Add a variable to configure which hosts run nova compute for ironic

May be used to avoid HA nova compute for ironic, which is experimental.

ansible/group_vars/all/nova

+---
+###############################################################################
+# Nova configuration.
+
+# Which group to use to deploy the nova-compute services for ironic. By default
+# all hosts in the nova group are used - typically the controllers.
+kolla_nova_compute_ironic_group: nova

ansible/roles/kolla-ansible/defaults/main.yml

@@ -205,6 +205,17 @@ kolla_openstack_logging_debug:
 #kolla_enable_tempest:
 #kolla_enable_watcher:
 
+#######################
+# Nova options
+#######################
+
+# Which group to use to deploy the nova-compute services for ironic. By default
+# all hosts in the nova group are used - typically the controllers.
+kolla_nova_compute_ironic_group: nova
+
+###############################################################################
+# Extra free-form configuraton.
+
 # Free form extra configuration to append to {{ kolla_config_path }}/globals.yml.
 kolla_extra_globals:
 

ansible/roles/kolla-ansible/templates/overcloud-services.j2

@@ -38,7 +38,10 @@ nova
 nova
 
 [nova-compute-ironic:children]
-nova
+# NOTE: HA for nova-compute services with ironic is still an experimental
+# feature. Provide the option to use a single compute host, even when multiple
+# controllers are in use.
+{{ kolla_nova_compute_ironic_group }}
 
 [nova-serialproxy:children]
 nova

doc/source/release-notes.rst

@@ -20,6 +20,10 @@ Features
 * Adds support for specifying a local Yum mirror for package installation.
 * Adds the command ``kayobe network connectivity check`` which can be used to
   verify network connectivity in the cloud hosts.
+* Adds a variable ``kolla_nova_compute_ironic_group`` which may be used to set
+  which hosts run the nova compute service for ironic. This may be used to
+  avoid the experimental HA nova compute service for ironic, by specifying a
+  single host.
 
 Upgrade Notes
 -------------

etc/kayobe/nova.yml

+---
+###############################################################################
+# Nova configuration.
+
+# Which group to use to deploy the nova-compute services for ironic. By default
+# all hosts in the nova group are used - typically the controllers.
+#kolla_nova_compute_ironic_group:
+
+###############################################################################
+# Dummy variable to allow Ansible to accept this file.
+workaround_ansible_issue_8743: yes