A quick & dirty script to spin up an nginx container that will load balance requests to a Kubernetes cluster

run_nginx_lb.sh

#!/bin/bash

print_help() {
    echo
    echo "Usage: $(basename $0) -p port [-p port] -s server [-s server]"
    echo
}

TMP_DIR="/tmp/nginx_conf_$$"

while getopts "p:s:" OPT; do
    case "${OPT}" in
        p) PORTS="${OPTARG},${PORTS}";;
        s) SERVERS="${OPTARG},${SERVERS}";;
        h) print_help; exit 1;;
        :) print_help; exit 1;;
    esac
done

# bounce if wrong number of args
[[ ${OPTIND} -eq 1 ]] && print_help && exit 1

shift "$((OPTIND - 1))"

# make a temp dir for nginx conf
mkdir -p ${TMP_DIR}/conf

# dynamically build our nginx conf file
cat << EOF > ${TMP_DIR}/conf/nginx.conf
events {}
stream {
    log_format basic '\$remote_addr [\$time_local] '
                     '\$protocol \$status \$bytes_sent \$bytes_received '
                     '\$session_time';

    access_log /dev/stdout basic;
EOF

# build our upstream apps
APP_NUMBER="1"

while read PORT; do

cat << EOF >> ${TMP_DIR}/conf/nginx.conf
    upstream app${APP_NUMBER} {
EOF
    while read SERVER; do

cat << EOF >> ${TMP_DIR}/conf/nginx.conf
        server ${SERVER}:${PORT};
EOF

    done < <(echo ${SERVERS} | sed 's/,$//' | tr ',' '\n' | sort -u)

cat << EOF >> ${TMP_DIR}/conf/nginx.conf
    }
EOF

    let APP_NUMBER+=1

done < <(echo ${PORTS} | sed 's/,$//' | tr ',' '\n' | sort -u)

# reset the app number
APP_NUMBER="1"

# build our servers
while read PORT; do
cat << EOF >> ${TMP_DIR}/conf/nginx.conf
    server {
        listen ${PORT};
        proxy_pass app${APP_NUMBER};
    }
EOF

    let APP_NUMBER+=1

done < <(echo ${PORTS} | sed 's/,$//' | tr ',' '\n' | sort -u)

# close out file
cat << EOF >> ${TMP_DIR}/conf/nginx.conf
}
EOF

# create our port flags for docker command
PORT_ARGS=""

while read PORT; do
    [[ -n ${PORT_ARGS} ]] && PORT_ARGS="-p ${PORT}:${PORT} ${PORT_ARGS}" || PORT_ARGS="-p ${PORT}:${PORT}"
done < <(echo ${PORTS} | sed 's/,$//' | tr ',' '\n' | sort -u)

docker run ${PORT_ARGS} -v ${TMP_DIR}/conf:/tmp/conf nginx nginx -c /tmp/conf/nginx.conf -g "daemon off;"

rm -Rf ${TMP_DIR}