Implement snapshots for raw backend

blueprint snapshots-for-everyone

Use simple qemu-img convert for raw snapshots.
Polymorphically select snapshot behavior for
raw and qcow2.
Allow images to be constructed from actual device/file path.

Change-Id: I6a57e43c6775c144c41a53382dcc7504ce6d4c43

4 files changed, 176 insertions, 26 deletions

diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py
index 50227ae6d..763a98e80 100644
--- a/nova/virt/libvirt/driver.py
+++ b/nova/virt/libvirt/driver.py
@@ -813,6 +813,10 @@ class LibvirtDriver(driver.ComputeDriver):
 
         image_format = FLAGS.snapshot_image_format or source_format
 
+        # NOTE(bfilippov): save lvm as raw
+        if image_format == 'lvm':
+            image_format = 'raw'
+
         # NOTE(vish): glance forces ami disk format to be ami
         if base.get('disk_format') == 'ami':
             metadata['disk_format'] = 'ami'
@@ -828,8 +832,12 @@ class LibvirtDriver(driver.ComputeDriver):
 
         if state == power_state.RUNNING:
             virt_dom.managedSave(0)
+
         # Make the snapshot
-        libvirt_utils.create_snapshot(disk_path, snapshot_name)
+        snapshot = self.image_backend.snapshot(disk_path, snapshot_name,
+                                               image_type=source_format)
+
+        snapshot.create()
 
         # Export the snapshot to a raw image
         snapshot_directory = FLAGS.libvirt_snapshots_directory
@@ -837,11 +845,9 @@ class LibvirtDriver(driver.ComputeDriver):
         with utils.tempdir(dir=snapshot_directory) as tmpdir:
             try:
                 out_path = os.path.join(tmpdir, snapshot_name)
-                libvirt_utils.extract_snapshot(disk_path, source_format,
-                                               snapshot_name, out_path,
-                                               image_format)
+                snapshot.extract(out_path, image_format)
             finally:
-                libvirt_utils.delete_snapshot(disk_path, snapshot_name)
+                snapshot.delete()
                 if state == power_state.RUNNING:
                     self._create_domain(domain=virt_dom)
 
diff --git a/nova/virt/libvirt/imagebackend.py b/nova/virt/libvirt/imagebackend.py
index 0f2f044d7..040884e17 100644
--- a/nova/virt/libvirt/imagebackend.py
+++ b/nova/virt/libvirt/imagebackend.py
@@ -25,6 +25,7 @@ from nova.openstack.common import excutils
 from nova import utils
 from nova.virt.disk import api as disk
 from nova.virt.libvirt import config
+from nova.virt.libvirt import snapshots
 from nova.virt.libvirt import utils as libvirt_utils
 
 __imagebackend_opts = [
@@ -125,13 +126,21 @@ class Image(object):
             self.create_image(call_if_not_exists, base, size,
                               *args, **kwargs)
 
+    @abc.abstractmethod
+    def snapshot(self, name):
+        """Create snapshot object for this image
+
+        :name: snapshot name
+        """
+        pass
+
 
 class Raw(Image):
-    def __init__(self, instance, name):
+    def __init__(self, instance=None, name=None, path=None):
         super(Raw, self).__init__("file", "raw", is_block_dev=False)
 
-        self.path = os.path.join(FLAGS.instances_path,
-                                 instance, name)
+        self.path = path or os.path.join(FLAGS.instances_path,
+                                         instance, name)
 
     def create_image(self, prepare_template, base, size, *args, **kwargs):
         @utils.synchronized(base, external=True, lock_path=self.lock_path)
@@ -149,13 +158,16 @@ class Raw(Image):
             with utils.remove_path_on_error(self.path):
                 copy_raw_image(base, self.path, size)
 
+    def snapshot(self, name):
+        return snapshots.RawSnapshot(self.path, name)
+
 
 class Qcow2(Image):
-    def __init__(self, instance, name):
+    def __init__(self, instance=None, name=None, path=None):
         super(Qcow2, self).__init__("file", "qcow2", is_block_dev=False)
 
-        self.path = os.path.join(FLAGS.instances_path,
-                                 instance, name)
+        self.path = path or os.path.join(FLAGS.instances_path,
+                                         instance, name)
 
     def create_image(self, prepare_template, base, size, *args, **kwargs):
         @utils.synchronized(base, external=True, lock_path=self.lock_path)
@@ -174,23 +186,33 @@ class Qcow2(Image):
         with utils.remove_path_on_error(self.path):
             copy_qcow2_image(base, self.path, size)
 
+    def snapshot(self, name):
+        return snapshots.Qcow2Snapshot(self.path, name)
+
 
 class Lvm(Image):
     @staticmethod
     def escape(filename):
         return filename.replace('_', '__')
 
-    def __init__(self, instance, name):
+    def __init__(self, instance=None, name=None, path=None):
         super(Lvm, self).__init__("block", "raw", is_block_dev=True)
 
-        if not FLAGS.libvirt_images_volume_group:
-            raise RuntimeError(_('You should specify'
-                               ' libvirt_images_volume_group'
-                               ' flag to use LVM images.'))
-        self.vg = FLAGS.libvirt_images_volume_group
-        self.lv = '%s_%s' % (self.escape(instance),
-                             self.escape(name))
-        self.path = os.path.join('/dev', self.vg, self.lv)
+        if path:
+            info = libvirt_utils.logical_volume_info(path)
+            self.vg = info['VG']
+            self.lv = info['LV']
+            self.path = path
+        else:
+            if not FLAGS.libvirt_images_volume_group:
+                raise RuntimeError(_('You should specify'
+                                     ' libvirt_images_volume_group'
+                                     ' flag to use LVM images.'))
+            self.vg = FLAGS.libvirt_images_volume_group
+            self.lv = '%s_%s' % (self.escape(instance),
+                                 self.escape(name))
+            self.path = os.path.join('/dev', self.vg, self.lv)
+
         self.sparse = FLAGS.libvirt_sparse_logical_volumes
 
     def create_image(self, prepare_template, base, size, *args, **kwargs):
@@ -227,6 +249,9 @@ class Lvm(Image):
             with excutils.save_and_reraise_exception():
                 libvirt_utils.remove_logical_volumes(path)
 
+    def snapshot(self, name):
+        return snapshots.LvmSnapshot(self.path, name)
+
 
 class Backend(object):
     def __init__(self, use_cow):
@@ -237,6 +262,14 @@ class Backend(object):
             'default': Qcow2 if use_cow else Raw
         }
 
+    def backend(self, image_type=None):
+        if not image_type:
+            image_type = FLAGS.libvirt_images_type
+        image = self.BACKEND.get(image_type)
+        if not image:
+            raise RuntimeError(_('Unknown image_type=%s') % image_type)
+        return image
+
     def image(self, instance, name, image_type=None):
         """Constructs image for selected backend
 
@@ -245,9 +278,15 @@ class Backend(object):
         :image_type: Image type.
         Optional, is FLAGS.libvirt_images_type by default.
         """
-        if not image_type:
-            image_type = FLAGS.libvirt_images_type
-        image = self.BACKEND.get(image_type)
-        if not image:
-            raise RuntimeError(_('Unknown image_type=%s') % image_type)
-        return image(instance, name)
+        backend = self.backend(image_type)
+        return backend(instance=instance, name=name)
+
+    def snapshot(self, path, snapshot_name, image_type=None):
+        """Returns snapshot for given image
+
+        :path: path to image
+        :snapshot_name: snapshot name
+        :image_type: type of image
+        """
+        backend = self.backend(image_type)
+        return backend(path=path).snapshot(snapshot_name)
diff --git a/nova/virt/libvirt/snapshots.py b/nova/virt/libvirt/snapshots.py
new file mode 100644
index 000000000..37933876d
--- /dev/null
+++ b/nova/virt/libvirt/snapshots.py
@@ -0,0 +1,89 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2012 Grid Dynamics
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import abc
+
+from nova.virt import images
+from nova.virt.libvirt import utils as libvirt_utils
+
+
+class Snapshot(object):
+    @abc.abstractmethod
+    def create(self):
+        """Create new snapshot"""
+        pass
+
+    @abc.abstractmethod
+    def extract(self, target, out_format):
+        """Extract snapshot content to file
+
+        :target: path to extraction
+        :out_format: format of extraction (raw, qcow2, ...)
+        """
+        pass
+
+    @abc.abstractmethod
+    def delete(self):
+        """Delete snapshot"""
+        pass
+
+
+class RawSnapshot(object):
+    def __init__(self, path, name):
+        self.path = path
+        self.name = name
+
+    def create(self):
+        pass
+
+    def extract(self, target, out_format):
+        images.convert_image(self.path, target, out_format)
+
+    def delete(self):
+        pass
+
+
+class Qcow2Snapshot(object):
+    def __init__(self, path, name):
+        self.path = path
+        self.name = name
+
+    def create(self):
+        libvirt_utils.create_snapshot(self.path, self.name)
+
+    def extract(self, target, out_format):
+        libvirt_utils.extract_snapshot(self.path, 'qcow2',
+                                       self.name, target,
+                                       out_format)
+
+    def delete(self):
+        libvirt_utils.delete_snapshot(self.path, self.name)
+
+
+class LvmSnapshot(object):
+    def __init__(self, path, name):
+        self.path = path
+        self.name = name
+
+    def create(self):
+        raise NotImplementedError(_("LVM snapshots not implemented"))
+
+    def extract(self, target, out_format):
+        raise NotImplementedError(_("LVM snapshots not implemented"))
+
+    def delete(self):
+        raise NotImplementedError(_("LVM snapshots not implemented"))
diff --git a/nova/virt/libvirt/utils.py b/nova/virt/libvirt/utils.py
index 2d1b5558c..17c9efdda 100644
--- a/nova/virt/libvirt/utils.py
+++ b/nova/virt/libvirt/utils.py
@@ -172,6 +172,22 @@ def list_logical_volumes(vg):
     return [line.strip() for line in out.splitlines()]
 
 
+def logical_volume_info(path):
+    """Get logical volume info.
+
+    :param path: logical volume path
+    """
+    out, err = execute('lvs', '-o', 'vg_all,lv_all',
+                       '--separator', '|', path, run_as_root=True)
+
+    info = [line.split('|') for line in out.splitlines()]
+
+    if len(info) != 2:
+        raise RuntimeError(_("Path %s must be LVM logical volume") % path)
+
+    return dict(zip(*info))
+
+
 def remove_logical_volumes(*paths):
     """Remove one or more logical volume."""
     if paths: