Manage /etc/hosts using serf

serf_host_handler.sh

#!/bin/bash
HOST_FILE=/etc/hosts

hn=`hostname`
touch $HOST_FILE
lines=`cat`


appendIfNotPresent() {
  if [ "$2" == "$hn" ]; then
    echo "not writing own hostname"
    return
  fi
  entry="$1 $2"
  (
    flock -n 9 || exit 1
    if grep -Fxq "$entry" $HOST_FILE; then
      echo "entry already exists, not re-adding"
    else
      echo $entry >> $HOST_FILE
    echo "wrote $enty to $HOST_FILE"
    fi
  ) 9>/var/lock/hosts-flock-lock
}

removeIfPresent() {
  if [ "$2" == "$hn" ]; then
    return
  fi
  entry="$1 $2"
  (
    flock -n 9 || exit 1
    sed -i \"/$entry/d\" $HOST_FILE
  ) 9>/var/lock/hosts-flock-lock
}


readarray -t lines <<<"$lines"

if [ "$SERF_EVENT" == "member-join" ]; then

  for member in "${lines[@]}"; do
    member_array=($member)
    appendIfNotPresent "${member_array[1]}" "${member_array[0]}"
  done

elif [[ ( "$SERF_EVENT" == "member-leave" ) || ( "$SERF_EVENT" == "member-failed" ) ]]; then

  for member in "${lines[@]}"; do
    member_array=($member)
    removeIfPresent ${member_array[1]} ${member_array[0]}
  done

else
  echo "unknown event"
fi