A handler script for updating /etc/hosts with Serf.

update_hosts.sh

#!/bin/sh

set -e

export PATH=/usr/local/bin:/usr/bin:/bin

read name address role tags

file=/etc/hosts
tmp_file=/tmp/hosts.tmp
lock_file=/tmp/hosts.lock

active_members=$(serf members | grep 'alive' | cut -d ':' -f1 | awk '{print $2"\t"$1}')

while [ -f $lock_file ] ; do sleep 1 ; done

touch $lock_file

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

  hosts=$(grep -v '^#' $file)

  echo -e "$hosts\n$active_members" | sort -n | uniq > $tmp_file

  mv $tmp_file $file \
    && echo "$name successfully added to $file"

elif [ $SERF_EVENT = 'member-leave' -o $SERF_EVENT = 'member-failed' ] ; then

  hosts=$(grep -v '^#' $file | grep -v "^$address[[:blank:]]")

  echo -e "$hosts\n$active_members" | sort -n | uniq > $tmp_file

  mv $tmp_file $file \
    && echo "$name successfully removed from $file"

fi

rm -f $lock_file