reload_haproxy.sh

#!/bin/bash
#
# Reloads HAProxy and kills the old instances kept alive by open connections.
#
# Old HAProxy instances will only be killed if they're:
#     * bound to ports in CHOPPABLE_PORTS
#     * not the active HAProxy process, as defined by PID_FILE

CONF=/etc/haproxy/haproxy.cfg
PID_FILE=/run/haproxy.pid
# Ports HAProxy is listening on
LISTEN_PORTS=80,443,6001
# Ports we're willing to drop connections on
CHOPPABLE_PORTS=6001

if [[ "$EUID" -ne 0 ]] ; then
  echo Must run as root
  exit 1
fi

validate_config() {
  msg=$(haproxy -c -f "${CONF}" 2>&1)
  code=$?
  if [[ "${code}" -ne 0 ]] ; then
    echo Invalid config file: "${CONF}"
    echo "${msg}"
    exit 2
  fi
}

reload() {
  systemctl reload haproxy
}

kill_dangling_haproxy_processes() {
  listeners=($(lsof -i tcp:${LISTEN_PORTS} | tail -n +2 | grep -i listen | awk '{ print $2 }'))
  disposable=($(lsof -i tcp:${CHOPPABLE_PORTS} | tail -n +2 | grep -i established | awk '{ print $2 }'))

  for pid in "${disposable[@]}" ; do
    if [[ "${pid}" -eq "${active_worker}" ]] ; then
      echo "Established websocket connection being served by new worker ${pid}, skipping."
    fi

    for listener in "${listeners[@]}" ; do
      if [[ "${pid}" -eq "${listener}" ]] ; then
        echo "Established websocket connection being served by a worker ${pid} bound to listening ports, skipping."
      fi
    done

    echo "Killing worker ${pid}" && kill ${pid}
    if [[ $? -ne 0 ]] ; then
      echo "Failed to kill ${pid} with code $?"
      exit 3
    fi
  done
}

validate_config
reload
kill_dangling_haproxy_processes