cassandra-entrypoint.sh

#!/bin/bash
set -e

# 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 "$CASSANDRA_CONF" /var/lib/cassandra /var/log/cassandra \
        \! -user cassandra -exec chown cassandra '{}' +
    exec gosu cassandra "$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"
}

if [ "$1" = 'cassandra' ]; then
    : ${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 "$CASSANDRA_CONF/cassandra.yaml" \
        -r 's/(- seeds:).*/\1 "'"$CASSANDRA_SEEDS"'"/'

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

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

exec "$@"