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#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (C) 2017 Pavel Raiskup
#
# This program accepts one argument IP or HOSTNAME. First try to connect to the
# HOSTNAME as 'root' user. If cloud-init scripts instruct us to use different
# user than 'root', switch to that user and check again. In the end, print the
# successful username on stdout.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
from re import compile as re_compile
import sys
from os import devnull
from threading import Thread, Event
from argparse import ArgumentParser
from subprocess import Popen, PIPE
import logging
handler = logging.StreamHandler()
log = logging.getLogger()
log.setLevel(logging.INFO)
log.addHandler(handler)
# create console handler and set level to debug
ssh = [
'ssh',
'-o', 'StrictHostKeyChecking=no',
'-o', 'UserKnownHostsFile=/dev/null',
'-o', 'PasswordAuthentication=no',
'-o', 'ConnectTimeout=10',
]
expected_output = 'foobar'
inner_cmd = 'echo ' + expected_output
class Checker(Thread):
user = 'root'
daemon = True
user_re = '[a-zA-Z0-9_.][a-zA-Z0-9_.-]*[$]?'
re_clouduser = re_compile('Please login as the user "({0})"'.format(user_re))
event = Event()
def loop(self):
cmd = ssh + [
'{0}@{1}'.format(self.user, self.args.host),
inner_cmd,
]
with open(devnull, 'w') as drop:
log.debug('executing: ' + ' '.join(cmd))
self.child = Popen(cmd, stdout=PIPE, stderr=drop)
(stdout, _) = self.child.communicate()
exp = (expected_output + '\n').encode('ascii')
if self.child.returncode == 0 and stdout == exp:
if self.args.print_user:
print(self.user)
return True
if self.args.cloud_user:
match = self.re_clouduser.search(str(stdout))
if match:
self.user = match.group(1)
log.info('cloud user switched to ' + self.user)
return False
def run(self):
while True:
if self.loop():
# Success!
break
if self.event.wait(1):
log.debug("stopping per kill event")
break
def kill(self):
self.event.set()
# Best effort kill.
try:
self.child.kill()
except:
pass
self.join()
parser = ArgumentParser(
description="Wait till the host's ssh becomes responsive.")
parser.add_argument('host', help='hostname or IP')
parser.add_argument('--timeout',
help='seconds to wait before failure, default=indefinitely',
default=None, type=float)
parser.add_argument('--check-cloud-user', action='store_true', default=False,
dest='cloud_user',
help='if cloud-init disallows "root" login, try to detect the cloud ' \
+'user and use that')
parser.add_argument('--print-user', action='store_true', default=False,
dest='print_user',
help='print the username which succeeded to connect on stdout')
parser.add_argument('--log', default=False,
dest='log_verbosity',
help='set the threshold for logging, e.g. debug, info, error, ...')
def main():
sleep_period = 1.0
args = parser.parse_args()
if args.log_verbosity:
log.setLevel(logging.getLevelName(args.log_verbosity.upper()))
def timeouted():
if args.timeout is None:
return False
log.debug("wait {0}s, remains {1}s".format(sleep_period, args.timeout))
args.timeout -= sleep_period
return args.timeout <= 0
checker = Checker()
checker.args = args
checker.start()
try:
# threading.join() is not Ctrl-C interruptable :( in python2, so we need
# this ugly infinite loop.
# https://stackoverflow.com/questions/25676835/signal-handling-in-multi-threaded-python
while True:
checker.join(sleep_period)
if not checker.is_alive():
# Success!
return 0
if timeouted():
log.error("timeout!")
checker.kill()
return 1
except KeyboardInterrupt:
log.error("interrupt by user")
checker.kill()
return 1
if __name__ == "__main__":
sys.exit(main())
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