<p>The repo used is: <a href="https://github.com/Yolean/kubernetes-kafka/" rel="nofollow noreferrer">https://github.com/Yolean/kubernetes-kafka/</a></p>

<p>So I'm trying to run a Kafka cluster that connects to a Zookeeper cluster in Kubernetes, the first pod runs alright, but then the second Kafka pod tries to connect to the zookeeper cluster and it has this error:</p>

<blockquote>
  <p>kafka.common.InconsistentBrokerIdException: Configured broker.id 1
  doesn't match stored broker.id 0 in meta.properties. If you moved your
  data, make sure your configured broker.id matches. If you intend to
  create a new broker, you should remove all data in your data
  directories (log.dirs).</p>
</blockquote>

<p>I understand the error is in the second broker id but shouldn't the zookeeper cluster allow multiple broker connections? or how could the config be changed to allow it?</p>

<p>or is it a Kafka configuration problem? The config file is:</p>

<pre><code>kind: ConfigMap
metadata:
  name: broker-config
  namespace: whitenfv
  labels:
    name: kafka
    system: whitenfv
apiVersion: v1
data:
  init.sh: |-
    #!/bin/bash
    set -x
    cp /etc/kafka-configmap/log4j.properties /etc/kafka/

    KAFKA_BROKER_ID=${HOSTNAME##*-}
    SEDS=("s/#init#broker.id=#init#/broker.id=$KAFKA_BROKER_ID/")
    LABELS="kafka-broker-id=$KAFKA_BROKER_ID"
    ANNOTATIONS=""

    hash kubectl 2&gt;/dev/null || {
      SEDS+=("s/#init#broker.rack=#init#/#init#broker.rack=# kubectl not found in path/")
    } &amp;&amp; {
      ZONE=$(kubectl get node "$NODE_NAME" -o=go-template='{{index .metadata.labels "failure-domain.beta.kubernetes.io/zone"}}')
      if [ $? -ne 0 ]; then
        SEDS+=("s/#init#broker.rack=#init#/#init#broker.rack=# zone lookup failed, see -c init-config logs/")
      elif [ "x$ZONE" == "x&lt;no value&gt;" ]; then
        SEDS+=("s/#init#broker.rack=#init#/#init#broker.rack=# zone label not found for node $NODE_NAME/")
      else
        SEDS+=("s/#init#broker.rack=#init#/broker.rack=$ZONE/")
        LABELS="$LABELS kafka-broker-rack=$ZONE"
      fi

      OUTSIDE_HOST=$(kubectl get node "$NODE_NAME" -o jsonpath='{.status.addresses[?(@.type=="InternalIP")].address}')
      if [ $? -ne 0 ]; then
        echo "Outside (i.e. cluster-external access) host lookup command failed"
      else
        OUTSIDE_PORT=3240${KAFKA_BROKER_ID}
        SEDS+=("s|#init#advertised.listeners=OUTSIDE://#init#|advertised.listeners=OUTSIDE://${OUTSIDE_HOST}:${OUTSIDE_PORT}|")
        ANNOTATIONS="$ANNOTATIONS kafka-listener-outside-host=$OUTSIDE_HOST kafka-listener-outside-port=$OUTSIDE_PORT"
      fi

      if [ ! -z "$LABELS" ]; then
        kubectl -n $POD_NAMESPACE label pod $POD_NAME $LABELS || echo "Failed to label $POD_NAMESPACE.$POD_NAME - RBAC issue?"
      fi
      if [ ! -z "$ANNOTATIONS" ]; then
        kubectl -n $POD_NAMESPACE annotate pod $POD_NAME $ANNOTATIONS || echo "Failed to annotate $POD_NAMESPACE.$POD_NAME - RBAC issue?"
      fi
    }
    printf '%s\n' "${SEDS[@]}" | sed -f - /etc/kafka-configmap/server.properties &gt; /etc/kafka/server.properties.tmp
    [ $? -eq 0 ] &amp;&amp; mv /etc/kafka/server.properties.tmp /etc/kafka/server.properties

  server.properties: |-
    ############################# Log Basics #############################

    # A comma seperated list of directories under which to store log files
    # Overrides log.dir
    log.dirs=/var/lib/kafka/data/topics

    # The default number of log partitions per topic. More partitions allow greater
    # parallelism for consumption, but this will also result in more files across
    # the brokers.
    num.partitions=1

    default.replication.factor=3

    min.insync.replicas=2

    auto.create.topics.enable=true

    # The number of threads per data directory to be used for log recovery at startup and flushing at shutdown.
    # This value is recommended to be increased for installations with data dirs located in RAID array.
    #num.recovery.threads.per.data.dir=1

    ############################# Server Basics #############################

    # The id of the broker. This must be set to a unique integer for each broker.
    #init#broker.id=#init#

    #init#broker.rack=#init#

    ############################# Socket Server Settings #############################

    # The address the socket server listens on. It will get the value returned from
    # java.net.InetAddress.getCanonicalHostName() if not configured.
    #   FORMAT:
    #     listeners = listener_name://host_name:port
    #   EXAMPLE:
    #     listeners = PLAINTEXT://your.host.name:9092
    #listeners=PLAINTEXT://:9092
    listeners=OUTSIDE://:9094,PLAINTEXT://:9092

    # Hostname and port the broker will advertise to producers and consumers. If not set,
    # it uses the value for "listeners" if configured.  Otherwise, it will use the value
    # returned from java.net.InetAddress.getCanonicalHostName().
    #advertised.listeners=PLAINTEXT://your.host.name:9092
    #init#advertised.listeners=OUTSIDE://#init#,PLAINTEXT://:9092

    # Maps listener names to security protocols, the default is for them to be the same. See the config documentation for more details
    #listener.security.protocol.map=PLAINTEXT:PLAINTEXT,SSL:SSL,SASL_PLAINTEXT:SASL_PLAINTEXT,SASL_SSL:SASL_SSL
    listener.security.protocol.map=PLAINTEXT:PLAINTEXT,SSL:SSL,SASL_PLAINTEXT:SASL_PLAINTEXT,SASL_SSL:SASL_SSL,OUTSIDE:PLAINTEXT
    inter.broker.listener.name=PLAINTEXT

    # The number of threads that the server uses for receiving requests from the network and sending responses to the network
    #num.network.threads=3

    # The number of threads that the server uses for processing requests, which may include disk I/O
    #num.io.threads=8

    # The send buffer (SO_SNDBUF) used by the socket server
    #socket.send.buffer.bytes=102400

    # The receive buffer (SO_RCVBUF) used by the socket server
    #socket.receive.buffer.bytes=102400

    # The maximum size of a request that the socket server will accept (protection against OOM)
    #socket.request.max.bytes=104857600

    ############################# Internal Topic Settings  #############################
    # The replication factor for the group metadata internal topics "__consumer_offsets" and "__transaction_state"
    # For anything other than development testing, a value greater than 1 is recommended for to ensure availability such as 3.
    #offsets.topic.replication.factor=1
    #transaction.state.log.replication.factor=1
    #transaction.state.log.min.isr=1

    ############################# Log Flush Policy #############################

    # Messages are immediately written to the filesystem but by default we only fsync() to sync
    # the OS cache lazily. The following configurations control the flush of data to disk.
    # There are a few important trade-offs here:
    #    1. Durability: Unflushed data may be lost if you are not using replication.
    #    2. Latency: Very large flush intervals may lead to latency spikes when the flush does occur as there will be a lot of data to flush.
    #    3. Throughput: The flush is generally the most expensive operation, and a small flush interval may lead to excessive seeks.
    # The settings below allow one to configure the flush policy to flush data after a period of time or
    # every N messages (or both). This can be done globally and overridden on a per-topic basis.

    # The number of messages to accept before forcing a flush of data to disk
    #log.flush.interval.messages=10000

    # The maximum amount of time a message can sit in a log before we force a flush
    #log.flush.interval.ms=1000

    ############################# Log Retention Policy #############################

    # The following configurations control the disposal of log segments. The policy can
    # be set to delete segments after a period of time, or after a given size has accumulated.
    # A segment will be deleted whenever *either* of these criteria are met. Deletion always happens
    # from the end of the log.

    # https://cwiki.apache.org/confluence/display/KAFKA/KIP-186%3A+Increase+offsets+retention+default+to+7+days
    offsets.retention.minutes=10080

    # The minimum age of a log file to be eligible for deletion due to age
    log.retention.hours=-1

    # A size-based retention policy for logs. Segments are pruned from the log unless the remaining
    # segments drop below log.retention.bytes. Functions independently of log.retention.hours.
    #log.retention.bytes=1073741824

    # The maximum size of a log segment file. When this size is reached a new log segment will be created.
    #log.segment.bytes=1073741824

    # The interval at which log segments are checked to see if they can be deleted according
    # to the retention policies
    #log.retention.check.interval.ms=300000

    ############################# Zookeeper #############################

    # Zookeeper connection string (see zookeeper docs for details).
    # This is a comma separated host:port pairs, each corresponding to a zk
    # server. e.g. "127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002".
    # You can also append an optional chroot string to the urls to specify the
    # root directory for all kafka znodes.
    zookeeper.connect=zoo-0.zoo:2181,zoo-1.zoo:2181,zoo-2.zoo:2181

    # Timeout in ms for connecting to zookeeper
    #zookeeper.connection.timeout.ms=6000


    ############################# Group Coordinator Settings #############################

    # The following configuration specifies the time, in milliseconds, that the GroupCoordinator will delay the initial consumer rebalance.
    # The rebalance will be further delayed by the value of group.initial.rebalance.delay.ms as new members join the group, up to a maximum of max.poll.interval.ms.
    # The default value for this is 3 seconds.
    # We override this to 0 here as it makes for a better out-of-the-box experience for development and testing.
    # However, in production environments the default value of 3 seconds is more suitable as this will help to avoid unnecessary, and potentially expensive, rebalances during application startup.
    #group.initial.rebalance.delay.ms=0

  log4j.properties: |-
    # Unspecified loggers and loggers with additivity=true output to server.log and stdout
    # Note that INFO only applies to unspecified loggers, the log level of the child logger is used otherwise
    log4j.rootLogger=INFO, stdout

    log4j.appender.stdout=org.apache.log4j.ConsoleAppender
    log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
    log4j.appender.stdout.layout.ConversionPattern=[%d] %p %m (%c)%n

    log4j.appender.kafkaAppender=org.apache.log4j.DailyRollingFileAppender
    log4j.appender.kafkaAppender.DatePattern='.'yyyy-MM-dd-HH
    log4j.appender.kafkaAppender.File=${kafka.logs.dir}/server.log
    log4j.appender.kafkaAppender.layout=org.apache.log4j.PatternLayout
    log4j.appender.kafkaAppender.layout.ConversionPattern=[%d] %p %m (%c)%n

    log4j.appender.stateChangeAppender=org.apache.log4j.DailyRollingFileAppender
    log4j.appender.stateChangeAppender.DatePattern='.'yyyy-MM-dd-HH
    log4j.appender.stateChangeAppender.File=${kafka.logs.dir}/state-change.log
    log4j.appender.stateChangeAppender.layout=org.apache.log4j.PatternLayout
    log4j.appender.stateChangeAppender.layout.ConversionPattern=[%d] %p %m (%c)%n

    log4j.appender.requestAppender=org.apache.log4j.DailyRollingFileAppender
    log4j.appender.requestAppender.DatePattern='.'yyyy-MM-dd-HH
    log4j.appender.requestAppender.File=${kafka.logs.dir}/kafka-request.log
    log4j.appender.requestAppender.layout=org.apache.log4j.PatternLayout
    log4j.appender.requestAppender.layout.ConversionPattern=[%d] %p %m (%c)%n

    log4j.appender.cleanerAppender=org.apache.log4j.DailyRollingFileAppender
    log4j.appender.cleanerAppender.DatePattern='.'yyyy-MM-dd-HH
    log4j.appender.cleanerAppender.File=${kafka.logs.dir}/log-cleaner.log
    log4j.appender.cleanerAppender.layout=org.apache.log4j.PatternLayout
    log4j.appender.cleanerAppender.layout.ConversionPattern=[%d] %p %m (%c)%n

    log4j.appender.controllerAppender=org.apache.log4j.DailyRollingFileAppender
    log4j.appender.controllerAppender.DatePattern='.'yyyy-MM-dd-HH
    log4j.appender.controllerAppender.File=${kafka.logs.dir}/controller.log
    log4j.appender.controllerAppender.layout=org.apache.log4j.PatternLayout
    log4j.appender.controllerAppender.layout.ConversionPattern=[%d] %p %m (%c)%n

    log4j.appender.authorizerAppender=org.apache.log4j.DailyRollingFileAppender
    log4j.appender.authorizerAppender.DatePattern='.'yyyy-MM-dd-HH
    log4j.appender.authorizerAppender.File=${kafka.logs.dir}/kafka-authorizer.log
    log4j.appender.authorizerAppender.layout=org.apache.log4j.PatternLayout
    log4j.appender.authorizerAppender.layout.ConversionPattern=[%d] %p %m (%c)%n

    # Change the two lines below to adjust ZK client logging
    log4j.logger.org.I0Itec.zkclient.ZkClient=INFO
    log4j.logger.org.apache.zookeeper=INFO

    # Change the two lines below to adjust the general broker logging level (output to server.log and stdout)
    log4j.logger.kafka=INFO
    log4j.logger.org.apache.kafka=INFO

    # Change to DEBUG or TRACE to enable request logging
    log4j.logger.kafka.request.logger=WARN, requestAppender
    log4j.additivity.kafka.request.logger=false

    # Uncomment the lines below and change log4j.logger.kafka.network.RequestChannel$ to TRACE for additional output
    # related to the handling of requests
    #log4j.logger.kafka.network.Processor=TRACE, requestAppender
    #log4j.logger.kafka.server.KafkaApis=TRACE, requestAppender
    #log4j.additivity.kafka.server.KafkaApis=false
    log4j.logger.kafka.network.RequestChannel$=WARN, requestAppender
    log4j.additivity.kafka.network.RequestChannel$=false

    log4j.logger.kafka.controller=TRACE, controllerAppender
    log4j.additivity.kafka.controller=false

    log4j.logger.kafka.log.LogCleaner=INFO, cleanerAppender
    log4j.additivity.kafka.log.LogCleaner=false

    log4j.logger.state.change.logger=TRACE, stateChangeAppender
    log4j.additivity.state.change.logger=false

    # Change to DEBUG to enable audit log for the authorizer
    log4j.logger.kafka.authorizer.logger=WARN, authorizerAppender
    log4j.additivity.kafka.authorizer.logger=false
</code></pre>

<p>As per this: <a href="https://stackoverflow.com/questions/38065492/launching-multiple-kafka-brokers-fails">Launching multiple Kafka brokers fails</a>, it's an issue with <code>log.dirs</code> in your <code>server.properties</code> where it can't be the same for all your brokers or it can't be shared.</p>

<p>You can probably use the <code>${HOSTNAME##*-}</code> bash environment setting to modify your container entrypoint script that in of itself modifies your <code>server.properties</code> before the start, but the downside of that is that you are going to have to rebuild your Docker image.</p>

<p>Another strategy using StatefulSets is described here: <a href="https://stackoverflow.com/questions/41731947/how-to-pass-args-to-pods-based-on-ordinal-index-in-statefulsets">How to pass args to pods based on Ordinal Index in StatefulSets?</a>. But you will also have to make changes on how the Kafka entrypoint is called.</p>

<p>You could also try using completely different volumes for each of your Kafka broker pods.</p>
