Merge "Accept any scheduler driver entrypoint"

nova/conf/scheduler.py

@@ -34,25 +34,32 @@ uses. The options values are chosen from the entry points under the namespace
 """),
     cfg.StrOpt("driver",
         default="filter_scheduler",
-        choices=("filter_scheduler", "caching_scheduler",
-                 "chance_scheduler", "fake_scheduler"),
         deprecated_name="scheduler_driver",
         deprecated_group="DEFAULT",
         help="""
-The class of the driver used by the scheduler.
+The class of the driver used by the scheduler. This should be chosen from one
+of the entrypoints under the namespace 'nova.scheduler.driver' of file
+'setup.cfg'. If nothing is specified in this option, the 'filter_scheduler' is
+used.
 
-The options are chosen from the entry points under the namespace
-'nova.scheduler.driver' in 'setup.cfg'.
+Other options are:
+
+* 'caching_scheduler' which aggressively caches the system state for better
+  individual scheduler performance at the risk of more retries when running
+  multiple schedulers.
+* 'chance_scheduler' which simply picks a host at random.
+* 'fake_scheduler' which is used for testing.
 
 Possible values:
 
-* A string, where the string corresponds to the class name of a scheduler
-  driver. There are a number of options available:
-** 'caching_scheduler', which aggressively caches the system state for better
-   individual scheduler performance at the risk of more retries when running
-   multiple schedulers
-** 'chance_scheduler', which simply picks a host at random
-** 'fake_scheduler', which is used for testing
+* Any of the drivers included in Nova:
+** filter_scheduler
+** caching_scheduler
+** chance_scheduler
+** fake_scheduler
+* You may also set this to the entry point name of a custom scheduler driver,
+  but you will be responsible for creating and maintaining it in your setup.cfg
+  file.
 """),
     cfg.IntOpt("periodic_task_interval",
         default=60,

nova/tests/unit/scheduler/test_scheduler.py

@@ -67,6 +67,16 @@ class SchedulerManagerInitTestCase(test.NoDBTestCase):
         driver = self.manager_cls().driver
         self.assertIsInstance(driver, caching_scheduler.CachingScheduler)
 
+    @mock.patch.object(host_manager.HostManager, '_init_instance_info')
+    @mock.patch.object(host_manager.HostManager, '_init_aggregates')
+    def test_init_nonexist_schedulerdriver(self,
+                                           mock_init_agg,
+                                           mock_init_inst):
+        self.flags(driver='nonexist_scheduler', group='scheduler')
+        # The entry point has to be defined in setup.cfg and nova-scheduler has
+        # to be deployed again before using a custom value.
+        self.assertRaises(RuntimeError, self.manager_cls)
+
 
 class SchedulerManagerTestCase(test.NoDBTestCase):
     """Test case for scheduler manager."""

releasenotes/notes/bug-1704788-490797827bae9142.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - Correctly allow the use of a custom scheduler driver by using the name of
+    the custom driver entry point in the ``[scheduler]/driver`` config option.
+    You must also update the entry point in ``setup.cfg``.