Kumogata+Serf- event_handler.rb

event_handler.rb

#!/usr/bin/env ruby
require 'fileutils'
require 'tempfile'
require 'socket'

HOSTS_PATH = '/etc/hosts'
EVENTS     = %w(member-join member-leave member-failed)
EXCLUDES   = %w(127.0.0.1)

def open_hosts
  open(HOSTS_PATH) do |f|
    f.flock(File::LOCK_EX)
    yield(f)
  end
end

def current_hosts(f)
  rgx = /\A(#{EXCLUDES.map {|i| Regexp.escape(i) }.join('|')})\s+/
  f.read.split("\n").grep(rgx).join("\n")
end

def serf_members
  `serf members | grep -v #{Socket.gethostname}`.split("\n").map {|i|
    i.split(/[\s:]+/)[0..1].reverse
  }.map {|i| i.join("\t") }.join("\n")
end

def update_hosts
  open_hosts do |hosts|
    Tempfile.open(File.basename(__FILE__)) do |tmp|
      tmp.puts current_hosts(hosts)
      tmp.puts serf_members
      tmp.flush
      FileUtils.copy(tmp.path, hosts.path)
    end
  end
end

if EVENTS.include?(ENV['SERF_EVENT'])
  update_hosts
end