Re: [Qemu-devel] [PATCH 1/3] backup: QEMU Backup Tool

[Ishani]

----- On Aug 22, 2017, at 7:43 PM, stefanha address@hidden wrote:

> On Mon, Aug 21, 2017 at 04:40:37PM +0530, Ishani Chugh wrote:
>> qemu-backup will be a command-line tool for performing full and
>> incremental disk backups on running VMs. It is intended as a
>> reference implementation for management stack and backup developers
>> to see QEMU's backup features in action. The tool writes details of
>> guest in a configuration file and the data is retrieved from the file
>> while creating a backup. The location of config file can be set as an
>> environment variable QEMU_BACKUP_CONFIG. The usage is as follows:
>> 
>> Add a guest
>> python qemu-backup.py guest add --guest <guest_name> --qmp <socket_path>
>> 
>> Add a drive for backup in a specified guest
>> python qemu-backup.py drive add --guest <guest_name> --id <drive_id> 
>> [--target
>> <target_file_path>]
>> 
>> Create backup of the added drives:
>> python qemu-backup.py backup --guest <guest_name>
>> 
>> List all guest configs in configuration file:
>> python qemu-backup.py guest list
>> 
>> Restore operation
>> python qemu-backup.py restore --guest <guest-name>
>> 
>> Remove a guest
>> python qemu-backup.py guest remove --guest <guest_name>
>> 
>> Signed-off-by: Ishani Chugh <address@hidden>
>> ---
>>  contrib/backup/qemu-backup.py | 334 
>> ++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 334 insertions(+)
>>  create mode 100644 contrib/backup/qemu-backup.py
>> 
>> diff --git a/contrib/backup/qemu-backup.py b/contrib/backup/qemu-backup.py
>> new file mode 100644
>> index 0000000..08570f7
>> --- /dev/null
>> +++ b/contrib/backup/qemu-backup.py
>> @@ -0,0 +1,334 @@
>> +#!/usr/bin/python
>> +# -*- coding: utf-8 -*-
>> +#
>> +# Copyright (C) 2017 Ishani Chugh <address@hidden>
>> +#
>> +# 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, see <http://www.gnu.org/licenses/>.
>> +#
>> +
>> +"""
>> +This file is an implementation of backup tool
>> +"""
>> +from __future__ import print_function
>> +from argparse import ArgumentParser
>> +import os
>> +import errno
>> +from socket import error as socket_error
>> +try:
>> +    import configparser
>> +except ImportError:
>> +    import ConfigParser as configparser
>> +import sys
>> +sys.path.append(os.path.join(os.path.dirname(__file__), '..', '..',
>> +                             'scripts', 'qmp'))
>> +from qmp import QEMUMonitorProtocol
>> +
>> +
>> +class BackupTool(object):
>> +    """BackupTool Class"""
>> +    def __init__(self, config_file=os.path.expanduser('~') +
>> +                 '/.config/qemu/qemu-backup-config'):
>> +        if "QEMU_BACKUP_CONFIG" in os.environ:
>> +            self.config_file = os.environ["QEMU_BACKUP_CONFIG"]
>> +        else:
>> +            self.config_file = config_file
>> +            try:
>> +                if not os.path.isdir(os.path.dirname(self.config_file)):
>> +                    os.makedirs(os.path.dirname(self.config_file))
>> +            except:
>> +                print("Cannot create config directory", file=sys.stderr)
>> +                sys.exit(1)
>> +        self.config = configparser.ConfigParser()
>> +        self.config.read(self.config_file)
>> +
>> +    def write_config(self):
>> +        """
>> +        Writes configuration to ini file.
>> +        """
>> +        config_file = open(self.config_file+".tmp", 'w')
>> +        self.config.write(config_file)
>> +        config_file.flush()
>> +        os.fsync(config_file.fileno())
>> +        config_file.close()
>> +        os.rename(self.config_file+".tmp", self.config_file)
>> +
>> +    def get_socket_address(self, socket_address):
>> +        """
>> +        Return Socket address in form of string or tuple
>> +        """
>> +        if socket_address.startswith('tcp'):
>> +            return (socket_address.split(':')[1],
>> +                    int(socket_address.split(':')[2]))
>> +        return socket_address.split(':', 2)[1]
>> +
>> +    def _full_backup(self, guest_name):
>> +        """
>> +        Performs full backup of guest
>> +        """
>> +        if guest_name not in self.config.sections():
>> +            print("Cannot find specified guest", file=sys.stderr)
>> +            sys.exit(1)
>> +
>> +        self.verify_guest_running(guest_name)
>> +        connection = QEMUMonitorProtocol(
>> +                                         self.get_socket_address(
>> +                                             
>> self.config[guest_name]['qmp']))
>> +        connection.connect()
>> +        cmd = {"execute": "transaction", "arguments": {"actions": []}}
>> +        drive_list = []
>> +        for key in self.config[guest_name]:
>> +            if key.startswith("drive_"):
>> +                drive = key[len('drive_'):]
>> +                drive_list.append(drive)
>> +                target = self.config[guest_name][key]
>> +                sub_cmd = {"type": "drive-backup", "data": {"device": drive,
>> +                                                            "target": 
>> target,
>> +                                                            "sync": "full"}}
>> +                cmd['arguments']['actions'].append(sub_cmd)
>> +        qmp_return = connection.cmd_obj(cmd)
>> +        if 'error' in qmp_return:
>> +            print(qmp_return['error']['desc'], file=sys.stderr)
>> +            sys.exit(1)
>> +        print("Backup Started")
>> +        while len(drive_list) != 0:
>> +            event = connection.pull_event(wait=True)
>> +            if event['event'] == 'SHUTDOWN':
>> +                print("The guest was SHUT DOWN", file=sys.stderr)
>> +                sys.exit(1)
>> +
>> +            if event['event'] == 'RESET':
>> +                print("The guest was Rebooted", file=sys.stderr)
>> +                sys.exit(1)
>> +
>> +            if event['data']['device'] in drive_list and \
>> +                    event['data']['type'] == 'backup':
> 
> At this point the event[] dict might be a non-BLOCK_JOB_* event.
> Therefore event['data']['device'] will raise a KeyError exception.
> 
> You must check event['event'] before assuming it contains certain
> fields.

Agreed. Will fix in next revision.
 
>> +                if event['event'] == 'BLOCK_JOB_COMPLETED':
>> +                    print("*"+event['data']['device'])
>> +                    drive_list.remove(event['data']['device'])
>> +                elif event['event'] == 'BLOCK_JOB_ERROR':
>> +                    print("Cannot Complete Backup", file=sys.stderr)
>> +                    sys.exit(1)
>> +        print("Backup Complete")
>> +
>> +    def _drive_add(self, drive_id, guest_name, target=None):
>> +        """
>> +        Adds drive for backup
>> +        """
>> +        if target is None:
>> +            target = os.path.abspath(drive_id)
>> +
>> +        if os.path.isdir(os.path.dirname(target)) is False:
>> +            print("Cannot find target directory", file=sys.stderr)
>> +            sys.exit(1)
>> +
>> +        if guest_name not in self.config.sections():
>> +            print("Cannot find specified guest", file=sys.stderr)
>> +            sys.exit(1)
>> +
>> +        if "drive_"+drive_id in self.config[guest_name]:
>> +            print("Drive already marked for backup", file=sys.stderr)
>> +            sys.exit(1)
>> +
>> +        self.verify_guest_running(guest_name)
>> +
>> +        connection = QEMUMonitorProtocol(
>> +                                         self.get_socket_address(
>> +                                             
>> self.config[guest_name]['qmp']))
>> +        connection.connect()
>> +        cmd = {'execute': 'query-block'}
>> +        returned_json = connection.cmd_obj(cmd)
>> +        device_present = False
>> +        for device in returned_json['return']:
>> +            if device['device'] == drive_id:
>> +                device_present = True
>> +                break
>> +
>> +        if not device_present:
>> +            print("No such drive in guest", file=sys.stderr)
>> +            sys.exit(1)
>> +
>> +        drive_id = "drive_" + drive_id
>> +        for d_id in self.config[guest_name]:
>> +            if self.config[guest_name][d_id] == target:
>> +                print("Please choose different target", file=sys.stderr)
>> +                sys.exit(1)
>> +        self.config.set(guest_name, drive_id, target)
>> +        self.write_config()
>> +        print("Successfully Added Drive")
>> +
>> +    def verify_guest_running(self, guest_name):
>> +        """
>> +        Checks whether specified guest is running or not
>> +        """
>> +        socket_address = self.config.get(guest_name, 'qmp')
>> +        try:
>> +            connection = QEMUMonitorProtocol(self.get_socket_address(
>> +                                             socket_address))
>> +            connection.connect()
>> +        except socket_error:
>> +            if socket_error.errno != errno.ECONNREFUSED:
>> +                print("Connection to guest refused", file=sys.stderr)
>> +                sys.exit(1)
>> +
>> +    def _guest_add(self, guest_name, socket_address):
>> +        """
>> +        Adds a guest to the config file
>> +        """
>> +        if guest_name in self.config.sections():
>> +            print("ID already exists. Please choose a different guestname",
>> +                  file=sys.stderr)
>> +            sys.exit(1)
>> +        self.config[guest_name] = {'qmp': socket_address}
>> +        self.verify_guest_running(guest_name)
>> +        self.write_config()
>> +        print("Successfully Added Guest")
>> +
>> +    def _guest_remove(self, guest_name):
>> +        """
>> +        Removes a guest from config file
>> +        """
>> +        if guest_name not in self.config.sections():
>> +            print("Guest Not present", file=sys.stderr)
>> +            sys.exit(1)
>> +        self.config.remove_section(guest_name)
>> +        print("Guest successfully deleted")
>> +
>> +    def _restore(self, guest_name):
>> +        """
>> +        Prints Steps to perform restore operation
>> +        """
>> +        if guest_name not in self.config.sections():
>> +            print("Cannot find specified guest", file=sys.stderr)
>> +            sys.exit(1)
>> +
>> +        self.verify_guest_running(guest_name)
>> +        connection = QEMUMonitorProtocol(
>> +                                         self.get_socket_address(
>> +                                             
>> self.config[guest_name]['qmp']))
>> +        connection.connect()
>> +        print("To perform restore, replace:")
>> +        for key in self.config[guest_name]:
>> +            if key.startswith("drive_"):
>> +                drive = key[len('drive_'):]
>> +                target = self.config[guest_name][key]
>> +                cmd = {'execute': 'query-block'}
>> +                returned_json = connection.cmd_obj(cmd)
>> +                device_present = False
>> +                for device in returned_json['return']:
>> +                    if device['device'] == drive:
>> +                        device_present = True
>> +                        location = device['inserted']['image']['filename']
>> +                        print(location+" By "+target)
> 
> I suggest print('Replace ' + location + ' with ' + target) for a
> slightly clearer message.

Will fix in next revision.

>> +
>> +                if not device_present:
>> +                    print("No such drive in guest", file=sys.stderr)
>> +                    sys.exit(1)
> 
> Since the command itself requires the guest to be running
> users are very likely to manipulate the disk image files while the guest
> is running.
> 
> This command must prompt the user to shut down the guest before
> restoring.

The intention behind this condition is the case where user may have detached
a disk from the guest(and have rerun the guest). I will put up the message to
shut down the guest. 

>> +
>> +    def guest_remove_wrapper(self, args):
>> +        """
>> +        Wrapper for _guest_remove method.
>> +        """
>> +        guest_name = args.guest
>> +        self._guest_remove(guest_name)
>> +        self.write_config()
>> +
>> +    def list(self, args):
>> +        """
>> +        Prints guests present in Config file
>> +        """
>> +        for guest_name in self.config.sections():
>> +            print(guest_name)
>> +
>> +    def guest_add_wrapper(self, args):
>> +        """
>> +        Wrapper for _quest_add method
>> +        """
>> +        self._guest_add(args.guest, args.qmp)
>> +
>> +    def drive_add_wrapper(self, args):
>> +        """
>> +        Wrapper for _drive_add method
>> +        """
>> +        self._drive_add(args.id, args.guest, args.target)
>> +
>> +    def fullbackup_wrapper(self, args):
>> +        """
>> +        Wrapper for _full_backup method
>> +        """
>> +        self._full_backup(args.guest)
>> +
>> +    def restore_wrapper(self, args):
>> +        """
>> +        Wrapper for restore
>> +        """
>> +        self._restore(args.guest)
>> +
>> +
>> +def main():
>> +    backup_tool = BackupTool()
>> +    parser = ArgumentParser()
>> +    subparsers = parser.add_subparsers(title='Subcommands',
>> +                                       description='Valid Subcommands',
>> +                                       help='Subcommand help')
>> +    guest_parser = subparsers.add_parser('guest', help='Adds or \
>> +                                                   removes and lists 
>> guest(s)')
>> +    guest_subparsers = guest_parser.add_subparsers(title='Guest Subparser')
>> +    guest_list_parser = guest_subparsers.add_parser('list',
>> +                                                    help='Lists all guests')
>> +    guest_list_parser.set_defaults(func=backup_tool.list)
>> +
>> +    guest_add_parser = guest_subparsers.add_parser('add', help='Adds a 
>> guest')
>> +    guest_add_parser.add_argument('--guest', action='store', type=str,
>> +                                  help='Name of the guest')
>> +    guest_add_parser.add_argument('--qmp', action='store', type=str,
>> +                                  help='Path of socket')
>> +    guest_add_parser.set_defaults(func=backup_tool.guest_add_wrapper)
>> +
>> +    guest_remove_parser = guest_subparsers.add_parser('remove',
>> +                                                      help='removes a 
>> guest')
>> +    guest_remove_parser.add_argument('--guest', action='store', type=str,
>> +                                     help='Name of the guest')
>> +    guest_remove_parser.set_defaults(func=backup_tool.guest_remove_wrapper)
>> +
>> +    drive_parser = subparsers.add_parser('drive',
>> +                                         help='Adds drive(s) for backup')
>> +    drive_subparsers = drive_parser.add_subparsers(title='Add subparser',
>> +                                                   description='Drive \
>> +                                                                subparser')
>> +    drive_add_parser = drive_subparsers.add_parser('add',
>> +                                                   help='Adds new \
>> +                                                         drive for backup')
>> +    drive_add_parser.add_argument('--guest', action='store',
>> +                                  type=str, help='Name of the guest')
>> +    drive_add_parser.add_argument('--id', action='store',
>> +                                  type=str, help='Drive ID')
>> +    drive_add_parser.add_argument('--target', nargs='?',
>> +                                  default=None, help='Destination path')
>> +    drive_add_parser.set_defaults(func=backup_tool.drive_add_wrapper)
>> +
>> +    backup_parser = subparsers.add_parser('backup', help='Creates backup')
>> +    backup_parser.add_argument('--guest', action='store',
>> +                               type=str, help='Name of the guest')
>> +    backup_parser.set_defaults(func=backup_tool.fullbackup_wrapper)
>> +
>> +    backup_parser = subparsers.add_parser('restore', help='Restores drives')
>> +    backup_parser.add_argument('--guest', action='store',
>> +                               type=str, help='Name of the guest')
>> +    backup_parser.set_defaults(func=backup_tool.restore_wrapper)
>> +
>> +    args = parser.parse_args()
>> +    args.func(args)
>> +
>> +if __name__ == '__main__':
>> +    main()
>> --
>> 2.7.4

Thanks for review.