libvirt: Use the mirror element to detect job completion

The mirror element was introduced in Libvirt 0.10.0 [1] and provides a
ready attribute that helps to determine when a blockjob is complete.
This is now used in addition to checking the progress of a given
blockjob to ensure Nova waits until these jobs complete fully.

[1] https://libvirt.org/git/?p=libvirt.git;a=commit;h=ae6aa8c3965e9aaa245b8e669c6324d44312ac1b

Closes-bug: #1643017
Change-Id: I0c52917a5555a70c4973f37dea1aebf878dd73b4

nova/tests/unit/virt/libvirt/test_config.py

@@ -772,6 +772,24 @@ class LibvirtConfigGuestDiskTest(LibvirtConfigBaseTest):
               <boot order="1"/>
             </disk>""", xml)
 
+    def test_config_mirror_parse(self):
+        xml = """
+<disk type="file" device="disk">
+  <driver name="qemu" type="qcow2" cache="none" discard="unmap"/>
+  <source file="/tmp/hello.qcow2"/>
+  <target bus="ide" dev="/dev/hda"/>
+  <serial>7a97c4a3-6f59-41d4-bf47-191d7f97f8e9</serial>
+  <mirror type='file' file='/tmp/new.img' format='raw' job='copy' ready='yes'>
+    <format type='raw'/>
+    <source file='/tmp/new.img'/>
+  </mirror>
+  <boot order="1"/>
+</disk>"""
+        xmldoc = etree.fromstring(xml)
+        obj = config.LibvirtConfigGuestDisk()
+        obj.parse_dom(xmldoc)
+        self.assertEqual(obj.mirror.ready, "yes")
+
     def test_config_boot_order_parse(self):
         xml = """
             <disk type="file" device="disk">

nova/tests/unit/virt/libvirt/test_guest.py

@@ -682,14 +682,32 @@ class GuestBlockTestCase(test.NoDBTestCase):
         is_complete = self.gblock.is_job_complete()
         self.assertFalse(is_complete)
 
-    def test_is_job_complete_finished(self):
-        self.domain.blockJobInfo.return_value = {
-            "type": 4,
-            "bandwidth": 18,
-            "cur": 100,
-            "end": 100}
-        is_complete = self.gblock.is_job_complete()
-        self.assertTrue(is_complete)
+    def test_is_job_complete_not_ready(self):
+        gblock = self.guest.get_block_device('vda')
+        disk = vconfig.LibvirtConfigGuestDisk()
+        disk.mirror = vconfig.LibvirtConfigGuestDiskMirror()
+        with mock.patch.object(self.guest, 'get_disk', return_value=disk):
+            self.domain.blockJobInfo.return_value = {
+                "type": 4,
+                "bandwidth": 18,
+                "cur": 100,
+                "end": 100}
+            is_complete = gblock.is_job_complete()
+            self.assertFalse(is_complete)
+
+    def test_is_job_complete_ready(self):
+        gblock = self.guest.get_block_device('vda')
+        disk = vconfig.LibvirtConfigGuestDisk()
+        disk.mirror = vconfig.LibvirtConfigGuestDiskMirror()
+        disk.mirror.ready = 'yes'
+        with mock.patch.object(self.guest, 'get_disk', return_value=disk):
+            self.domain.blockJobInfo.return_value = {
+                "type": 4,
+                "bandwidth": 18,
+                "cur": 100,
+                "end": 100}
+            is_complete = gblock.is_job_complete()
+            self.assertTrue(is_complete)
 
     def test_is_job_complete_no_job(self):
         self.domain.blockJobInfo.return_value = {}

nova/virt/libvirt/config.py

@@ -716,6 +716,7 @@ class LibvirtConfigGuestDisk(LibvirtConfigGuestDevice):
         self.backing_store = None
         self.device_addr = None
         self.boot_order = None
+        self.mirror = None
 
     def format_dom(self):
         dev = super(LibvirtConfigGuestDisk, self).format_dom()
@@ -875,6 +876,10 @@ class LibvirtConfigGuestDisk(LibvirtConfigGuestDevice):
                 self.device_addr = obj
             elif c.tag == 'boot':
                 self.boot_order = c.get('order')
+            elif c.tag == 'mirror':
+                m = LibvirtConfigGuestDiskMirror()
+                m.parse_dom(c)
+                self.mirror = m
 
 
 class LibvirtConfigGuestDiskBackingStore(LibvirtConfigObject):
@@ -1080,6 +1085,16 @@ class LibvirtConfigGuestFilesys(LibvirtConfigGuestDevice):
         return dev
 
 
+class LibvirtConfigGuestDiskMirror(LibvirtConfigObject):
+
+    def __init__(self, **kwargs):
+        super(LibvirtConfigGuestDiskMirror, self).__init__(**kwargs)
+        self.ready = None
+
+    def parse_dom(self, xmldoc):
+        self.ready = xmldoc.get('ready')
+
+
 class LibvirtConfigGuestIDMap(LibvirtConfigObject):
 
     def __init__(self, **kwargs):

nova/virt/libvirt/guest.py

@@ -315,7 +315,15 @@ class Guest(object):
             doc = etree.fromstring(self._domain.XMLDesc(0))
         except Exception:
             return None
+
+        # FIXME(lyarwood): Workaround for the device being either a target dev
+        # when called via swap_volume or source file when called via
+        # live_snapshot. This should be removed once both are refactored to use
+        # only the target dev of the device.
         node = doc.find("./devices/disk/target[@dev='%s'].." % device)
+        if node is None:
+            node = doc.find("./devices/disk/source[@file='%s'].." % device)
+
         if node is not None:
             conf = vconfig.LibvirtConfigGuestDisk()
             conf.parse_dom(node)
@@ -787,7 +795,14 @@ class BlockDevice(object):
         # The earliest tag which contains this commit is v2.3.0-rc1, so we
         # should be able to remove this workaround when MIN_LIBVIRT_VERSION
         # reaches 2.3.0, or we move to handling job events instead.
-        return status.end != 0 and status.cur == status.end
+        # NOTE(lyarwood): Use the mirror element to determine if we can pivot
+        # to the new disk once blockjobinfo reports progress as complete.
+        if status.end != 0 and status.cur == status.end:
+            disk = self._guest.get_disk(self._disk)
+            if disk and disk.mirror:
+                return disk.mirror.ready == 'yes'
+
+        return False
 
 
 class VCPUInfo(object):