#!/usr/bin/python
"""
/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.	 
 */
"""
# XXXstroucki: why not use something like supervise instead?

import os
import sys
import getopt
import subprocess
import time

SLEEP_INTERVAL=10
TASHI_PATH="/usr/local/tashi/"
LOG_FILE="/var/log/nodemanager.log"

"""
/* This function changes (on Linux!) its oom scoring, to make it
 * unattractive to kill
 */
"""
def make_invincible():
	# dependent on linux
	try:
		oom_adj_fd = os.open("/proc/self/oom_adj", os.O_WRONLY)
	except IOError:
		pass
	else:
		os.write(oom_adj_fd, "-17\n")
		os.close(oom_adj_fd)

"""
/* This function resets (on Linux!) its oom scoring to default
 */
"""
def make_vulnerable():
	# dependent on linux
	try:
		oom_adj_fd = os.open("/proc/self/oom_adj", os.O_WRONLY)
	except IOError:
		pass
	else:
		os.write(oom_adj_fd, "0\n")
		os.close(oom_adj_fd)

def main(argv=None):
	if argv is None:
		argv = sys.argv
	try:
		opts, args = getopt.getopt(argv[1:], "f", ["foreground"])
	except getopt.GetoptError, err:
		# print help information and exit:
		print str(err) # will print something like "option -a not recognized"
		# usage()
		return 2
	foreground = False
	for o, a in opts:
		if o in ("-f", "--foreground"):
			foreground = True
		else:
			assert False, "unhandled option"
	if foreground == False:
		pid = os.fork();
		if pid != 0:
			os._exit(0)
		os.close(0)
		os.close(1)
		os.close(2)

	# adjust oom preference
	make_invincible()

	# configure environment of children
	env = {"PYTHONPATH":TASHI_PATH+"/src"}
	while True:
		pid = os.fork();
		if pid == 0:
			# child
			# nodemanagers are vulnerable, not the supervisor
			make_vulnerable()
			if foreground == False:
				try:
					lfd = os.open(LOG_FILE, os.O_APPEND|os.O_CREAT|os.O_WRONLY)
				except IOError:
					lfd = os.open("/dev/null", os.O_WRONLY)
				# make this fd stdout and stderr
				os.dup2(lfd, 1)
				os.dup2(lfd, 2)
				# close stdin
				os.close(0)
			os.chdir(TASHI_PATH)
			os.execle("./bin/nodemanager.py", "./bin/nodemanager.py", env)
			os._exit(-1)
		# sleep before checking child status
		time.sleep(SLEEP_INTERVAL)
		os.waitpid(pid, 0)
	return 0

if __name__ == "__main__":
	sys.exit(main())