Why is http://localhost:9021/ not opening the Confluent Control Center?

Question

I am working on the Confluent Admin training and running labs in Docker for Desktop. PFA the docker-compose yaml file. The Confluent Control Center doesn't open in brower. I am using http://localhost:9021 to open. Ealier it used to open but not any more. The only change I have done in my computer is to install McAfee Live Safe. I even tried by turning off the Firewall, but it didn't help either.

Can someone please share if you had similar experience and how you overcame this issue?

docker-compose.yaml file.

    version: "3.5"
    services:
      zk-1:
        image: confluentinc/cp-zookeeper:5.3.1
        hostname: zk-1
        container_name: zk-1
        ports:
          - "12181:2181"
        volumes:
          - data-zk-log-1:/var/lib/zookeeper/log
          - data-zk-data-1:/var/lib/zookeeper/data
        networks:
          - confluent
        environment:
          - ZOOKEEPER_SERVER_ID=1
          - ZOOKEEPER_CLIENT_PORT=2181
          - ZOOKEEPER_TICK_TIME=2000
          - ZOOKEEPER_INIT_LIMIT=5
          - ZOOKEEPER_SYNC_LIMIT=2
          - ZOOKEEPER_SERVERS=zk-1:2888:3888;zk-2:2888:3888;zk-3:2888:3888
      
      zk-2:
        image: confluentinc/cp-zookeeper:5.3.1
        hostname: zk-2
        container_name: zk-2
        ports:
          - "22181:2181"
        volumes:
          - data-zk-log-2:/var/lib/zookeeper/log
          - data-zk-data-2:/var/lib/zookeeper/data
        networks:
          - confluent
        environment:
          - ZOOKEEPER_SERVER_ID=2
          - ZOOKEEPER_CLIENT_PORT=2181
          - ZOOKEEPER_TICK_TIME=2000
          - ZOOKEEPER_INIT_LIMIT=5
          - ZOOKEEPER_SYNC_LIMIT=2
          - ZOOKEEPER_SERVERS=zk-1:2888:3888;zk-2:2888:3888;zk-3:2888:3888
      
      zk-3:
        image: confluentinc/cp-zookeeper:5.3.1
        hostname: zk-3
        container_name: zk-3
        ports:
          - "32181:2181"
        volumes:
          - data-zk-log-3:/var/lib/zookeeper/log
          - data-zk-data-3:/var/lib/zookeeper/data
        networks:
          - confluent
        environment:
          - ZOOKEEPER_SERVER_ID=3
          - ZOOKEEPER_CLIENT_PORT=2181
          - ZOOKEEPER_TICK_TIME=2000
          - ZOOKEEPER_INIT_LIMIT=5
          - ZOOKEEPER_SYNC_LIMIT=2
          - ZOOKEEPER_SERVERS=zk-1:2888:3888;zk-2:2888:3888;zk-3:2888:3888
    
      kafka-1:
        image: confluentinc/cp-enterprise-kafka:5.3.1
        hostname: kafka-1
        container_name: kafka-1
        ports:
          - "19092:9092"
        networks:
          - confluent
        volumes:
          - data-kafka-1:/var/lib/kafka/data
        environment:
          KAFKA_BROKER_ID: 101
          KAFKA_ZOOKEEPER_CONNECT: zk-1:2181,zk-2:2181,zk-3:2181
          KAFKA_LISTENERS: DOCKER://kafka-1:9092,HOST://kafka-1:19092
          KAFKA_ADVERTISED_LISTENERS: DOCKER://kafka-1:9092,HOST://localhost:19092
          KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: DOCKER:PLAINTEXT,HOST:PLAINTEXT
          KAFKA_INTER_BROKER_LISTENER_NAME: DOCKER
          KAFKA_METRIC_REPORTERS: "io.confluent.metrics.reporter.ConfluentMetricsReporter"
          CONFLUENT_METRICS_REPORTER_BOOTSTRAP_SERVERS: "kafka-1:9092,kafka-2:9092,kafka-3:9092"
    
      kafka-2:
        image: confluentinc/cp-enterprise-kafka:5.3.1
        hostname: kafka-2
        container_name: kafka-2
        ports:
          - "29092:9092"
        networks:
          - confluent
        volumes:
          - data-kafka-2:/var/lib/kafka/data
        environment:
          KAFKA_BROKER_ID: 102
          KAFKA_ZOOKEEPER_CONNECT: zk-1:2181,zk-2:2181,zk-3:2181
          KAFKA_LISTENERS: DOCKER://kafka-2:9092,HOST://kafka-2:29092
          KAFKA_ADVERTISED_LISTENERS: DOCKER://kafka-2:9092,HOST://localhost:29092
          KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: DOCKER:PLAINTEXT,HOST:PLAINTEXT
          KAFKA_INTER_BROKER_LISTENER_NAME: DOCKER
          KAFKA_METRIC_REPORTERS: "io.confluent.metrics.reporter.ConfluentMetricsReporter"
          CONFLUENT_METRICS_REPORTER_BOOTSTRAP_SERVERS: "kafka-1:9092,kafka-2:9092,kafka-3:9092"
    
      kafka-3:
        image: confluentinc/cp-enterprise-kafka:5.3.1
        hostname: kafka-3
        container_name: kafka-3
        ports:
          - "39092:9092"
        networks:
          - confluent
        volumes:
          - data-kafka-3:/var/lib/kafka/data
        environment:
          KAFKA_BROKER_ID: 103
          KAFKA_ZOOKEEPER_CONNECT: zk-1:2181,zk-2:2181,zk-3:2181
          KAFKA_LISTENERS: DOCKER://kafka-3:9092,HOST://kafka-3:39092
          KAFKA_ADVERTISED_LISTENERS: DOCKER://kafka-3:9092,HOST://localhost:39092
          KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: DOCKER:PLAINTEXT,HOST:PLAINTEXT
          KAFKA_INTER_BROKER_LISTENER_NAME: DOCKER
          KAFKA_METRIC_REPORTERS: "io.confluent.metrics.reporter.ConfluentMetricsReporter"
          CONFLUENT_METRICS_REPORTER_BOOTSTRAP_SERVERS: "kafka-1:9092,kafka-2:9092,kafka-3:9092"
    
      schema-registry:
        image: confluentinc/cp-schema-registry:5.3.1
        hostname: schema-registry
        container_name: schema-registry
        ports:
          - "8081:8081"
        networks:
          - confluent
        environment:
          SCHEMA_REGISTRY_HOST_NAME: schema-registry
          SCHEMA_REGISTRY_KAFKASTORE_BOOTSTRAP_SERVERS: "kafka-1:9092,kafka-2:9092,kafka-3:9092"
          SCHEMA_REGISTRY_LISTENERS: "http://schema-registry:8081,http://localhost:8081"
          # Uses incorrect container utility belt (CUB) environment variables due to bug.
          # See https://github.com/confluentinc/cp-docker-images/issues/807. A fix was merged that
          # will be available in the CP 5.4 image.
          KAFKA_REST_CUB_KAFKA_TIMEOUT: 120
          KAFKA_REST_CUB_KAFKA_MIN_BROKERS: 3
    
      connect:
        image: confluentinc/cp-kafka-connect:5.3.1
        hostname: connect
        container_name: connect
        ports:
          - "8083:8083"
        volumes:
          - ./data:/data
        networks:
          - confluent
        environment:
          CONNECT_PRODUCER_INTERCEPTOR_CLASSES: io.confluent.monitoring.clients.interceptor.MonitoringProducerInterceptor
          CONNECT_CONSUMER_INTERCEPTOR_CLASSES: io.confluent.monitoring.clients.interceptor.MonitoringConsumerInterceptor
          CONNECT_BOOTSTRAP_SERVERS: kafka-1:9092,kafka-2:9092,kafka-3:9092
          CONNECT_GROUP_ID: "connect"
          CONNECT_CONFIG_STORAGE_TOPIC: "connect-config"
          CONNECT_OFFSET_STORAGE_TOPIC: "connect-offsets"
          CONNECT_STATUS_STORAGE_TOPIC: "connect-status"
          CONNECT_KEY_CONVERTER: "io.confluent.connect.avro.AvroConverter"
          CONNECT_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"
          CONNECT_INTERNAL_KEY_CONVERTER: org.apache.kafka.connect.json.JsonConverter
          CONNECT_INTERNAL_VALUE_CONVERTER: org.apache.kafka.connect.json.JsonConverter
          CONNECT_REST_ADVERTISED_HOST_NAME: "connect"
          CONNECT_LOG4J_ROOT_LOGLEVEL: INFO
          CONNECT_LOG4J_LOGGERS: org.reflections=ERROR
          CONNECT_PLUGIN_PATH: /usr/share/java
          CONNECT_REST_HOST_NAME: "connect"
          CONNECT_REST_PORT: 8083
          CONNECT_CUB_KAFKA_TIMEOUT: 120
    
      ksql-server:
        image: confluentinc/cp-ksql-server:5.3.1
        hostname: ksql-server
        container_name: ksql-server
        ports:
          - "8088:8088"
        networks:
          - confluent
        environment:
          KSQL_CONFIG_DIR: "/etc/ksql"
          KSQL_LOG4J_OPTS: "-Dlog4j.configuration=file:/etc/ksql/log4j-rolling.properties"
          KSQL_BOOTSTRAP_SERVERS: kafka-1:9092,kafka-2:9092,kafka-3:9092
          KSQL_HOST_NAME: ksql-server
          KSQL_APPLICATION_ID: "etl-demo"
          KSQL_LISTENERS: "http://0.0.0.0:8088"
          # Set the buffer cache to 0 so that the KSQL CLI shows all updates to KTables for learning purposes.
          # The default is 10 MB, which means records in a KTable are compacted before showing output.
          # Change cache.max.bytes.buffering and commit.interval.ms to tune this behavior.
          KSQL_CACHE_MAX_BYTES_BUFFERING: 0
          KSQL_KSQL_SCHEMA_REGISTRY_URL: "http://schema-registry:8081"
          KSQL_PRODUCER_INTERCEPTOR_CLASSES: "io.confluent.monitoring.clients.interceptor.MonitoringProducerInterceptor"
          KSQL_CONSUMER_INTERCEPTOR_CLASSES: "io.confluent.monitoring.clients.interceptor.MonitoringConsumerInterceptor"
    
      control-center:
        image: confluentinc/cp-enterprise-control-center:5.3.1
        hostname: control-center
        container_name: control-center
        restart: always
        networks:
          - confluent
        ports:
          - "9021:9021"
        environment:
          CONTROL_CENTER_BOOTSTRAP_SERVERS: kafka-1:9092,kafka-2:9092,kafka-3:9092
          CONTROL_CENTER_ZOOKEEPER_CONNECT: zk-1:2181,zk-2:2181,zk-3:2181
          CONTROL_CENTER_STREAMS_NUM_STREAM_THREADS: 4
          CONTROL_CENTER_REPLICATION_FACTOR: 3
          CONTROL_CENTER_CONNECT_CLUSTER: "connect:8083"
          CONTROL_CENTER_KSQL_URL: "http://ksql-server:8088"
          CONTROL_CENTER_KSQL_ADVERTISED_URL: "http://localhost:8088"
          CONTROL_CENTER_SCHEMA_REGISTRY_URL: "http://schema-registry:8081"
    
      tools:
        image: cnfltraining/training-tools:5.3
        hostname: tools
        container_name: tools
        volumes:
          - ${PWD}/:/apps
        working_dir: /apps
        networks:
          - confluent
        command: /bin/bash
        tty: true
    
    volumes:
      data-zk-log-1:
      data-zk-data-1:
      data-zk-log-2:
      data-zk-data-2:
      data-zk-log-3:
      data-zk-data-3:
      data-kafka-1:
      data-kafka-2:
      data-kafka-3:
    
    networks:
      confluent:

All the docker containers are up and running; all respective confluent services are up.

Thanks !!

Answer 1

Finally...I got an answer to this from Confluent Support.

The version of control center in the labs expires after 30 days.

This can reset by removing all the containers and volumes on the PC.

1. docker-compose down -v will exit and remove all the containers and volumes.
2. Re-run the docker-compose up -d command.

Now give a minute or two before opening the Control Center in any browser. PS Docker should have been given at least 6GB of memory to run all the containers.

Thanks.