Python version of toollabs remote crontab
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Authored by zhuyifei1999 on Feb 9 2017, 2:41 PM.

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	F5571113: Python version of toollabs remote crontab
	Feb 9 2017, 2:41 PM

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	#! /usr/bin/python -Es
	# -- coding: UTF-8 --
	#
	# Copyright © 2013 Marc-André Pelletier <mpelletier@wikimedia.org>
	# Copyright © 2017 Zhuyifei1999 <zhuyifei1999@gmail.com>
	#
	# Permission to use, copy, modify, and/or distribute this software for any
	# purpose with or without fee is hereby granted, provided that the above
	# copyright notice and this permission notice appear in all copies.
	#
	# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
	# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
	#

	# This goes in /usr/local/bin to override the system crontab (which will
	# have its permissions restricted).

	# THIS FILE IS MANAGED BY PUPPET
	#
	# This goes in /usr/local/bin to override the system crontab (which will
	# have its permissions restricted).
	#
	# Source: modules/toollabs/templates/crontab.erb
	# From: toollabs::submit

	from __future__ import print_function

	import argparse
	import pwd
	import os
	import re
	import subprocess
	import sys
	import tempfile

	# TODO: read from somewhere like /etc/toollabs-cronhost
	CRON_HOST = 'tools-cron-01.tools.eqiad.wmflabs' # FIXME: <%= @cron_host %>
	JSUB_MODIFIED = '''
	NOTE: some crontab entries have been modified to grid submissions.
	You may want to examine the result with 'crontab -e'.
	'''
	DEFAULT_CRONTAB = '''\
	# Edit this file to introduce tasks to be run by cron.
	#
	# Each task to run has to be defined through a single line
	# indicating with different fields when the task will be run
	# and what command to run for the task
	#
	# To define the time you can provide concrete values for
	# minute (m), hour (h), day of month (dom), month (mon),
	# and day of week (dow) or use '*' in these fields (for 'any').#
	# Notice that tasks will be started based on the cron's system
	# daemon's notion of time and timezones.
	#
	# Output of the crontab jobs (including errors) is sent through
	# email to the user the crontab file belongs to (unless redirected).
	#
	# For example, you can run a backup of all your user accounts
	# at 5 a.m every week with:
	# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
	#
	# For more information see the manual pages of crontab(5) and cron(8)
	#
	# Wikimedia Tool Labs specific note:
	# Please be aware that only jsub and jstart are acceptable
	# commands to schedule via cron. Any command specified here will
	# be modified to be invoked through jsub unless it is one of
	# the two.
	#
	# m h dom mon dow command
	'''

	parser = argparse.ArgumentParser()
	parser.add_argument('-u', help=argparse.SUPPRESS,
	dest='user')
	parser.add_argument('-i', help='prompt before deleting crontab',
	action='store_true')
	group = parser.add_mutually_exclusive_group()
	group.add_argument('file', help='replace crontab with file (default)',
	default=sys.stdin, nargs='?', type=argparse.FileType('r'))
	subgroup = group.add_mutually_exclusive_group()
	subgroup.add_argument('-e', help='edit crontab',
	action='store_const', const='e', dest='operation')
	subgroup.add_argument('-l', help='list crontab',
	action='store_const', const='l', dest='operation')
	subgroup.add_argument('-r', help='delete crontab',
	action='store_const', const='r', dest='operation')


	class NoCrontab(Exception):
	pass


	class Crontab(object):
	def __init__(self, user):
	self.user = user

	def _remote(self, args, stdin=None):
	"""Execute remote crontab command and returns stdout."""
	args = ['/usr/bin/ssh', CRON_HOST, '/usr/bin/crontab'] + args
	if self.user.pw_uid != os.getuid():
	args += ['-u', self.user.pw_name]

	ssh = subprocess.Popen(args,
	stdin=subprocess.PIPE,
	stdout=subprocess.PIPE,
	stderr=subprocess.PIPE)

	stdoutdata, stderrdata = ssh.communicate(input=stdin)

	if ssh.returncode:
	if stderrdata.lower().startswith('no crontab for '):
	raise NoCrontab
	else:
	print(stderrdata, end='', file=sys.stderr)
	err('unable to execute remote crontab command')
	sys.exit(ssh.returncode)

	return stdoutdata

	@staticmethod
	def _add_jsub(text):
	# TODO: regex insanity here
	return text

	def load(self):
	return self._remote(['-l'])

	def save(self, text):
	jsub_text = self._add_jsub(text)
	if jsub_text != text:
	print(JSUB_MODIFIED, file=sys.stderr)
	self._remote([], stdin=jsub_text)

	def remove(self):
	self._remote(['-r'])


	def editor(text):
	with tempfile.NamedTemporaryFile() as f:
	f.write(text)
	f.flush()

	subprocess.check_call(['/usr/bin/sensible-editor', f.name])

	f.seek(0)
	return f.read()


	def err(message):
	print('{}: {}'.format(sys.argv[0], message), file=sys.stderr)


	def main():
	args = parser.parse_args()

	if args.i and args.operation != 'r':
	parser.error('argument -i: only applicable with -r')

	target = pwd.getpwuid(os.getuid())
	if args.user is not None:
	if os.getuid():
	parser.error('argument -u: must be privileged')

	try:
	target = pwd.getpwnam(args.user)
	except KeyError:
	parser.error('argument -u: unknown user "{}"'.format(args.user))

	if target.pw_uid < 500:
	# If the target user is not managed in LDAP and thus likely
	# a system user, invoke the original crontab instead.
	os.execv('/usr/bin/crontab', sys.argv[1:])
	elif target.pw_uid < 40000 and os.getuid():
	err('only tools are allowed crontabs')
	sys.exit(1)
	else:
	try:
	crontab = Crontab(target)

	if args.operation is None:
	# Replace
	crontab.save(args.file.read())
	elif args.operation == 'e':
	# Edit
	try:
	crontab_text = crontab.load()
	except NoCrontab:
	crontab_text = DEFAULT_CRONTAB
	new_crontab_text = editor(crontab_text)

	if new_crontab_text == crontab_text:
	print('No modification made', file=sys.stderr)
	elif not new_crontab_text.strip():
	err('cowardly refusing to install empty crontab')
	err('use `{} -r` if you want to remove the crontab'.format(
	sys.srgv[0]))
	sys.exit(1)
	else:
	crontab.save(new_crontab_text)
	elif args.operation == 'l':
	# List
	try:
	print(crontab.load(), end='') # crontab already has lf
	except NoCrontab:
	print('no crontab for {}'.format(target.pw_name),
	file=sys.stderr)
	sys.exit(1)
	elif args.operation == 'r':
	# Delete
	try:
	crontab.load()
	except NoCrontab:
	print('no crontab for {}'.format(target.pw_name),
	file=sys.stderr)
	sys.exit(1)
	if args.i:
	prompt = "{}: really delete {}'s crontab? (y/n) ".format(
	sys.argv[0], target.pw_name)
	while True:
	try:
	stdin = raw_input(prompt).lower()
	except EOFError:
	stdin = ''
	except KeyboardInterrupt:
	print(file=sys.stderr)
	raise

	if stdin == 'y':
	crontab.remove()
	break
	elif stdin == 'n':
	break
	else:
	prompt = 'Please enter Y or N: '

	else:
	crontab.remove()
	except KeyboardInterrupt:
	pass

	if __name__ == '__main__':
	main()

Event Timeline

zhuyifei1999 created this paste.Feb 9 2017, 2:41 PM

zhuyifei1999 mentioned this in T156174: Rewrite /usr/local/bin/crontab in python; fix bugs.Feb 9 2017, 2:46 PM

Python version of toollabs remote crontabActivePublicActions

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Python version of toollabs remote crontab
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