init.sh

#!/bin/bash
set -e

COMMAND="$@"
INIT_NAME=${INIT_NAME:-myapp}
HEALTH_PORT=${HEALTH_PORT:-8080}
HEALTH_PATH=${HEALTH_PATH:-ping}
HEALTH_PERIOD_SECONDS=${HEALTH_PERIOD_SECONDS:-1}
HEALTHY_INDICATOR=${HEALTHY_INDICATOR:-/tmp/ready}
APP_STOP_DELAY=${APP_STOP_DELAY:-5}
SIGNAL_RECIEVED_INDICATOR=$(mktemp --dry-run /tmp/$INIT_NAME-teminating.XXXXXX)

_terminating() {
  touch ${SIGNAL_RECIEVED_INDICATOR}
  rm  -f ${HEALTHY_INDICATOR}
}

_term() {
  ls /tmp
  echo "Caught SIGTERM signal!"
  _terminating
  sleep ${APP_STOP_DELAY}
  echo "stopping the child ${child}"
  kill -9 ${child}
}

_health_check() {
  while [ ! -f ${SIGNAL_RECIEVED_INDICATOR} ]
  do
    # either you check the port (nc version) or you are checking the http call (curl version)
    # if ! nc -vz locahost ${HEALTH_PORT} >/dev/null 2>&1
    if ! curl --fail --silent http://localhost:${HEALTH_PORT}/${HEALTH_PATH} > /dev/null
    then
      rm  -f ${HEALTHY_INDICATOR}
    else
      touch rm  -f ${HEALTHY_INDICATOR}
    fi
    sleep ${HEALTH_PERIOD_SECONDS}
  done
}

trap _term SIGTERM
${COMMAND} &
child=$!

_health_check &
wait "${child}"
_terminating