[Qemu-devel] [PATCH 2/3] Backup Tool: Support for Incremental Backup

[Ishani Chugh <chugh.ishani@research.iiit.ac.in>]

Adds incremental backup functionality.

Signed-off-by: Ishani Chugh <chugh.ishani@research.iiit.ac.in>
---
 contrib/backup/qemu-backup.py | 101 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 99 insertions(+), 2 deletions(-)

diff --git a/contrib/backup/qemu-backup.py b/contrib/backup/qemu-backup.py
index 248ca9f..7a3077a 100644
--- a/contrib/backup/qemu-backup.py
+++ b/contrib/backup/qemu-backup.py
@@ -24,11 +24,13 @@ from __future__ import print_function
 from argparse import ArgumentParser
 import os
 import errno
+from string import Template
 from socket import error as socket_error
 try:
     import configparser
 except ImportError:
     import ConfigParser as configparser
+from configparser import NoOptionError
 import sys
 sys.path.append(os.path.join(os.path.dirname(__file__), '..', '..',
                              'scripts', 'qmp'))
@@ -41,7 +43,6 @@ class BackupTool(object):
                  '/.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:
@@ -129,6 +130,97 @@ class BackupTool(object):
                         drive_list.remove(event['data']['device'])
         print("Backup Complete")
 
+    def _inc_backup(self, guest_name):
+        """
+        Performs Incremental backup
+        """
+        if guest_name not in self.config.sections():
+            print ("Cannot find specified guest", file=sys.stderr)
+            exit(1)
+
+        self.verify_guest_running(guest_name)
+        connection = QEMUMonitorProtocol(
+                                         self.get_socket_address(
+                                             self.config[guest_name]['qmp']))
+        connection.connect()
+        backup_cmd = {"execute": "transaction",
+                      "arguments": {"actions": [], "properties":
+                                    {"completion-mode": "grouped"}}}
+        bitmap_cmd = {"execute": "transaction", "arguments": {"actions": []}}
+        for key in self.config[guest_name]:
+            if key.startswith("drive_"):
+                drive = key[len('drive_'):]
+                target = self.config.get(guest_name, key).rsplit('/', 1)[0]
+                inc_backup_pattern = Template('${drive}_inc_${N}')
+                bitmap = 'qemu_backup_'+guest_name
+                try:
+                    query_block_cmd = {'execute': 'query-block'}
+                    returned_json = connection.cmd_obj(query_block_cmd)
+                    device_present = False
+                    for device in returned_json['return']:
+                        if device['device'] == drive:
+                            device_present = True
+                            bitmap_present = False
+                            for bitmaps in device['dirty-bitmaps']:
+                                if bitmap == bitmaps['name']:
+                                    bitmap_present = True
+                                    if os.path.isfile(self.config.get(
+                                                      guest_name,
+                                                      'inc_'+drive)) is False:
+                                        print("Initial Backup does not exist")
+                                        bitmap_remove = {"execute":
+                                                         "block-dirty" +
+                                                         "-bitmap-remove",
+                                                         "arguments":
+                                                         {"node": drive,
+                                                          "name":
+                                                          "qemu_backup_" +
+                                                          guest_name}}
+                                        connection.cmd_obj(bitmap_remove)
+                                        bitmap_present = False
+                            if bitmap_present is False:
+                                raise NoOptionError(guest_name, 'inc_'+drive)
+                            break
+
+                    if not device_present:
+                        print("No such drive in guest", file=sys.stderr)
+                        sys.exit(1)
+                    N = int(self.config.get(guest_name, drive+'_N'))+1
+                    target = self.config.get(guest_name, key).rsplit(
+                                                                    '/', 1)[0]\
+                        + '/' + inc_backup_pattern.substitute(drive=drive, N=N)
+                    os.system("qemu-img create -f qcow2 " + target + " -b " +
+                              self.config.get(guest_name, 'inc_' +
+                                              drive) + " -F qcow2")
+                    sub_cmd = {"type": "drive-backup",
+                               "data": {"device": drive, "bitmap": bitmap,
+                                        "mode": "existing",
+                                        "sync": "incremental",
+                                        "target": target}}
+                    backup_cmd['arguments']['actions'].append(sub_cmd)
+                    self.config.set(guest_name, drive+'_N',
+                                    str(int(self.config.get(guest_name,
+                                                            drive+'_N'))+1))
+                    self.config.set(guest_name, 'inc_'+drive, target)
+                except (NoOptionError, KeyError) as e:
+                    target = self.config.get(guest_name, key).rsplit(
+                                                                    '/', 1)[0]\
+                        + '/' + inc_backup_pattern.substitute(drive=drive, N=0)
+                    sub_cmd_1 = {"type": "block-dirty-bitmap-add",
+                                 "data": {"node": drive, "name": bitmap,
+                                          "persistent": True,
+                                          "autoload": True}}
+                    sub_cmd_2 = {"type": "drive-backup",
+                                 "data": {"device": drive, "target": target,
+                                          "sync": "full", "format": "qcow2"}}
+                    self.config.set(guest_name, drive+'_N', '0')
+                    self.config.set(guest_name, 'inc_'+drive, target)
+                    bitmap_cmd['arguments']['actions'].append(sub_cmd_1)
+                    bitmap_cmd['arguments']['actions'].append(sub_cmd_2)
+        connection.cmd_obj(bitmap_cmd)
+        connection.cmd_obj(backup_cmd)
+        self.write_config()
+
     def _drive_add(self, drive_id, guest_name, target=None):
         """
         Adds drive for backup
@@ -275,7 +367,10 @@ class BackupTool(object):
         """
         Wrapper for _full_backup method
         """
-        self._full_backup(args.guest)
+        if args.inc is False:
+            self._full_backup(args.guest)
+        else:
+            self._inc_backup(args.guest)
 
     def restore_wrapper(self, args):
         """
@@ -329,6 +424,8 @@ def main():
     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.add_argument('--inc', nargs='?',
+                               default=False, help='Destination path')
     backup_parser.set_defaults(func=backup_tool.fullbackup_wrapper)
 
     backup_parser = subparsers.add_parser('restore', help='Restores drives')
-- 
2.7.4