Drop support for custom schedulers

We deprecated this functionality in Ussuri and can now remove it. It's
highly unlikely that there exists a functioning alternative to this
scheduler and it's not something we can really support nowadays.

Change-Id: I546d3d329a69acaad3ada48ccbfddf3a274b6ce2
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

nova/cmd/scheduler.py

@@ -27,7 +27,7 @@ import nova.conf
 from nova.conf import remote_debug
 from nova import config
 from nova import objects
-from nova.scheduler import rpcapi as scheduler_rpcapi
+from nova.scheduler import rpcapi
 from nova import service
 from nova import version
 
@@ -44,13 +44,11 @@ def main():
 
     gmr.TextGuruMeditation.setup_autorun(version, conf=CONF)
 
-    server = service.Service.create(binary='nova-scheduler',
-                                    topic=scheduler_rpcapi.RPC_TOPIC)
+    server = service.Service.create(
+        binary='nova-scheduler', topic=rpcapi.RPC_TOPIC)
+
     # Determine the number of workers; if not specified in config, default
-    # to ncpu for the FilterScheduler and 1 for everything else.
-    workers = CONF.scheduler.workers
-    if not workers:
-        workers = (processutils.get_worker_count()
-                   if CONF.scheduler.driver == 'filter_scheduler' else 1)
+    # to number of CPUs
+    workers = CONF.scheduler.workers or processutils.get_worker_count()
     service.serve(server, workers=workers)
     service.wait()

nova/conf/scheduler.py

@@ -22,39 +22,6 @@ scheduler_group = cfg.OptGroup(name="scheduler",
                                title="Scheduler configuration")
 
 scheduler_opts = [
-    cfg.StrOpt("driver",
-        default="filter_scheduler",
-        deprecated_name="scheduler_driver",
-        deprecated_group="DEFAULT",
-        deprecated_for_removal=True,
-        deprecated_since='21.0.0',
-        deprecated_reason="""
-nova no longer provides any in-tree filters except for the 'filter_scheduler'
-scheduler. This filter is considered flexible and pluggable enough for all use
-cases and can be extended through the use of custom, out-of-tree filters and
-weighers along with powerful, in-tree filters like the
-'AggregateInstanceExtraSpecsFilter' and 'ComputeCapabilitiesFilter' filters.
-""",
-        help="""
-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.
-
-Possible values:
-
-* Any of the drivers included in Nova:
-
-  * filter_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.
-
-Related options:
-
-* workers
-"""),
     cfg.IntOpt("periodic_task_interval",
         default=60,
         help="""

nova/scheduler/manager.py

@@ -25,7 +25,6 @@ from oslo_log import log as logging
 import oslo_messaging as messaging
 from oslo_serialization import jsonutils
 from oslo_service import periodic_task
-from stevedore import driver
 
 import nova.conf
 from nova import exception
@@ -34,6 +33,7 @@ from nova import objects
 from nova.objects import host_mapping as host_mapping_obj
 from nova import quota
 from nova.scheduler.client import report
+from nova.scheduler import filter_scheduler
 from nova.scheduler import request_filter
 from nova.scheduler import utils
 
@@ -56,11 +56,7 @@ class SchedulerManager(manager.Manager):
 
     def __init__(self, *args, **kwargs):
         self.placement_client = report.SchedulerReportClient()
-        self.driver = driver.DriverManager(
-            'nova.scheduler.driver',
-            CONF.scheduler.driver,
-            invoke_on_load=True
-        ).driver
+        self.driver = filter_scheduler.FilterScheduler()
 
         super(SchedulerManager, self).__init__(
             service_name='scheduler', *args, **kwargs

nova/tests/functional/libvirt/base.py

@@ -99,7 +99,6 @@ class ServersTestBase(integrated_helpers._IntegratedTestBase):
         enabled_filters = CONF.filter_scheduler.enabled_filters
         enabled_filters += self.ADDITIONAL_FILTERS
 
-        self.flags(driver='filter_scheduler', group='scheduler')
         self.flags(enabled_filters=enabled_filters, group='filter_scheduler')
 
         return self.start_service('scheduler')

nova/tests/unit/scheduler/test_manager.py

@@ -44,16 +44,6 @@ class SchedulerManagerInitTestCase(test.NoDBTestCase):
         driver = self.manager_cls().driver
         self.assertIsInstance(driver, filter_scheduler.FilterScheduler)
 
-    @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/remove-customer-filters-95ab8c7a3aff058d.yaml

@@ -0,0 +1,11 @@
+---
+upgrade:
+  - |
+    Support for custom scheduler drivers, deprecated since the 21.0.0 (Ussuri)
+    release, has been removed. The default ``filter_scheduler`` is now
+    considered performant enough to suit all use cases. Users with specific
+    requirements that they feel are not met by the filter scheduler should
+    contact the nova developers to discuss their issue.
+  - |
+    The ``[scheduler] scheduler_driver`` config option has been removed, along
+    with the ``nova.scheduler.driver`` setuptools entrypoint.

setup.cfg

@@ -64,8 +64,6 @@ nova.api.extra_spec_validators =
     vmware = nova.api.validation.extra_specs.vmware
 nova.compute.monitors.cpu =
     virt_driver = nova.compute.monitors.cpu.virt_driver:Monitor
-nova.scheduler.driver =
-    filter_scheduler = nova.scheduler.filter_scheduler:FilterScheduler
 console_scripts =
     nova-api = nova.cmd.api:main
     nova-api-metadata = nova.cmd.api_metadata:main