Use a consistent naming scheme for XenAPI variables.

4 files changed, 155 insertions, 151 deletions

diff --git a/nova/virt/xenapi/vm_utils.py b/nova/virt/xenapi/vm_utils.py
index 8dd246178..f07b57796 100644
--- a/nova/virt/xenapi/vm_utils.py
+++ b/nova/virt/xenapi/vm_utils.py
@@ -202,13 +202,13 @@ class VMHelper(HelperBase):
     @classmethod
     def find_vbd_by_number(cls, session, vm_ref, number):
         """Get the VBD reference from the device number"""
-        vbds = session.get_xenapi().VM.get_VBDs(vm_ref)
-        if vbds:
-            for vbd in vbds:
+        vbd_refs = session.get_xenapi().VM.get_VBDs(vm_ref)
+        if vbd_refs:
+            for vbd_ref in vbd_refs:
                 try:
-                    vbd_rec = session.get_xenapi().VBD.get_record(vbd)
+                    vbd_rec = session.get_xenapi().VBD.get_record(vbd_ref)
                     if vbd_rec['userdevice'] == str(number):
-                        return vbd
+                        return vbd_ref
                 except cls.XenAPI.Failure, exc:
                     LOG.exception(exc)
         raise StorageError(_('VBD not found in instance %s') % vm_ref)
@@ -443,29 +443,29 @@ class VMHelper(HelperBase):
             vdi_size += MBR_SIZE_BYTES
 
         name_label = get_name_label_for_image(image)
-        vdi = cls.create_vdi(session, sr_ref, name_label, vdi_size, False)
+        vdi_ref = cls.create_vdi(session, sr_ref, name_label, vdi_size, False)
 
-        with_vdi_attached_here(session, vdi, False,
+        with_vdi_attached_here(session, vdi_ref, False,
                                lambda dev:
                                _stream_disk(dev, image_type,
                                             virtual_size, image_file))
         if image_type == ImageType.KERNEL_RAMDISK:
             #we need to invoke a plugin for copying VDI's
             #content into proper path
-            LOG.debug(_("Copying VDI %s to /boot/guest on dom0"), vdi)
+            LOG.debug(_("Copying VDI %s to /boot/guest on dom0"), vdi_ref)
             fn = "copy_kernel_vdi"
             args = {}
-            args['vdi-ref'] = vdi
+            args['vdi-ref'] = vdi_ref
             #let the plugin copy the correct number of bytes
             args['image-size'] = str(vdi_size)
             task = session.async_call_plugin('glance', fn, args)
             filename = session.wait_for_task(task, instance_id)
             #remove the VDI as it is not needed anymore
-            session.get_xenapi().VDI.destroy(vdi)
-            LOG.debug(_("Kernel/Ramdisk VDI %s destroyed"), vdi)
+            session.get_xenapi().VDI.destroy(vdi_ref)
+            LOG.debug(_("Kernel/Ramdisk VDI %s destroyed"), vdi_ref)
             return filename
         else:
-            return session.get_xenapi().VDI.get_uuid(vdi)
+            return session.get_xenapi().VDI.get_uuid(vdi_ref)
 
     @classmethod
     def determine_disk_image_type(cls, instance):
@@ -633,37 +633,38 @@ class VMHelper(HelperBase):
         return is_pv
 
     @classmethod
-    def lookup(cls, session, i):
+    def lookup(cls, session, name_label):
         """Look the instance i up, and returns it if available"""
-        vms = session.get_xenapi().VM.get_by_name_label(i)
-        n = len(vms)
+        vm_refs = session.get_xenapi().VM.get_by_name_label(name_label)
+        n = len(vm_refs)
         if n == 0:
             return None
         elif n > 1:
-            raise exception.Duplicate(_('duplicate name found: %s') % i)
+            raise exception.Duplicate(_('duplicate name found: %s') %
+                                        name_label)
         else:
-            return vms[0]
+            return vm_refs[0]
 
     @classmethod
-    def lookup_vm_vdis(cls, session, vm):
+    def lookup_vm_vdis(cls, session, vm_ref):
         """Look for the VDIs that are attached to the VM"""
         # Firstly we get the VBDs, then the VDIs.
         # TODO(Armando): do we leave the read-only devices?
-        vbds = session.get_xenapi().VM.get_VBDs(vm)
-        vdis = []
-        if vbds:
-            for vbd in vbds:
+        vbd_refs = session.get_xenapi().VM.get_VBDs(vm_ref)
+        vdi_refs = []
+        if vbd_refs:
+            for vbd_ref in vbd_refs:
                 try:
-                    vdi = session.get_xenapi().VBD.get_VDI(vbd)
+                    vdi_ref = session.get_xenapi().VBD.get_VDI(vbd_ref)
                     # Test valid VDI
-                    record = session.get_xenapi().VDI.get_record(vdi)
+                    record = session.get_xenapi().VDI.get_record(vdi_ref)
                     LOG.debug(_('VDI %s is still available'), record['uuid'])
                 except cls.XenAPI.Failure, exc:
                     LOG.exception(exc)
                 else:
-                    vdis.append(vdi)
-            if len(vdis) > 0:
-                return vdis
+                    vdi_refs.append(vdi_ref)
+            if len(vdi_refs) > 0:
+                return vdi_refs
             else:
                 return None
 
@@ -839,16 +840,16 @@ def safe_find_sr(session):
 def find_sr(session):
     """Return the storage repository to hold VM images"""
     host = session.get_xenapi_host()
-    srs = session.get_xenapi().SR.get_all()
-    for sr in srs:
-        sr_rec = session.get_xenapi().SR.get_record(sr)
+    sr_refs = session.get_xenapi().SR.get_all()
+    for sr_ref in sr_refs:
+        sr_rec = session.get_xenapi().SR.get_record(sr_ref)
         if not ('i18n-key' in sr_rec['other_config'] and
                 sr_rec['other_config']['i18n-key'] == 'local-storage'):
             continue
-        for pbd in sr_rec['PBDs']:
-            pbd_rec = session.get_xenapi().PBD.get_record(pbd)
+        for pbd_ref in sr_rec['PBDs']:
+            pbd_rec = session.get_xenapi().PBD.get_record(pbd_ref)
             if pbd_rec['host'] == host:
-                return sr
+                return sr_ref
     return None
 
 
@@ -873,11 +874,11 @@ def remap_vbd_dev(dev):
     return remapped_dev
 
 
-def with_vdi_attached_here(session, vdi, read_only, f):
+def with_vdi_attached_here(session, vdi_ref, read_only, f):
     this_vm_ref = get_this_vm_ref(session)
     vbd_rec = {}
     vbd_rec['VM'] = this_vm_ref
-    vbd_rec['VDI'] = vdi
+    vbd_rec['VDI'] = vdi_ref
     vbd_rec['userdevice'] = 'autodetect'
     vbd_rec['bootable'] = False
     vbd_rec['mode'] = read_only and 'RO' or 'RW'
@@ -888,28 +889,28 @@ def with_vdi_attached_here(session, vdi, read_only, f):
     vbd_rec['qos_algorithm_type'] = ''
     vbd_rec['qos_algorithm_params'] = {}
     vbd_rec['qos_supported_algorithms'] = []
-    LOG.debug(_('Creating VBD for VDI %s ... '), vdi)
-    vbd = session.get_xenapi().VBD.create(vbd_rec)
-    LOG.debug(_('Creating VBD for VDI %s done.'), vdi)
+    LOG.debug(_('Creating VBD for VDI %s ... '), vdi_ref)
+    vbd_ref = session.get_xenapi().VBD.create(vbd_rec)
+    LOG.debug(_('Creating VBD for VDI %s done.'), vdi_ref)
     try:
-        LOG.debug(_('Plugging VBD %s ... '), vbd)
-        session.get_xenapi().VBD.plug(vbd)
-        LOG.debug(_('Plugging VBD %s done.'), vbd)
-        orig_dev = session.get_xenapi().VBD.get_device(vbd)
-        LOG.debug(_('VBD %(vbd)s plugged as %(orig_dev)s') % locals())
+        LOG.debug(_('Plugging VBD %s ... '), vbd_ref)
+        session.get_xenapi().VBD.plug(vbd_ref)
+        LOG.debug(_('Plugging VBD %s done.'), vbd_ref)
+        orig_dev = session.get_xenapi().VBD.get_device(vbd_ref)
+        LOG.debug(_('VBD %(vbd_ref)s plugged as %(orig_dev)s') % locals())
         dev = remap_vbd_dev(orig_dev)
         if dev != orig_dev:
-            LOG.debug(_('VBD %(vbd)s plugged into wrong dev, '
+            LOG.debug(_('VBD %(vbd_ref)s plugged into wrong dev, '
                         'remapping to %(dev)s') % locals())
         return f(dev)
     finally:
-        LOG.debug(_('Destroying VBD for VDI %s ... '), vdi)
-        vbd_unplug_with_retry(session, vbd)
-        ignore_failure(session.get_xenapi().VBD.destroy, vbd)
-        LOG.debug(_('Destroying VBD for VDI %s done.'), vdi)
+        LOG.debug(_('Destroying VBD for VDI %s ... '), vdi_ref)
+        vbd_unplug_with_retry(session, vbd_ref)
+        ignore_failure(session.get_xenapi().VBD.destroy, vbd_ref)
+        LOG.debug(_('Destroying VBD for VDI %s done.'), vdi_ref)
 
 
-def vbd_unplug_with_retry(session, vbd):
+def vbd_unplug_with_retry(session, vbd_ref):
     """Call VBD.unplug on the given VBD, with a retry if we get
     DEVICE_DETACH_REJECTED.  For reasons which I don't understand, we're
     seeing the device still in use, even when all processes using the device
@@ -917,7 +918,7 @@ def vbd_unplug_with_retry(session, vbd):
     # FIXME(sirp): We can use LoopingCall here w/o blocking sleep()
     while True:
         try:
-            session.get_xenapi().VBD.unplug(vbd)
+            session.get_xenapi().VBD.unplug(vbd_ref)
             LOG.debug(_('VBD.unplug successful first time.'))
             return
         except VMHelper.XenAPI.Failure, e:
diff --git a/nova/virt/xenapi/vmops.py b/nova/virt/xenapi/vmops.py
index aa4372c3d..fcb290d03 100644
--- a/nova/virt/xenapi/vmops.py
+++ b/nova/virt/xenapi/vmops.py
@@ -55,12 +55,12 @@ class VMOps(object):
 
     def list_instances(self):
         """List VM instances"""
-        vms = []
-        for vm in self._session.get_xenapi().VM.get_all():
-            rec = self._session.get_xenapi().VM.get_record(vm)
-            if not rec["is_a_template"] and not rec["is_control_domain"]:
-                vms.append(rec["name_label"])
-        return vms
+        vm_refs = []
+        for vm_ref in self._session.get_xenapi().VM.get_all():
+            vm_rec = self._session.get_xenapi().VM.get_record(vm_ref)
+            if not vm_rec["is_a_template"] and not vm_rec["is_control_domain"]:
+                vm_refs.append(vm_rec["name_label"])
+        return vm_refs
 
     def _start(self, instance, vm_ref=None):
         """Power on a VM instance"""
@@ -87,8 +87,8 @@ class VMOps(object):
     def _spawn_with_disk(self, instance, vdi_uuid):
         """Create VM instance"""
         instance_name = instance.name
-        vm = VMHelper.lookup(self._session, instance_name)
-        if vm is not None:
+        vm_ref = VMHelper.lookup(self._session, instance_name)
+        if vm_ref is not None:
             raise exception.Duplicate(_('Attempted to create'
                     ' non-unique name %s') % instance_name)
 
@@ -366,8 +366,8 @@ class VMOps(object):
 
     def reboot(self, instance):
         """Reboot VM instance"""
-        vm = self._get_vm_opaque_ref(instance)
-        task = self._session.call_xenapi('Async.VM.clean_reboot', vm)
+        vm_ref = self._get_vm_opaque_ref(instance)
+        task = self._session.call_xenapi('Async.VM.clean_reboot', vm_ref)
         self._session.wait_for_task(task, instance.id)
 
     def set_admin_password(self, instance, new_pass):
@@ -434,7 +434,7 @@ class VMOps(object):
             raise RuntimeError(resp_dict['message'])
         return resp_dict['message']
 
-    def _shutdown(self, instance, vm, hard=True):
+    def _shutdown(self, instance, vm_ref, hard=True):
         """Shutdown an instance"""
         state = self.get_info(instance['name'])['state']
         if state == power_state.SHUTDOWN:
@@ -448,31 +448,33 @@ class VMOps(object):
         try:
             task = None
             if hard:
-                task = self._session.call_xenapi("Async.VM.hard_shutdown", vm)
+                task = self._session.call_xenapi("Async.VM.hard_shutdown",
+                                                 vm_ref)
             else:
-                task = self._session.call_xenapi('Async.VM.clean_shutdown', vm)
+                task = self._session.call_xenapi("Async.VM.clean_shutdown",
+                                                 vm_ref)
             self._session.wait_for_task(task, instance.id)
         except self.XenAPI.Failure, exc:
             LOG.exception(exc)
 
-    def _destroy_vdis(self, instance, vm):
-        """Destroys all VDIs associated with a VM """
+    def _destroy_vdis(self, instance, vm_ref):
+        """Destroys all VDIs associated with a VM"""
         instance_id = instance.id
         LOG.debug(_("Destroying VDIs for Instance %(instance_id)s")
                   % locals())
-        vdis = VMHelper.lookup_vm_vdis(self._session, vm)
+        vdi_refs = VMHelper.lookup_vm_vdis(self._session, vm_ref)
 
-        if not vdis:
+        if not vdi_refs:
             return
 
-        for vdi in vdis:
+        for vdi_ref in vdi_refs:
             try:
-                task = self._session.call_xenapi('Async.VDI.destroy', vdi)
+                task = self._session.call_xenapi('Async.VDI.destroy', vdi_ref)
                 self._session.wait_for_task(task, instance.id)
             except self.XenAPI.Failure, exc:
                 LOG.exception(exc)
 
-    def _destroy_kernel_ramdisk(self, instance, vm):
+    def _destroy_kernel_ramdisk(self, instance, vm_ref):
         """
         Three situations can occur:
 
@@ -499,8 +501,8 @@ class VMOps(object):
                   "both" % locals()))
 
         # 3. We have both kernel and ramdisk
-        (kernel, ramdisk) = VMHelper.lookup_kernel_ramdisk(
-            self._session, vm)
+        (kernel, ramdisk) = VMHelper.lookup_kernel_ramdisk(self._session,
+                                                           vm_ref)
 
         LOG.debug(_("Removing kernel/ramdisk files"))
 
@@ -511,11 +513,11 @@ class VMOps(object):
 
         LOG.debug(_("kernel/ramdisk files removed"))
 
-    def _destroy_vm(self, instance, vm):
-        """Destroys a VM record """
+    def _destroy_vm(self, instance, vm_ref):
+        """Destroys a VM record"""
         instance_id = instance.id
         try:
-            task = self._session.call_xenapi('Async.VM.destroy', vm)
+            task = self._session.call_xenapi('Async.VM.destroy', vm_ref)
             self._session.wait_for_task(task, instance_id)
         except self.XenAPI.Failure, exc:
             LOG.exception(exc)
@@ -531,10 +533,10 @@ class VMOps(object):
         """
         instance_id = instance.id
         LOG.info(_("Destroying VM for Instance %(instance_id)s") % locals())
-        vm = VMHelper.lookup(self._session, instance.name)
-        return self._destroy(instance, vm, shutdown=True)
+        vm_ref = VMHelper.lookup(self._session, instance.name)
+        return self._destroy(instance, vm_ref, shutdown=True)
 
-    def _destroy(self, instance, vm, shutdown=True,
+    def _destroy(self, instance, vm_ref, shutdown=True,
                  destroy_kernel_ramdisk=True):
         """
         Destroys VM instance by performing:
@@ -544,17 +546,17 @@ class VMOps(object):
             3. Destroying kernel and ramdisk files (if necessary)
             4. Destroying that actual VM record
         """
-        if vm is None:
+        if vm_ref is None:
             LOG.warning(_("VM is not present, skipping destroy..."))
             return
 
         if shutdown:
-            self._shutdown(instance, vm)
+            self._shutdown(instance, vm_ref)
 
-        self._destroy_vdis(instance, vm)
+        self._destroy_vdis(instance, vm_ref)
         if destroy_kernel_ramdisk:
-            self._destroy_kernel_ramdisk(instance, vm)
-        self._destroy_vm(instance, vm)
+            self._destroy_kernel_ramdisk(instance, vm_ref)
+        self._destroy_vm(instance, vm_ref)
 
     def _wait_with_callback(self, instance_id, task, callback):
         ret = None
@@ -566,26 +568,27 @@ class VMOps(object):
 
     def pause(self, instance, callback):
         """Pause VM instance"""
-        vm = self._get_vm_opaque_ref(instance)
-        task = self._session.call_xenapi('Async.VM.pause', vm)
+        vm_ref = self._get_vm_opaque_ref(instance)
+        task = self._session.call_xenapi('Async.VM.pause', vm_ref)
         self._wait_with_callback(instance.id, task, callback)
 
     def unpause(self, instance, callback):
         """Unpause VM instance"""
-        vm = self._get_vm_opaque_ref(instance)
-        task = self._session.call_xenapi('Async.VM.unpause', vm)
+        vm_ref = self._get_vm_opaque_ref(instance)
+        task = self._session.call_xenapi('Async.VM.unpause', vm_ref)
         self._wait_with_callback(instance.id, task, callback)
 
     def suspend(self, instance, callback):
         """suspend the specified instance"""
-        vm = self._get_vm_opaque_ref(instance)
-        task = self._session.call_xenapi('Async.VM.suspend', vm)
+        vm_ref = self._get_vm_opaque_ref(instance)
+        task = self._session.call_xenapi('Async.VM.suspend', vm_ref)
         self._wait_with_callback(instance.id, task, callback)
 
     def resume(self, instance, callback):
         """resume the specified instance"""
-        vm = self._get_vm_opaque_ref(instance)
-        task = self._session.call_xenapi('Async.VM.resume', vm, False, True)
+        vm_ref = self._get_vm_opaque_ref(instance)
+        task = self._session.call_xenapi('Async.VM.resume', vm_ref, False,
+                                         True)
         self._wait_with_callback(instance.id, task, callback)
 
     def rescue(self, instance, callback):
@@ -595,29 +598,26 @@ class VMOps(object):
             - spawn a rescue VM (the vm name-label will be instance-N-rescue)
 
         """
-        rescue_vm = VMHelper.lookup(self._session, instance.name + "-rescue")
-        if rescue_vm:
+        rescue_vm_ref = VMHelper.lookup(self._session,
+                                        instance.name + "-rescue")
+        if rescue_vm_ref:
             raise RuntimeError(_(
                 "Instance is already in Rescue Mode: %s" % instance.name))
 
-        vm = self._get_vm_opaque_ref(instance)
-        self._shutdown(instance, vm)
-        self._acquire_bootlock(vm)
+        vm_ref = self._get_vm_opaque_ref(instance)
+        self._shutdown(instance, vm_ref)
+        self._acquire_bootlock(vm_ref)
 
         instance._rescue = True
         self.spawn(instance)
-        rescue_vm = self._get_vm_opaque_ref(instance)
+        rescue_vm_ref = self._get_vm_opaque_ref(instance)
 
-        vbd = self._session.get_xenapi().VM.get_VBDs(vm)[0]
-        vdi_ref = self._session.get_xenapi().VBD.get_record(vbd)["VDI"]
-        vbd_ref = VMHelper.create_vbd(
-            self._session,
-            rescue_vm,
-            vdi_ref,
-            1,
-            False)
+        vbd_ref = self._session.get_xenapi().VM.get_VBDs(vm_ref)[0]
+        vdi_ref = self._session.get_xenapi().VBD.get_record(vbd_ref)["VDI"]
+        rescue_vbd_ref = VMHelper.create_vbd(self._session, rescue_vm_ref,
+                                             vdi_ref, 1, False)
 
-        self._session.call_xenapi("Async.VBD.plug", vbd_ref)
+        self._session.call_xenapi("Async.VBD.plug", rescue_vbd_ref)
 
     def unrescue(self, instance, callback):
         """Unrescue the specified instance
@@ -626,51 +626,53 @@ class VMOps(object):
             - release the bootlock to allow the instance VM to start
 
         """
-        rescue_vm = VMHelper.lookup(self._session, instance.name + "-rescue")
+        rescue_vm_ref = VMHelper.lookup(self._session,
+                                    instance.name + "-rescue")
 
-        if not rescue_vm:
+        if not rescue_vm_ref:
             raise exception.NotFound(_(
                 "Instance is not in Rescue Mode: %s" % instance.name))
 
-        original_vm = self._get_vm_opaque_ref(instance)
-        vbds = self._session.get_xenapi().VM.get_VBDs(rescue_vm)
+        original_vm_ref = self._get_vm_opaque_ref(instance)
+        vbd_refs = self._session.get_xenapi().VM.get_VBDs(rescue_vm_ref)
 
         instance._rescue = False
 
-        for vbd_ref in vbds:
-            vbd = self._session.get_xenapi().VBD.get_record(vbd_ref)
-            if vbd["userdevice"] == "1":
+        for vbd_ref in vbd_refs:
+            _vbd_ref = self._session.get_xenapi().VBD.get_record(vbd_ref)
+            if _vbd_ref["userdevice"] == "1":
                 VMHelper.unplug_vbd(self._session, vbd_ref)
                 VMHelper.destroy_vbd(self._session, vbd_ref)
 
-        task1 = self._session.call_xenapi("Async.VM.hard_shutdown", rescue_vm)
+        task1 = self._session.call_xenapi("Async.VM.hard_shutdown",
+                                          rescue_vm_ref)
         self._session.wait_for_task(task1, instance.id)
 
-        vdis = VMHelper.lookup_vm_vdis(self._session, rescue_vm)
-        for vdi in vdis:
+        vdi_refs = VMHelper.lookup_vm_vdis(self._session, rescue_vm_ref)
+        for vdi_ref in vdi_refs:
             try:
-                task = self._session.call_xenapi('Async.VDI.destroy', vdi)
+                task = self._session.call_xenapi('Async.VDI.destroy', vdi_ref)
                 self._session.wait_for_task(task, instance.id)
             except self.XenAPI.Failure:
                 continue
 
-        task2 = self._session.call_xenapi('Async.VM.destroy', rescue_vm)
+        task2 = self._session.call_xenapi('Async.VM.destroy', rescue_vm_ref)
         self._session.wait_for_task(task2, instance.id)
 
-        self._release_bootlock(original_vm)
-        self._start(instance, original_vm)
+        self._release_bootlock(original_vm_ref)
+        self._start(instance, original_vm_ref)
 
     def get_info(self, instance):
         """Return data about VM instance"""
-        vm = self._get_vm_opaque_ref(instance)
-        rec = self._session.get_xenapi().VM.get_record(vm)
-        return VMHelper.compile_info(rec)
+        vm_ref = self._get_vm_opaque_ref(instance)
+        vm_rec = self._session.get_xenapi().VM.get_record(vm_ref)
+        return VMHelper.compile_info(vm_rec)
 
     def get_diagnostics(self, instance):
         """Return data about VM diagnostics"""
-        vm = self._get_vm_opaque_ref(instance)
-        rec = self._session.get_xenapi().VM.get_record(vm)
-        return VMHelper.compile_diagnostics(self._session, rec)
+        vm_ref = self._get_vm_opaque_ref(instance)
+        vm_rec = self._session.get_xenapi().VM.get_record(vm_ref)
+        return VMHelper.compile_diagnostics(self._session, vm_rec)
 
     def get_console_output(self, instance):
         """Return snapshot of console"""
@@ -693,9 +695,9 @@ class VMOps(object):
         # at this stage even though they aren't implemented because these will
         # be needed for multi-nic and there was no sense writing it for single
         # network/single IP and then having to turn around and re-write it
-        vm_opaque_ref = self._get_vm_opaque_ref(instance.id)
+        vm_ref = self._get_vm_opaque_ref(instance.id)
         logging.debug(_("injecting network info to xenstore for vm: |%s|"),
-                                                             vm_opaque_ref)
+                        vm_ref)
         admin_context = context.get_admin_context()
         IPs = db.fixed_ip_get_all_by_instance(admin_context, instance['id'])
         networks = db.network_get_all_by_instance(admin_context,
@@ -726,11 +728,10 @@ class VMOps(object):
                 'ips': [ip_dict(ip) for ip in network_IPs],
                 'ip6s': [ip6_dict(ip) for ip in network_IPs]}
 
-            self.write_to_param_xenstore(vm_opaque_ref, {location: mapping})
+            self.write_to_param_xenstore(vm_ref, {location: mapping})
 
             try:
-                self.write_to_xenstore(vm_opaque_ref, location,
-                                                      mapping['location'])
+                self.write_to_xenstore(vm_ref, location, mapping['location'])
             except KeyError:
                 # catch KeyError for domid if instance isn't running
                 pass
@@ -742,8 +743,8 @@ class VMOps(object):
         Creates vifs for an instance
 
         """
-        vm_opaque_ref = self._get_vm_opaque_ref(instance.id)
-        logging.debug(_("creating vif(s) for vm: |%s|"), vm_opaque_ref)
+        vm_ref = self._get_vm_opaque_ref(instance.id)
+        logging.debug(_("creating vif(s) for vm: |%s|"), vm_ref)
         if networks is None:
             networks = db.network_get_all_by_instance(admin_context,
                                                       instance['id'])
@@ -763,12 +764,8 @@ class VMOps(object):
                 except AttributeError:
                     device = "0"
 
-                VMHelper.create_vif(
-                    self._session,
-                    vm_opaque_ref,
-                    network_ref,
-                    instance.mac_address,
-                    device)
+                VMHelper.create_vif(self._session, vm_ref, network_ref,
+                                    instance.mac_address, device)
 
     def reset_network(self, instance):
         """
@@ -832,9 +829,9 @@ class VMOps(object):
         Any errors raised by the plugin will in turn raise a RuntimeError here.
         """
         instance_id = vm.id
-        vm = self._get_vm_opaque_ref(vm)
-        rec = self._session.get_xenapi().VM.get_record(vm)
-        args = {'dom_id': rec['domid'], 'path': path}
+        vm_ref = self._get_vm_opaque_ref(vm)
+        vm_rec = self._session.get_xenapi().VM.get_record(vm_ref)
+        args = {'dom_id': vm_rec['domid'], 'path': path}
         args.update(addl_args)
         try:
             task = self._session.async_call_plugin(plugin, method, args)
@@ -914,9 +911,9 @@ class VMOps(object):
         value for 'keys' is passed, the returned dict is filtered to only
         return the values for those keys.
         """
-        vm = self._get_vm_opaque_ref(instance_or_vm)
+        vm_ref = self._get_vm_opaque_ref(instance_or_vm)
         data = self._session.call_xenapi_request('VM.get_xenstore_data',
-                (vm, ))
+                (vm_ref, ))
         ret = {}
         if keys is None:
             keys = data.keys()
@@ -934,11 +931,11 @@ class VMOps(object):
         """Takes a key/value pair and adds it to the xenstore parameter
         record for the given vm instance. If the key exists in xenstore,
         it is overwritten"""
-        vm = self._get_vm_opaque_ref(instance_or_vm)
+        vm_ref = self._get_vm_opaque_ref(instance_or_vm)
         self.remove_from_param_xenstore(instance_or_vm, key)
         jsonval = json.dumps(val)
         self._session.call_xenapi_request('VM.add_to_xenstore_data',
-                (vm, key, jsonval))
+                                          (vm_ref, key, jsonval))
 
     def write_to_param_xenstore(self, instance_or_vm, mapping):
         """Takes a dict and writes each key/value pair to the xenstore
@@ -953,14 +950,14 @@ class VMOps(object):
         them from the xenstore parameter record data for the given VM.
         If the key doesn't exist, the request is ignored.
         """
-        vm = self._get_vm_opaque_ref(instance_or_vm)
+        vm_ref = self._get_vm_opaque_ref(instance_or_vm)
         if isinstance(key_or_keys, basestring):
             keys = [key_or_keys]
         else:
             keys = key_or_keys
         for key in keys:
             self._session.call_xenapi_request('VM.remove_from_xenstore_data',
-                    (vm, key))
+                                              (vm_ref, key))
 
     def clear_param_xenstore(self, instance_or_vm):
         """Removes all data from the xenstore parameter record for this VM."""
diff --git a/nova/virt/xenapi/volume_utils.py b/nova/virt/xenapi/volume_utils.py
index d5ebd29d5..72284ac02 100644
--- a/nova/virt/xenapi/volume_utils.py
+++ b/nova/virt/xenapi/volume_utils.py
@@ -117,16 +117,16 @@ class VolumeHelper(HelperBase):
     def introduce_vdi(cls, session, sr_ref):
         """Introduce VDI in the host"""
         try:
-            vdis = session.get_xenapi().SR.get_VDIs(sr_ref)
+            vdi_refs = session.get_xenapi().SR.get_VDIs(sr_ref)
         except cls.XenAPI.Failure, exc:
             LOG.exception(exc)
             raise StorageError(_('Unable to introduce VDI on SR %s') % sr_ref)
         try:
-            vdi_rec = session.get_xenapi().VDI.get_record(vdis[0])
+            vdi_rec = session.get_xenapi().VDI.get_record(vdi_refs[0])
         except cls.XenAPI.Failure, exc:
             LOG.exception(exc)
             raise StorageError(_('Unable to get record'
-                                 ' of VDI %s on') % vdis[0])
+                                 ' of VDI %s on') % vdi_refs[0])
         else:
             try:
                 return session.get_xenapi().VDI.introduce(
diff --git a/nova/virt/xenapi_conn.py b/nova/virt/xenapi_conn.py
index b63a5f8c3..bfe290be3 100644
--- a/nova/virt/xenapi_conn.py
+++ b/nova/virt/xenapi_conn.py
@@ -49,6 +49,12 @@ reactor thread if the VM.get_by_name_label or VM.get_record calls block.
                              address for the nova-volume host
 :target_port:                iSCSI Target Port, 3260 Default
 :iqn_prefix:                 IQN Prefix, e.g. 'iqn.2010-10.org.openstack'
+
+**Variable Naming Scheme**
+
+- suffix "_ref" for opaque references
+- suffix "_uuid" for UUIDs
+- suffix "_rec" for record objects
 """
 
 import sys