rest-proxy
    container_name: rest-proxy
    environment:
      KAFKA_REST_HOST_NAME: rest-proxy
      KAFKA_REST_BOOTSTRAP_SERVERS: 'broker:29092'
      KAFKA_REST_LISTENERS: "http://0.0.0.0:8082"
      KAFKA_REST_SCHEMA_REGISTRY_URL: 'http://schema-registry:8081'

  kafka-topics-ui:
    image: landoop/kafka-topics-ui:0.9.4
    hostname: kafka-topics-ui
    ports:
      - "8000:8000"
    environment:
      KAFKA_REST_PROXY_URL: "http://rest-proxy:8082/"
      PROXY: "true"
    depends_on:
      - zookeeper
      - broker
      - schema-registry
      - rest-proxy

  connect:
    image: cnfldemos/cp-server-connect-datagen:0.2.0-5.4.0
    hostname: connect
    container_name: connect
    depends_on:
      - zookeeper
      - broker
      - schema-registry
    ports:
      - "8083:8083"
    environment:
      CONNECT_BOOTSTRAP_SERVERS: 'broker:29092'
      CONNECT_REST_ADVERTISED_HOST_NAME: connect
      CONNECT_REST_PORT: 8083
      CONNECT_GROUP_ID: compose-connect-group
      CONNECT_CONFIG_STORAGE_TOPIC: docker-connect-configs
      CONNECT_CONFIG_STORAGE_REPLICATION_FACTOR: 1
      CONNECT_OFFSET_FLUSH_INTERVAL_MS: 10000
      CONNECT_OFFSET_STORAGE_TOPIC: docker-connect-offsets
      CONNECT_OFFSET_STORAGE_REPLICATION_FACTOR: 1
      CONNECT_STATUS_STORAGE_TOPIC: docker-connect-status
      CONNECT_STATUS_STORAGE_REPLICATION_FACTOR: 1
      CONNECT_KEY_CONVERTER: org.apache.kafka.connect.storage.StringConverter
      CONNECT_VALUE_CONVERTER: io.confluent.connect.avro.AvroConverter
      CONNECT_VALUE_CONVERTER_SCHEMA_REGISTRY_URL: http://schema-registry:8081
      CONNECT_INTERNAL_KEY_CONVERTER: "org.apache.kafka.connect.json.JsonConverter"
      CONNECT_INTERNAL_VALUE_CONVERTER: "org.apache.kafka.connect.json.JsonConverter"
      CONNECT_ZOOKEEPER_CONNECT: 'zookeeper:2181'
      CLASSPATH: /usr/share/java/monitoring-interceptors/monitoring-interceptors-5.4.1.jar
      CONNECT_PRODUCER_INTERCEPTOR_CLASSES: "io.confluent.monitoring.clients.interceptor.MonitoringProducerInterceptor"
      CONNECT_CONSUMER_INTERCEPTOR_CLASSES: "io.confluent.monitoring.clients.interceptor.MonitoringConsumerInterceptor"
      CONNECT_PLUGIN_PATH: "/usr/share/java,/usr/share/confluent-hub-components"
      CONNECT_LOG4J_LOGGERS: org.apache.zookeeper=ERROR,org.I0Itec.zkclient=ERROR,org.reflections=ERROR

docker-compose ps

          Name                       Command            State                     Ports                   
----------------------------------------------------------------------------------------------------------
broker                      /etc/confluent/docker/run   Up      0.0.0.0:9092->9092/tcp                    
connect                     /etc/confluent/docker/run   Up      0.0.0.0:8083->8083/tcp, 9092/tcp          
topics-ui                   /run.sh                     Up      0.0.0.0:8000->8000/tcp                    
rest-proxy                  /etc/confluent/docker/run   Up      0.0.0.0:8082->8082/tcp                    
schema-registry             /etc/confluent/docker/run   Up      0.0.0.0:8081->8081/tcp                    
zookeeper                   /etc/confluent/docker/run   Up      0.0.0.0:2181->2181/tcp, 2888/tcp, 3888/tcp

docker-compose ps output after sometime

          Name                       Command             State                       Ports                   
-------------------------------------------------------------------------------------------------------------
broker                      /etc/confluent/docker/run   Up         0.0.0.0:9092->9092/tcp                    
connect                     /etc/confluent/docker/run   Exit 137                                             
topics-ui                   /run.sh                     Up         0.0.0.0:8000->8000/tcp                    
rest-proxy                  /etc/confluent/docker/run   Up         0.0.0.0:8082->8082/tcp                    
schema-registry             /etc/confluent/docker/run   Up         0.0.0.0:8081->8081/tcp                    
zookeeper                   /etc/confluent/docker/run   Up         0.0.0.0:2181->2181/tcp, 2888/tcp, 3888/tcp

we can notice that container 'connect' is exit 137 state.

Answer 1

I don't know why it is trying to find 172.18.0.4 IP. It's not even my IP.

That is your hypervisor IP.

---

Overall, seems like you might be running into a memory problem because you are connecting to the correct addresses (CONFLUENT_METRICS_REPORTER_BOOTSTRAP_SERVERS could be localhost:29092, actually), however the docker network is becoming unstable. (Run docker-compose rm -sf and docker system prune to get to a clean(er) state)

Solutions

1. Increase your Docker memory in the settings

2. Don't run containers you don't need (REST Proxy or Topics UI)