connection: Add infrastructure to blacklist failing objects

It happens every now and then that a libvirt bug means calling XMLDesc
on an object will always fail. For example:

https://bugzilla.redhat.com/show_bug.cgi?id=1225771

We don't handle this very well and it can bleed into many other parts of
the code in a bad way. So if the initial polling of the object fails,
blacklist it entirely and ignore it for all future polling.

virtManager/connection.py

@@ -54,6 +54,7 @@ class _ObjectList(vmmGObject):
         vmmGObject.__init__(self)
 
         self._objects = []
+        self._blacklist = []
         self._lock = threading.Lock()
 
     def _cleanup(self):
@@ -69,6 +70,29 @@ class _ObjectList(vmmGObject):
         finally:
             self._lock.release()
 
+    def _blacklist_key(self, obj):
+        return str(obj.__class__) + obj.get_connkey()
+
+    def add_blacklist(self, obj):
+        """
+        Add an object to the blacklist. Basically a list of objects we
+        choose not to poll, because they threw an error at init time
+
+        :param obj: vmmLibvirtObject to blacklist
+        :returns: True if object added, False if object was already in list
+        """
+        if self.in_blacklist(obj):
+            return False
+        self._blacklist.append(self._blacklist_key(obj))
+        return True
+
+    def in_blacklist(self, obj):
+        """
+        :param obj: vmmLibvirtObject to check
+        :returns: True if object is in the blacklist
+        """
+        return self._blacklist_key(obj) in self._blacklist
+
     def remove(self, obj):
         """
         Remove an object from the list.
@@ -82,6 +106,10 @@ class _ObjectList(vmmGObject):
             # Identity check is sufficient here, since we should never be
             # asked to remove an object that wasn't at one point in the list.
             if obj not in self._objects:
+                if self.in_blacklist(obj):
+                    self._blacklist.remove(self._blacklist_key(obj))
+                    return True
+
                 return False
 
             self._objects.remove(obj)
@@ -990,13 +1018,19 @@ class vmmConnection(vmmGObject):
                 self.emit("nodedev-removed", obj.get_connkey())
             obj.cleanup()
 
-    def _new_object_cb(self, obj):
+    def _new_object_cb(self, obj, initialize_failed):
         if not self._backend.is_open():
             return
 
         try:
             class_name = obj.class_name()
 
+            if initialize_failed:
+                logging.debug("Blacklisting %s=%s", class_name, obj.get_name())
+                if self._objects.add_blacklist(obj) is False:
+                    logging.debug("Object already blacklisted?")
+                return
+
             if not self._objects.add(obj):
                 logging.debug("New %s=%s requested, but it's already tracked.",
                     class_name, obj.get_name())
@@ -1074,6 +1108,7 @@ class vmmConnection(vmmGObject):
 
             gone_objects.extend(gone)
             preexisting_objects.extend([o for o in master if o not in new])
+            new = [n for n in new if not self._objects.in_blacklist(n)]
             return new
 
         new_vms = _process_objects(self._update_vms(pollvm))

virtManager/libvirtobject.py

@@ -28,7 +28,7 @@ from .baseclass import vmmGObject
 class vmmLibvirtObject(vmmGObject):
     __gsignals__ = {
         "state-changed": (GObject.SignalFlags.RUN_FIRST, None, []),
-        "initialized": (GObject.SignalFlags.RUN_FIRST, None, []),
+        "initialized": (GObject.SignalFlags.RUN_FIRST, None, [bool]),
     }
 
     _STATUS_ACTIVE = 1
@@ -185,14 +185,16 @@ class vmmLibvirtObject(vmmGObject):
         if self.__initialized:
             return
 
+        initialize_failed = False
         try:
             self._init_libvirt_state()
         except:
             logging.debug("Error initializing libvirt state for %s", self,
                 exc_info=True)
+            initialize_failed = True
 
         self.__initialized = True
-        self.idle_emit("initialized")
+        self.idle_emit("initialized", initialize_failed)
 
 
     ###################