#!/usr/bin/env ruby
#
#  watchdog.rb: Watchdog component.
#
#  Copyright (C) 2011 VMware, Inc.
# 
#  Permission is hereby granted, free of charge, to any person obtaining a copy
#  of this software and associated documentation files (the "Software"), to deal
#  in the Software without restriction, including without limitation the rights
#  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
#  copies of the Software, and to permit persons to whom the Software is
#  furnished to do so, subject to the following conditions:
#  
#  The above copyright notice and this permission notice shall be included in
#  all copies or substantial portions of the Software.
# 
#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
#  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
#  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
#  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
#  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
#  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
#  THE SOFTWARE.

require 'thread'
require 'ffi-rzmq'
require 'socket'

trap("INT") { exit }
trap("TERM") { exit }
def raise_if_error(rc)
  unless ZMQ::Util.resultcode_ok?(rc)
    raise "ZMQ Error: #{ZMQ::Util.error_string}"
  end
end

if ARGV.length != 1
  print "usage: watchdog <notifier-host>\n"
  exit 1
end

notifier_ep = "tcp://#{ARGV[0]}:7770"
control_ep = "tcp://*:7772"

ctx = ZMQ::Context.new()
notifier_sock = ctx.socket(ZMQ::PUB)
rc = notifier_sock.connect(notifier_ep)
raise_if_error(rc)

control_sock = ctx.socket(ZMQ::PULL)
rc = control_sock.bind(control_ep)
raise_if_error(rc)

poller = ZMQ::Poller.new
poller.register_readable(control_sock)

children = {}

#  Delete process if it went away
trap("CHLD") do
  pid = Process.wait
  children.each do |k, v|
    if v[:pid] == pid
      children.delete(k)
    end
  end
end

#  Kill any children on exit
trap("TERM") do
  children.each do |k, v|
    Process.kill("KILL", v[:pid])
  end
end

#
#  Main loop
#
loop do
  ready = poller.poll(1)

  #  Process commands, if any.
  if (ready == 1 && poller.readables.include?(control_sock))
    msg = ''
    rc = control_sock.recv_string(msg)
    raise_if_error(rc)
    if (msg =~ /^START (.+)$/)
      command = $1
      key = command.split()[0]
      unless children.has_key?(key)
        exec_command = "./" + key
        if File.exists?(exec_command) && File.executable?(exec_command)
          children[key] = {}
          children[key][:pid] = Process.spawn("./" + command)
          children[key][:command] = command
        end
      end
    elsif (msg =~ /^STOP (.+)$/)
      command = $1
      key = command.split()[0]
      if children.has_key?(key)
        Process.kill("KILL", children[key][:pid])
        while children.has_key?(key)
          # nothing  
        end
      end
    end
  #  Otherwise, send out status messages to notifier.
  else
    status = "WATCHDOG ALIVE " + Socket.gethostname + " " + Time.now.to_f.to_s
    rc = notifier_sock.send_string(status)
    raise_if_error(rc)
    children.each do |k, v|
      status = "WATCHDOG RUNNING " + Socket.gethostname + \
        " " + Time.now.to_f.to_s + " " + v[:command]
      rc = notifier_sock.send_string(status)
      raise_if_error(rc)
    end
  end
end