基于ceph的cinder backup功能代码分析
1、cinder/backup/api.py 239 create687
def create(self, context, name, description, volume_id,
container, incremental=False, availability_zone=None,
force=False, snapshot_id=None):检查磁盘状态，磁盘快照以及快照状态以及in-use时是否加了force，检查backup配额,由于我们使用的是ceph的driver，获取dirver的过程就不看了主要看看实现的地方
2、cinder/backup/drivers/ceph.py 840 backup函数
def backup(self, backup, volume_file, backup_metadata=True):
"""Backup volume and metadata (if available) to Ceph object store.
If the source volume is an RBD we will attempt to do an
incremental/differential backup, otherwise a full copy is performed.
If this fails we will attempt to fall back to full copy.
"""
backup_id = backup['id']
volume = self.db.volume_get(self.context, backup['volume_id'])
volume_id = volume['id']
volume_name = volume['name']
LOG.debug("Starting backup of volume='%s'.", volume_id)
# Ensure we are at the beginning of the volume
volume_file.seek(0)
length = self._get_volume_size_gb(volume)
do_full_backup = False
if self._file_is_rbd(volume_file):
# If volume an RBD, attempt incremental backup.
try:
self._backup_rbd(backup_id, volume_id, volume_file,
volume_name, length)
except exception.BackupRBDOperationFailed:
LOG.debug("Forcing full backup of volume %s.", volume_id)
do_full_backup = True
else:
do_full_backup = True
if do_full_backup:
self._full_backup(backup_id, volume_id, volume_file,
volume_name, length)
backup.container = self._ceph_backup_pool
backup.save()
if backup_metadata:
try:
self._backup_metadata(backup)
except exception.BackupOperationError:
with excutils.save_and_reraise_exception():
# Cleanup.
self.delete(backup)
LOG.debug("Backup '%(backup_id)s' of volume %(volume_id)s finished.",
{'backup_id': backup_id, 'volume_id': volume_id})3、cinder/backup/drivers/ceph.py 589 _backup_rbd函数
def _backup_rbd(self, backup_id, volume_id, volume_file, volume_name,
length):
"""Create an incremental backup from an RBD image."""
rbd_user = volume_file.rbd_user
rbd_pool = volume_file.rbd_pool
rbd_conf = volume_file.rbd_conf
source_rbd_image = volume_file.rbd_image
# Identify our --from-snap point (if one exists)
from_snap = self._get_most_recent_snap(source_rbd_image)
LOG.debug("Using --from-snap '%(snap)s' for incremental backup of "
"volume %(volume)s.",
{'snap': from_snap, 'volume': volume_id})
base_name = self._get_backup_base_name(volume_id, diff_format=True)
image_created = False
with rbd_driver.RADOSClient(self, self._ceph_backup_pool) as client:
# If from_snap does not exist at the destination (and the
# destination exists), this implies a previous backup has failed.
# In this case we will force a full backup.
#
# TODO(dosaboy): find a way to repair the broken backup
#
if base_name not in self.rbd.RBD().list(ioctx=client.ioctx):
# If a from_snap is defined but the base does not exist, we
# ignore it since it is stale and waiting to be cleaned up.
if from_snap:
LOG.debug("Source snapshot '%(snapshot)s' of volume "
"%(volume)s is stale so deleting.",
{'snapshot': from_snap, 'volume': volume_id})
source_rbd_image.remove_snap(from_snap)
from_snap = None
# Create new base image
#创建基础镜像用于后期数据拷贝过来
self._create_base_image(base_name, length, client)
image_created = True
else:
# If a from_snap is defined but does not exist in the back base
# then we cannot proceed (see above)
if not self._snap_exists(base_name, from_snap, client):
errmsg = (_("Snapshot='%(snap)s' does not exist in base "
"image='%(base)s' - aborting incremental "
"backup") %
{'snap': from_snap, 'base': base_name})
LOG.info(errmsg)
# Raise this exception so that caller can try another
# approach
raise exception.BackupRBDOperationFailed(errmsg)
# Snapshot source volume so that we have a new point-in-time
new_snap = self._get_new_snap_name(backup_id)
LOG.debug("Creating backup snapshot='%s'", new_snap)
source_rbd_image.create_snap(new_snap)
# Attempt differential backup. If this fails, perhaps because librbd
# or Ceph cluster version does not support it, do a full backup
# instead.
#
# TODO(dosaboy): find a way to determine if the operation is supported
# rather than brute force approach.
try:
before = time.time()
self._rbd_diff_transfer(volume_name, rbd_pool, base_name,
self._ceph_backup_pool,
src_user=rbd_user,
src_conf=rbd_conf,
dest_user=self._ceph_backup_user,
dest_conf=self._ceph_backup_conf,
src_snap=new_snap,
from_snap=from_snap)
LOG.debug("Differential backup transfer completed in %.4fs",
(time.time() - before))
# We don't need the previous snapshot (if there was one) anymore so
# delete it.
if from_snap:
source_rbd_image.remove_snap(from_snap)
except exception.BackupRBDOperationFailed:
with excutils.save_and_reraise_exception():
LOG.debug("Differential backup transfer failed")
# Clean up if image was created as part of this operation
if image_created:
self._try_delete_base_image(backup_id, volume_id,
base_name=base_name)
# Delete snapshot
LOG.debug("Deleting diff backup snapshot='%(snapshot)s' of "
"source volume='%(volume)s'.",
{'snapshot': new_snap, 'volume': volume_id})
source_rbd_image.remove_snap(new_snap)4、cinder/backup/drivers/ceph.py 515 _rbd_diff_transfer函数
这里才是真正干活的地方
def _rbd_diff_transfer(self, src_name, src_pool, dest_name, dest_pool,src_user, src_conf, dest_user, dest_conf,src_snap=None, from_snap=None):
"""Copy only extents changed between two points.
If no snapshot is provided, the diff extents will be all those changed
since the rbd volume/base was created, otherwise it will be those
changed since the snapshot was created.
"""
LOG.debug("Performing differential transfer from '%(src)s' to "
"'%(dest)s'",
{'src': src_name, 'dest': dest_name})
# NOTE(dosaboy): Need to be tolerant of clusters/clients that do
# not support these operations since at the time of writing they
# were very new.
src_ceph_args = self._ceph_args(src_user, src_conf, pool=src_pool)
dest_ceph_args = self._ceph_args(dest_user, dest_conf, pool=dest_pool)
cmd1 = ['rbd', 'export-diff'] + src_ceph_args
if from_snap is not None:
cmd1.extend(['--from-snap', from_snap])
if src_snap:
path = utils.convert_str("%s/%s@%s"
% (src_pool, src_name, src_snap))
else:
path = utils.convert_str("%s/%s" % (src_pool, src_name))
cmd1.extend([path, '-'])
cmd2 = ['rbd', 'import-diff'] + dest_ceph_args
rbd_path = utils.convert_str("%s/%s" % (dest_pool, dest_name))
cmd2.extend(['-', rbd_path])
ret, stderr = self._piped_execute(cmd1, cmd2)
if ret:
msg = (_("RBD diff op failed - (ret=%(ret)s stderr=%(stderr)s)") %
{'ret': ret, 'stderr': stderr})
LOG.info(msg)
raise exception.BackupRBDOperationFailed(msg)其实基于ceph后端的cinder backup最终重要的是两个三个地方：
1、对volume先做一个全量拷贝
2、对volume的拷贝做快照
rbd create voulmes/test
rbd snap create volumes/test@snap3、在快照的基础上做增量快照
导出增量部分
rbd export-diff volumes/test@snap snap1
创建一个新的镜像
rbd create backup/volume-$volume-id.backup.base
导入增量部分
rbd import-diff snap1 backup/volume-$volume-id.backup.base完成上述步骤即可完成增量导入