Refactor libvirt imagebackend module to reduce code duplication

Currently each subclass of the Image class in imagebackend,
repeats the impl of the 'libvirt_info' method. These methods
are almost identical, only varying on two per-class settings.
By providing the driver_format and source_type to the Image
class constructor, it is possible to get to a single impl
of the 'libvirt_info' method.

Change-Id: I0807eed7f03aedf4980eedeb70195076ed5f4710
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

1 files changed, 24 insertions, 40 deletions

diff --git a/nova/virt/libvirt/imagebackend.py b/nova/virt/libvirt/imagebackend.py
index 7140e6527..bc0489fbd 100644
--- a/nova/virt/libvirt/imagebackend.py
+++ b/nova/virt/libvirt/imagebackend.py
@@ -50,14 +50,14 @@ FLAGS.register_opts(__imagebackend_opts)
 class Image(object):
     __metaclass__ = abc.ABCMeta
 
-    @abc.abstractmethod
-    def __init__(self, instance, name):
+    def __init__(self, source_type, driver_format):
         """Image initialization.
 
-        :instance: Instance name.
-        :name: Image name.
+        :source_type: block or file
+        :driver_format: raw or qcow2
         """
-        pass
+        self.source_type = source_type
+        self.driver_format = driver_format
 
     @abc.abstractmethod
     def create_image(self, prepare_template, base, size, *args, **kwargs):
@@ -72,7 +72,6 @@ class Image(object):
         """
         pass
 
-    @abc.abstractmethod
     def libvirt_info(self, disk_bus, disk_dev, device_type, cache_mode):
         """Get `LibvirtConfigGuestDisk` filled for this image.
 
@@ -81,7 +80,15 @@ class Image(object):
         :device_type: Device type for this image.
         :cache_mode: Caching mode for this image
         """
-        pass
+        info = config.LibvirtConfigGuestDisk()
+        info.source_type = self.source_type
+        info.source_device = device_type
+        info.target_bus = disk_bus
+        info.target_dev = disk_dev
+        info.driver_cache = cache_mode
+        info.driver_format = self.driver_format
+        info.source_path = self.path
+        return info
 
     def cache(self, fn, fname, size=None, *args, **kwargs):
         """Creates image from template.
@@ -112,20 +119,11 @@ class Image(object):
 
 class Raw(Image):
     def __init__(self, instance, name):
+        super(Raw, self).__init__("file", "raw")
+
         self.path = os.path.join(FLAGS.instances_path,
                                  instance, name)
 
-    def libvirt_info(self, disk_bus, disk_dev, device_type, cache_mode):
-        info = config.LibvirtConfigGuestDisk()
-        info.source_type = 'file'
-        info.source_device = device_type
-        info.target_bus = disk_bus
-        info.target_dev = disk_dev
-        info.driver_cache = cache_mode
-        info.driver_format = 'raw'
-        info.source_path = self.path
-        return info
-
     def create_image(self, prepare_template, base, size, *args, **kwargs):
         @utils.synchronized(base)
         def copy_raw_image(base, target, size):
@@ -143,17 +141,12 @@ class Raw(Image):
                 copy_raw_image(base, self.path, size)
 
 
-class Qcow2(Raw):
-    def libvirt_info(self, disk_bus, disk_dev, device_type, cache_mode):
-        info = config.LibvirtConfigGuestDisk()
-        info.source_type = 'file'
-        info.source_device = device_type
-        info.target_bus = disk_bus
-        info.target_dev = disk_dev
-        info.driver_cache = cache_mode
-        info.driver_format = 'qcow2'
-        info.source_path = self.path
-        return info
+class Qcow2(Image):
+    def __init__(self, instance, name):
+        super(Qcow2, self).__init__("file", "qcow2")
+
+        self.path = os.path.join(FLAGS.instances_path,
+                                 instance, name)
 
     def create_image(self, prepare_template, base, size, *args, **kwargs):
         @utils.synchronized(base)
@@ -178,18 +171,9 @@ class Lvm(Image):
     def escape(fname):
         return fname.replace('_', '__')
 
-    def libvirt_info(self, disk_bus, disk_dev, device_type, cache_mode):
-        info = config.LibvirtConfigGuestDisk()
-        info.source_type = 'block'
-        info.source_device = device_type
-        info.target_bus = disk_bus
-        info.target_dev = disk_dev
-        info.driver_cache = cache_mode
-        info.driver_format = 'raw'
-        info.source_path = self.path
-        return info
-
     def __init__(self, instance, name):
+        super(Lvm, self).__init__("block", "raw")
+
         if not FLAGS.libvirt_images_volume_group:
             raise RuntimeError(_('You should specify'
                                ' libvirt_images_volume_group'