Mini Shell

#!/opt/cloudlinux/venv/bin/python3 -bb
# coding: utf-8

# Copyright © Cloud Linux GmbH & Cloud Linux Software, Inc 2010-2018 All Rights Reserved
#
# Licensed under CLOUD LINUX LICENSE AGREEMENT
# http://cloudlinux.com/docs/LICENSE.TXT
import fcntl
import sys
import time

import os
from argparse import ArgumentParser
from clcommon.sysctl import SysCtlConf, SysCtlMigrate, SYSCTL_CL_CONF_FILE, SYSCTL_FILE

SELF_LOCK_FILE = '/var/log/cl_sysctl.lock'


def create_parser():
    config_help = 'Path to sysctl config file. It\'s %(default)s by default'
    config_path = SYSCTL_CL_CONF_FILE

    parser = ArgumentParser(description='Utility for working with sysctl configs. INTERNAL USAGE ONLY!')
    subparsers = parser.add_subparsers(dest='command')

    subparser_set = subparsers.add_parser(name='set', help='Set or add the the sysctl parameter to the sysctl config')
    subparser_set.add_argument('-P', '--parameter', action='store', required=True,
                               help='Name of the sysctl parameter')
    subparser_set.add_argument('-V', '--value', action='store', required=True,
                               help='Value of the sysctl parameter')
    subparser_set.add_argument('-C', '--config', action='store',
                               help=config_help,
                               default=config_path)

    subparser_get = subparsers.add_parser(name='get', help='Get the sysctl parameter')
    subparser_get.add_argument('-P', '--parameter', action='store', required=True,
                               help='Name of the sysctl parameter')
    subparser_get.add_argument('-C', '--config', action='store',
                               help=config_help,
                               default=config_path)

    subparser_remove = subparsers.add_parser(name='remove', help='Remove the sysctl parameter from the sysctl config')
    subparser_remove.add_argument('-P', '--parameter', action='store', required=True,
                                  help='Name of the sysctl parameter')
    subparser_remove.add_argument('-C', '--config', action='store',
                                  help=config_help,
                                  default=config_path)

    subparsers_migrate = subparsers.add_parser(name='migrate',
                                               help='Migrate sysctl param from {} to {}'.format(
                                                   SYSCTL_FILE,
                                                   SYSCTL_CL_CONF_FILE,
                                               ))
    subparsers_migrate.add_argument('-P', '--parameter', action='store', required=True,
                                    help='Name of the sysctl parameter')
    subparsers_migrate.add_argument('-dV', '--default-value', action='store',
                                    help='Default value of sysctl parameter if it is absent in source file')

    return parser


def _parse_args(argv):
    parser = create_parser()
    params = parser.parse_args(argv)
    return params


def main_(args):
    params = _parse_args(args)
    command = params.command
    if command == 'set':
        config_file = params.config
        sysctl = SysCtlConf(config_file=config_file)
        sysctl.set(name=params.parameter,
                   value=params.value)
    elif command == 'get':
        config_file = params.config
        sysctl = SysCtlConf(config_file=config_file)
        value = sysctl.get(name=params.parameter)
        print(value)
    elif command == 'remove':
        config_file = params.config
        sysctl = SysCtlConf(config_file=config_file)
        sysctl.remove(name=params.parameter)
    elif command == 'migrate':
        sysctl_migrate = SysCtlMigrate()
        sysctl_migrate.migrate(
            param_name=params.parameter,
            default_value=params.default_value,
        )


def main():
    with open(SELF_LOCK_FILE, 'w') as lock_file:
        lock_file_is_locked = True
        for _ in range(20):
            try:
                fcntl.flock(lock_file, fcntl.LOCK_EX | fcntl.LOCK_NB)
                lock_file_is_locked = False
                break
            except IOError:
                print('Another app is currently holding the cl_sysctl lock; waiting for it to exit.')
                time.sleep(5)
        if lock_file_is_locked:
            print('Another app is still holding the cl_sysctl lock after 20 attempts. Please, try again later.')
            exit(1)
        else:
            main_(sys.argv[1:])
    try:
        os.remove(SELF_LOCK_FILE)
    except (IOError, OSError):
        pass


if __name__ == '__main__':
    main()