hypervisor.kvm: fix domain XML update while running

When we update a VM configuration while it is running, for example a change in
the network interfaces, we recreate a domain from the running XML which is fine
but this is not valid anymore when the VM is stopped.
So in the latter case, we keep an attribute on the VM indicating if we need to
recreate the VM instance from the XML when it stops.

cloudcontrol/node/hypervisor/domains/__init__.py

@@ -96,6 +96,8 @@ class VirtualMachine(object):
         self.from_stream = None  # buffer
         self.stream_handling = 0  # libvirt stream event mask
 
+        self.redefine_on_stop = False  # for XML update (see KVM class)
+
     @property
     def state(self):
         return self._state

cloudcontrol/node/hypervisor/kvm.py

@@ -120,19 +120,22 @@ class KVM(object):
                 return
             # update Storage pools in case VM has volumes that were created
             self.storage.update()
+            # if vm is redefined while running we need to refresh its devices
+            # when stopped
+            redefine_on_stop = False
             if dom.name() in self.domains:
                 # sometimes libvirt send us the same event multiple times
                 # this can be the result of a change in the domain configuration
                 # we first remove the old domain
                 vm = self.domains.pop(dom.name())
                 self.handler.tag_db.remove_sub_object(vm.name)
+                if vm.state not in ('stopped', 'crashed'):
+                    # if the vm was updated while it was "on", then the
+                    # modifications will not be reflected since we construct the
+                    # object/tags from running XML
+                    redefine_on_stop = True
                 logger.debug('Domain %s recreated', dom.name())
-            vm = VirtualMachine(dom, self)
-            logger.info('Created domain %s', vm.name)
-            self.domains[vm.name] = vm
-            self.handler.tag_db.add_sub_object(vm.name, vm.tags.itervalues(),
-                                               'vm')
-            self.update_domain_count()
+            self.vm_register(dom, redefine_on_stop)
         elif event == 'Removed':
             vm_name = dom.name()
             self.vm_unregister(vm_name)
@@ -155,9 +158,28 @@ class KVM(object):
                 else:
                     logger.info('Domain change state from %s to %s', vm.state,
                                  state)
-                    vm.state = state
+                    if event == 'Stopped' and vm.redefine_on_stop:
+                        # if the vm was changed while it was running, then we
+                        # need to recreate it now as stated above
+                        self.vm_unregister(vm.name)
+                        self.vm_register(dom)
+                    else:
+                        vm.state = state
                     self.update_domain_count()
 
+    def vm_register(self, dom, redefine_on_stop=False):
+        """Register a VM to the hypervisor object.
+
+        :param dom: libvirt domain instance
+        :param redefine_on_stop: if we need to reread the domain XML on stop
+        """
+        vm = VirtualMachine(dom, self)
+        logger.info('Created domain %s', vm.name)
+        vm.redefine_on_stop = redefine_on_stop
+        self.domains[vm.name] = vm
+        self.handler.tag_db.add_sub_object(vm.name, vm.tags.itervalues(), 'vm')
+        self.update_domain_count()
+
     def vm_unregister(self, name):
         """Unregister a VM from the cc-server and remove it from the index."""
         try: