connection: Poll for node devices, rather than fetch on demand

This should hopefully be much less taxing on bandwidth, since hostdevices
shouldn't change too much, so every tick we only need to compare a couples
lists.

src/virtManager/connection.py

@@ -72,6 +72,11 @@ class vmmConnection(gobject.GObject):
         "interface-stopped": (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE,
                               [str, str]),
 
+        "nodedev-added": (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE,
+                          [str, str]),
+        "nodedev-removed": (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE,
+                            [str, str]),
+
         "resources-sampled": (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE,
                               []),
         "state-changed": (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE,
@@ -105,8 +110,11 @@ class vmmConnection(gobject.GObject):
         self.network_capable = None
         self.storage_capable = None
         self.interface_capable = None
+        self._nodedev_capable = None
         self.dom_xml_flags = None
 
+        # Physical network interfaces: name -> virtinst.NodeDevice
+        self.nodedevs = {}
         # Physical network interfaces: name (eth0) -> vmmNetDevice
         self.netdevs = {}
         # Connection Storage pools: name -> vmmInterface
@@ -312,7 +320,9 @@ class vmmConnection(gobject.GObject):
         return virtinst.util.is_storage_capable(self.vmm)
 
     def is_nodedev_capable(self):
-        return virtinst.NodeDeviceParser.is_nodedev_capable(self.vmm)
+        if self._nodedev_capable == None:
+            self._nodedev_capable = virtinst.NodeDeviceParser.is_nodedev_capable(self.vmm)
+        return self._nodedev_capable
 
     def set_dom_flags(self, vm):
         if self.dom_xml_flags != None:
@@ -402,19 +412,16 @@ class vmmConnection(gobject.GObject):
     def get_interface(self, name):
         return self.interfaces[name]
     def get_devices(self, devtype=None, devcap=None):
-        if not self.is_nodedev_capable():
-            return []
-
-        devs = self.vmm.listDevices(devtype, 0)
         retdevs = []
-
-        for name in devs:
-            dev = self.vmm.nodeDeviceLookupByName(name)
-            vdev = virtinst.NodeDeviceParser.parse(dev.XMLDesc(0))
-
-            if devcap and vdev.capability_type != devcap:
+        for vdev in self.nodedevs.values():
+            if devtype and vdev.device_type != devtype:
                 continue
 
+            if devcap:
+                if (not hasattr(vdev, "capability_type") or
+                    vdev.capability_type != devcap):
+                    continue
+
             retdevs.append(vdev)
 
         return retdevs
@@ -931,6 +938,49 @@ class vmmConnection(gobject.GObject):
 
         return (stop, start, orig, new, current)
 
+    def _update_nodedevs(self):
+        orig = self.nodedevs
+        current = {}
+        new = []
+        newActiveNames = []
+
+        if self._nodedev_capable == None:
+            self._nodedev_capable = self.is_nodedev_capable()
+            if self._nodedev_capable is False:
+                logging.debug("Connection doesn't seem to support nodedev "
+                              "APIs. Skipping all nodedev polling.")
+
+        if not self.is_nodedev_capable():
+            return (orig, new, current)
+
+        try:
+            newActiveNames = self.vmm.listDevices(None, 0)
+        except:
+            logging.exception("Unable to list nodedev devices")
+
+        def check_obj(name):
+            key = name
+
+            if not orig.has_key(key):
+                obj = self.vmm.nodeDeviceLookupByName(name)
+                vdev = virtinst.NodeDeviceParser.parse(obj.XMLDesc(0))
+
+                # Object is brand new this tick period
+                current[key] = vdev
+                new.append(key)
+
+            else:
+                # Previously known object, remove it from the orig list
+                current[key] = orig[key]
+                del orig[key]
+
+        for name in newActiveNames:
+            try:
+                check_obj(name)
+            except libvirt.libvirtError:
+                logging.exception("Couldn't fetch nodedev '%s'" % name)
+
+        return (orig, new, current)
 
     def _update_vms(self):
         """
@@ -1060,6 +1110,9 @@ class vmmConnection(gobject.GObject):
         (stopInterfaces, startInterfaces, oldInterfaces,
          newInterfaces, self.interfaces) = self._update_interfaces()
 
+        # Update nodedevice list
+        (oldNodedevs, newNodedevs, self.nodedevs) = self._update_nodedevs()
+
         # Poll for changed/new/removed VMs
         (startVMs, newVMs, oldVMs,
          self.vms, self.activeUUIDs) = self._update_vms()
@@ -1110,6 +1163,11 @@ class vmmConnection(gobject.GObject):
             for name in stopInterfaces:
                 self.emit("interface-stopped", self.uri, name)
 
+            # Update nodedev list
+            for name in oldNodedevs:
+                self.emit("nodedev-removed", self.uri, name)
+            for name in newNodedevs:
+                self.emit("nodedev-added", self.uri, name)
 
         gobject.idle_add(tick_send_signals)