docker-entrypoint.sh

#!/bin/bash

# Batch modification
/etc/init.d/ssh start

# Set memlock limit to unlimited (before set -e)
ulimit -l unlimited 2&>/dev/null

set -e

[ "$DEBUG" ] && set -x

# first arg is `-f` or `--some-option`
# or there are no args
if [ "$#" -eq 0 ] || [ "${1#-}" != "$1" ]; then
    set -- cassandra -f "$@"
fi

# allow the container to be started with `--user`
if [ "$1" = 'cassandra' -a "$(id -u)" = '0' ]; then
    find /var/lib/cassandra /var/log/cassandra "$CASSANDRA_CONFIG" \! -user cassandra -exec chown cassandra '{}' + 
    exec gosu cassandra "$BASH_SOURCE" "$@"
fi

_ip_address() {
    # scrape the first non-localhost IP address of the container
    # in Swarm Mode, we often get two IPs -- the container IP, and the (shared) VIP, and the container IP should always be first
    ip address | awk '$1 == "inet" && $NF != "lo" { gsub(/\/.+$/, "", $2); print $2; exit }'
}

# "sed -i", but without "mv" (which doesn't work on a bind-mounted file, for example)
_sed-in-place() {
    local filename="$1"; shift
    local tempFile
    tempFile="$(mktemp)"
    sed "$@" "$filename" > "$tempFile"
    cat "$tempFile" > "$filename"
    rm "$tempFile"
}

# usage:
#   config_injection CASSANDRA $CASSANDRA_CONFIG/cassandra.yaml
#   config_injection ELASTICSEARCH $CASSANDRA_CONFIG/elasticsearch.yml
config_injection() {

    local filename="$2";
    local filter
    local tempFile

    for v in $(compgen -v "${1}__"); do
     echo "v=$v"
     val="${!v}"
     if [ "$val" ]; then
        var=$(echo ${v#"${1}"}|sed 's/__/\./g')
        if is_num ${val}; then
          filter="${var}=${val}"
        else
          case ${val} in
            true)  filter="${var}=true";;
            false) filter="${var}=false";;
            *)     filter="${var}=\"${val}\"";;
          esac
        fi
       
        tempFile="$(mktemp)"
        if [[ "$(yq --yaml-output . $filename | wc -l | xargs)" == 0 ]]; then
            echo "${filter:1}" | sed 's/=/: /g' > "$tempFile"
        else
           yq --yaml-output ". * $(echo "${filter};" | gron -u)" $filename > "$tempFile"
        fi
        cat "$tempFile" > $filename
        rm "$tempFile"
     fi
    done

    if [ "$DEBUG" ]; then
       echo "config_injection $filename:"
       cat "$filename"
    fi
}

is_num() {
  re='^-?[0-9]+$'
  [[ $1 =~ $re ]] && true
}

if [ "$1" = 'cassandra' ]; then

  # init script (allows to define env var before conf generation)
  for f in /docker-entrypoint-init.d/*; do
    case "$f" in
        *.sh)     echo "$0: running $f"; . "$f" ;;
        *)        echo "$0: ignoring $f" ;;
    esac
  done
  
  # btw, it has been already set in Dockerfile
  : ${CASSANDRA_DAEMON:='org.apache.cassandra.service.ElassandraDaemon'}
  export CASSANDRA_DAEMON

    : ${CASSANDRA_RPC_ADDRESS='0.0.0.0'}

    : ${CASSANDRA_LISTEN_ADDRESS='auto'}
    if [ "$CASSANDRA_LISTEN_ADDRESS" = 'auto' ]; then
        CASSANDRA_LISTEN_ADDRESS="$(_ip_address)"
    fi

    : ${CASSANDRA_BROADCAST_ADDRESS="$CASSANDRA_LISTEN_ADDRESS"}

    if [ "$CASSANDRA_BROADCAST_ADDRESS" = 'auto' ]; then
        CASSANDRA_BROADCAST_ADDRESS="$(_ip_address)"
    fi
    : ${CASSANDRA_BROADCAST_RPC_ADDRESS:=$CASSANDRA_BROADCAST_ADDRESS}

    if [ -n "${CASSANDRA_NAME:+1}" ]; then
        : ${CASSANDRA_SEEDS:="cassandra"}
    fi
    : ${CASSANDRA_SEEDS:="$CASSANDRA_BROADCAST_ADDRESS"}

    _sed-in-place "$CASSANDRA_CONFIG/cassandra.yaml" -r 's/(- seeds:).*/\1 "'"$CASSANDRA_SEEDS"'"/'

    for yaml in \
        broadcast_address \
        broadcast_rpc_address \
        cluster_name \
        endpoint_snitch \
        listen_address \
        num_tokens \
        rpc_address \
        start_rpc \
    ; do
        var="CASSANDRA_${yaml^^}"
        val="${!var}"
        if [ "$val" ]; then
            _sed-in-place "$CASSANDRA_CONFIG/cassandra.yaml" -r 's/^(# )?('"$yaml"':).*/\2 '"$val"'/'
        fi
    done

    for rackdc in dc rack prefer_local dc_suffix; do
        var="CASSANDRA_${rackdc^^}"
        val="${!var}"
        if [ "$val" ]; then
            _sed-in-place "$CASSANDRA_CONFIG/cassandra-rackdc.properties" -r 's/^('"$rackdc"'=).*/\1 '"$val"'/'
        fi
    done


  config_injection CASSANDRA $CASSANDRA_CONFIG/cassandra.yaml
  config_injection ELASTICSEARCH $CASSANDRA_CONFIG/elasticsearch.yml

  if [ "$LOCAL_JMX" = "no" ]; then
       export JVM_OPTS="$JVM_OPTS -Djava.rmi.server.hostname=$POD_IP"
  fi
  
  : ${CASSANDRA_CGROUP_MEMORY_LIMIT='false'}

  # Specifies if heap size should be limited by cgroup constraints
  if [ "${CASSANDRA_CGROUP_MEMORY_LIMIT}" = 'true' ]; then
     export JVM_OPTS="$JVM_OPTS -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap -XX:MaxRAMFraction=2"
  fi  
fi

exec "$@"