demo/docker_files/start-kafka.sh

#!/bin/bash

if [[ -z "$KAFKA_PORT" ]]; then
    export KAFKA_PORT=9092
fi
if [[ -z "$KAFKA_ADVERTISED_PORT" ]]; then
    export KAFKA_ADVERTISED_PORT=$(docker port `hostname` $KAFKA_PORT | sed -r "s/.*:(.*)/\1/g")
fi
if [[ -z "$KAFKA_BROKER_ID" ]]; then
    # By default auto allocate broker ID
    #export KAFKA_BROKER_ID=-1
    export KAFKA_BROKER_ID=1
fi
#if [[ -z "$KAFKA_LOG_DIRS" ]]; then
    #export KAFKA_LOG_DIRS="/kafka/kafka-logs-$HOSTNAME"
    export KAFKA_LOG_DIRS="/kafka/kafka-logs"
#fi
if [[ -z "$KAFKA_ZOOKEEPER_CONNECT" ]]; then
    export KAFKA_ZOOKEEPER_CONNECT=$(env | grep ZK.*PORT_2181_TCP= | sed -e 's|.*tcp://||' | paste -sd ,)
fi

if [[ -n "$KAFKA_HEAP_OPTS" ]]; then
    sed -r -i "s/(export KAFKA_HEAP_OPTS)=\"(.*)\"/\1=\"$KAFKA_HEAP_OPTS\"/g" $KAFKA_HOME/bin/kafka-server-start.sh
    unset KAFKA_HEAP_OPTS
fi

if [[ -z "$KAFKA_ADVERTISED_HOST_NAME" && -n "$HOSTNAME_COMMAND" ]]; then
    export KAFKA_ADVERTISED_HOST_NAME=$(eval $HOSTNAME_COMMAND)
fi

for VAR in `env`
do
  if [[ $VAR =~ ^KAFKA_ && ! $VAR =~ ^KAFKA_HOME ]]; then
    kafka_name=`echo "$VAR" | sed -r "s/KAFKA_(.*)=.*/\1/g" | tr '[:upper:]' '[:lower:]' | tr _ .`
    env_var=`echo "$VAR" | sed -r "s/(.*)=.*/\1/g"`
    if egrep -q "(^|^#)$kafka_name=" $KAFKA_HOME/config/server.properties; then
        sed -r -i "s@(^|^#)($kafka_name)=(.*)@\2=${!env_var}@g" $KAFKA_HOME/config/server.properties #note that no config values may contain an '@' char
    else
        echo "$kafka_name=${!env_var}" >> $KAFKA_HOME/config/server.properties
    fi
  fi
done

if [[ -n "$CUSTOM_INIT_SCRIPT" ]] ; then
  eval $CUSTOM_INIT_SCRIPT
fi


KAFKA_PID=0

# see https://medium.com/@gchudnov/trapping-signals-in-docker-containers-7a57fdda7d86#.bh35ir4u5
term_handler() {
  echo 'Stopping Kafka....'
  if [ $KAFKA_PID -ne 0 ]; then
    kill -s TERM "$KAFKA_PID"
    wait "$KAFKA_PID"
  fi
  echo 'Kafka stopped.'
  exit
}


# Capture kill requests to stop properly
trap "term_handler" SIGHUP SIGINT SIGTERM
create-topics.sh &
$KAFKA_HOME/bin/kafka-server-start.sh $KAFKA_HOME/config/server.properties &
KAFKA_PID=$!

wait "$KAFKA_PID"