Fix behaviour of split_cell_and_item

If you try to split a cell and item, with no path!to!cell@ in it, it'll
now return None for the cell, instead causing a ValueError when trying
to split the result.

Change-Id: I228b9f3b0f63f8c7a6004b3206f5312ed2a878bc
Fixes: bug #1153841

nova/cells/manager.py

@@ -277,12 +277,11 @@ class CellsManager(manager.Manager):
         if host is None:
             cell_name = None
         else:
-            result = cells_utils.split_cell_and_item(host)
-            cell_name = result[0]
-            if len(result) > 1:
-                host = result[1]
-            else:
-                host = None
+            cell_name, host = cells_utils.split_cell_and_item(host)
+            # If no cell name was given, assume that the host name is the
+            # cell_name and that the target is all hosts
+            if cell_name is None:
+                cell_name, host = host, cell_name
         responses = self.msg_runner.task_log_get_all(ctxt, cell_name,
                 task_name, period_beginning, period_ending,
                 host=host, state=state)

nova/cells/utils.py

@@ -56,12 +56,18 @@ def get_instances_to_sync(context, updated_since=None, project_id=None,
 
 def cell_with_item(cell_name, item):
     """Turn cell_name and item into <cell_name>@<item>."""
+    if cell_name is None:
+        return item
     return cell_name + _CELL_ITEM_SEP + str(item)
 
 
 def split_cell_and_item(cell_and_item):
     """Split a combined cell@item and return them."""
-    return cell_and_item.rsplit(_CELL_ITEM_SEP, 1)
+    result = cell_and_item.rsplit(_CELL_ITEM_SEP, 1)
+    if len(result) == 1:
+        return (None, cell_and_item)
+    else:
+        return result
 
 
 def _add_cell_to_service(service, cell_name):

nova/compute/cells_api.py

@@ -615,10 +615,7 @@ class HostAPI(compute_api.HostAPI):
         this call to cells, as we have instance information here in
         the API cell.
         """
-        try:
-            cell_name, host_name = cells_utils.split_cell_and_item(host_name)
-        except ValueError:
-            cell_name = None
+        cell_name, host_name = cells_utils.split_cell_and_item(host_name)
         instances = super(HostAPI, self).instance_get_all_by_host(context,
                                                                   host_name)
         if cell_name:

nova/tests/cells/test_cells_utils.py

@@ -80,3 +80,26 @@ class CellsUtilsTestCase(test.TestCase):
                 {'changes-since': 'fake-updated-since',
                  'project_id': 'fake-project'})
         self.assertEqual(call_info['shuffle'], 2)
+
+    def test_split_cell_and_item(self):
+        path = 'australia', 'queensland', 'gold_coast'
+        cell = cells_utils._PATH_CELL_SEP.join(path)
+        item = 'host_5'
+        together = cells_utils.cell_with_item(cell, item)
+        self.assertEqual(cells_utils._CELL_ITEM_SEP.join([cell, item]),
+                         together)
+
+        # Test normal usage
+        result_cell, result_item = cells_utils.split_cell_and_item(together)
+        self.assertEqual(cell, result_cell)
+        self.assertEqual(item, result_item)
+
+        # Test with no cell
+        cell = None
+        together = cells_utils.cell_with_item(cell, item)
+        self.assertEqual(item, together)
+        print together
+        result_cell, result_item = cells_utils.split_cell_and_item(together)
+        print result_cell, result_item
+        self.assertEqual(cell, result_cell)
+        self.assertEqual(item, result_item)