Deprecate compute_api_class option in the config

Add a function "get_compute_api_class_name" within nova.compute
that returns nova.compute.cells_api.ComputeCellsAPI if cell is
enabled and this cell is an API cell, and returns compute.api.API
otherwise.
Add an option "cell_type" to the config in group "cells".
Use the default value of "cell_type" (None) for legacy configuration.

Change-Id: I32f5ccf789c657b563c165bfa8244e819b1a79a6
Fixes: bug #1049249

nova/cells/opts.py

@@ -43,6 +43,9 @@ cells_opts = [
                 default=10.0,
                 help='Percentage of cell capacity to hold in reserve. '
                      'Affects both memory and disk utilization'),
+    cfg.StrOpt('cell_type',
+                default=None,
+                help='Type of cell: api or compute'),
 ]
 
 cfg.CONF.register_opts(cells_opts, group='cells')

nova/compute/__init__.py

@@ -20,21 +20,65 @@ import oslo.config.cfg
 
 # Importing full names to not pollute the namespace and cause possible
 # collisions with use of 'from nova.compute import <foo>' elsewhere.
+import nova.exception
 import nova.openstack.common.importutils
+from nova.openstack.common import log as logging
+
+LOG = logging.getLogger(__name__)
 
 _compute_opts = [
     oslo.config.cfg.StrOpt('compute_api_class',
                            default='nova.compute.api.API',
                            help='The full class name of the '
-                                'compute API class to use'),
+                                'compute API class to use (deprecated)'),
 ]
-
 oslo.config.cfg.CONF.register_opts(_compute_opts)
 
+oslo.config.cfg.CONF.import_opt('enable',
+                            'nova.cells.opts',
+                            group='cells')
+
+oslo.config.cfg.CONF.import_opt('cell_type',
+                            'nova.cells.opts',
+                            group='cells')
+
+COMPUTE_API = 'nova.compute.api.API'
+COMPUTE_CELL_API = 'nova.compute.cells_api.ComputeCellsAPI'
+
+
+def get_compute_api_class_name():
+    """
+    Returns the name of compute API class.
+    """
+    if not oslo.config.cfg.CONF.cells.enable:
+        return COMPUTE_API
+
+    cell_type = oslo.config.cfg.CONF.cells.cell_type
+    # If cell is enabled and cell_type option is not set (and thus get the
+    # default value None), use the deprecated compute_api_class option.
+    if cell_type is None:
+        compute_api_class_name = oslo.config.cfg.CONF.compute_api_class
+        LOG.deprecated(_("The compute_api_class is now deprecated and "
+                         "will be removed in next release. Please set the"
+                         " cell_type option to api or compute"))
+    # If cell is enabled and this cell is an API-cell, use cell specific
+    # computeAPI.
+    elif cell_type == 'api':
+        compute_api_class_name = COMPUTE_CELL_API
+    # If cell is enabled and this cell is a COMPUTE-cell, use normal
+    # computeAPI.
+    elif cell_type == 'compute':
+        compute_api_class_name = COMPUTE_API
+    # Otherwise, raise exception for invalid cell_type
+    else:
+        msg = _("cell_type must be configured as 'api' or 'compute'")
+        raise nova.exception.InvalidInput(reason=msg)
+    return compute_api_class_name
+
 
 def API(*args, **kwargs):
     importutils = nova.openstack.common.importutils
-    class_name = oslo.config.cfg.CONF.compute_api_class
+    class_name = get_compute_api_class_name()
     return importutils.import_object(class_name, *args, **kwargs)
 
 
@@ -44,7 +88,7 @@ def HostAPI(*args, **kwargs):
     api
     """
     importutils = nova.openstack.common.importutils
-    compute_api_class_name = oslo.config.cfg.CONF.compute_api_class
+    compute_api_class_name = get_compute_api_class_name()
     compute_api_class = importutils.import_class(compute_api_class_name)
     class_name = compute_api_class.__module__ + ".HostAPI"
     return importutils.import_object(class_name, *args, **kwargs)
@@ -56,7 +100,7 @@ def InstanceActionAPI(*args, **kwargs):
     configured compute api.
     """
     importutils = nova.openstack.common.importutils
-    compute_api_class_name = oslo.config.cfg.CONF.compute_api_class
+    compute_api_class_name = get_compute_api_class_name()
     compute_api_class = importutils.import_class(compute_api_class_name)
     class_name = compute_api_class.__module__ + ".InstanceActionAPI"
     return importutils.import_object(class_name, *args, **kwargs)

nova/tests/compute/test_compute.py

@@ -9276,3 +9276,27 @@ class CheckRequestedImageTestCase(test.TestCase):
 
         self.compute_api._check_requested_image(self.context, image['id'],
                 image, self.instance_type)
+
+
+class ComputeAPIClassNameTestCase(test.TestCase):
+    def setUp(self):
+        super(ComputeAPIClassNameTestCase, self).setUp()
+
+    def test_default_compute_api_class_name(self):
+        result = compute.get_compute_api_class_name()
+        self.assertEqual('nova.compute.api.API', result)
+
+    def test_cell_compute_api_class_name(self):
+        self.flags(enable=True, group='cells')
+        self.flags(cell_type='api', group='cells')
+        result = compute.get_compute_api_class_name()
+        self.assertEqual('nova.compute.cells_api.ComputeCellsAPI', result)
+        self.flags(cell_type='compute', group='cells')
+        result = compute.get_compute_api_class_name()
+        self.assertEqual('nova.compute.api.API', result)
+
+    def test_illegal_cell_compute_api_class_name(self):
+        self.flags(enable=True, group='cells')
+        self.flags(cell_type='fake_cell_type', group='cells')
+        self.assertRaises(exception.InvalidInput,
+                          compute.get_compute_api_class_name)

nova/tests/compute/test_host_api.py

@@ -252,7 +252,8 @@ class ComputeHostAPITestCase(test.TestCase):
 
 class ComputeHostAPICellsTestCase(ComputeHostAPITestCase):
     def setUp(self):
-        self.flags(compute_api_class='nova.compute.cells_api.ComputeCellsAPI')
+        self.flags(enable=True, group='cells')
+        self.flags(cell_type='api', group='cells')
         super(ComputeHostAPICellsTestCase, self).setUp()
 
     def _mock_rpc_call(self, expected_message, result=None):