Deprecate the IronicHostManager

The use_baremetal_filters and baremetal_enabled_filters options
along with the ExactRamFilter, ExactCoreFilter and ExactDiskFilter
filters were all deprecated in Pike:

  I843353427c90142a366ae9ca63ee4298b4f3ecd4

The IronicHostManager is configurable and relies on those options,
so if those options are deprecated then the IronicHostManager should
also be deprecated.

The sticky part with this is going to be filters that don't work with
ironic nodes today, like the NUMATopologyFilter, so a note is left
in the use_baremetal_filters option code to remind us that we can't
likely remove any of this until all filters work with ironic nodes.

Change-Id: Iebc74a09990dcda8cf0ee2a41f9ae1058d2a182a

nova/conf/scheduler.py

@@ -31,6 +31,9 @@ The scheduler host manager to use.
 The host manager manages the in-memory picture of the hosts that the scheduler
 uses. The options values are chosen from the entry points under the namespace
 'nova.scheduler.host_manager' in 'setup.cfg'.
+
+NOTE: The "ironic_host_manager" option is deprecated as of the 17.0.0 Queens
+release.
 """),
     cfg.StrOpt("driver",
         default="filter_scheduler",
@@ -320,6 +323,10 @@ Related options:
     cfg.BoolOpt("use_baremetal_filters",
         deprecated_name="scheduler_use_baremetal_filters",
         deprecated_group="DEFAULT",
+        # NOTE(mriedem): We likely can't remove this option until the
+        # IronicHostManager is removed, and we likely can't remove that
+        # until all filters can at least not fail on ironic nodes, like the
+        # NUMATopologyFilter.
         deprecated_for_removal=True,
         deprecated_reason="""
 These filters were used to overcome some of the baremetal scheduling

nova/scheduler/ironic_host_manager.py

@@ -22,6 +22,7 @@ ram from a host / node as it is supporting Baremetal hosts, which can not be
 subdivided into multiple instances.
 """
 from oslo_log import log as logging
+from oslo_log import versionutils
 
 import nova.conf
 from nova import context as context_module
@@ -88,6 +89,13 @@ class IronicNodeState(host_manager.HostState):
 class IronicHostManager(host_manager.HostManager):
     """Ironic HostManager class."""
 
+    def __init__(self):
+        super(IronicHostManager, self).__init__()
+        msg = ('The IronicHostManager is deprecated and may be removed as '
+               'early as the 18.0.0 Rocky release. Deployments need to '
+               'schedule based on resource classes.')
+        versionutils.report_deprecated_feature(LOG, msg)
+
     @staticmethod
     def _is_ironic_compute(compute):
         ht = compute.hypervisor_type if 'hypervisor_type' in compute else None

releasenotes/notes/deprecate-ironic-host-manager-bacb8d7b1e318e37.yaml

@@ -0,0 +1,14 @@
+---
+deprecations:
+  - |
+    The `IronicHostManager` is now deprecated along with the
+    ``[scheduler]/host_manager`` option of ``ironic_host_manager``.
+
+    As of the 16.0.0 Pike release, the ``ExactRamFilter``, ``ExactCoreFilter``,
+    and ``ExactDiskFilter`` scheduler filters are all deprecated along with
+    the ``[scheduler]/use_baremetal_filters`` and
+    ``[scheduler]/baremental_enabled_filters`` options. Deployments should
+    migrate to using resource classes with baremetal flavors as described in
+    the ironic install guide:
+
+    https://docs.openstack.org/ironic/latest/install/configure-nova-flavors.html#scheduling-based-on-resource-classes

setup.cfg

@@ -83,6 +83,7 @@ nova.ipv6_backend =
 
 nova.scheduler.host_manager =
     host_manager = nova.scheduler.host_manager:HostManager
+    # Deprecated starting from the 17.0.0 Queens release.
     ironic_host_manager = nova.scheduler.ironic_host_manager:IronicHostManager
 
 nova.scheduler.driver =