Ensure the components are isolated from the system

This creates a specific slice which all OpenStack services will operate
from. By creating an independent slice these components will be governed
away from the system slice allowing us to better optimise resource
consumption.

See the following for more information on slices:

* https://www.freedesktop.org/software/systemd/man/systemd.slice.html

See for following for more information on resource controls:

* https://www.freedesktop.org/software/systemd/man/systemd.resource-control.html

Tools like ``systemd-cgtop`` and ``systemd-cgls`` will now give us
insight into specific processes, process groups, and resouce consumption
in ways that we've not had access to before. To enable some of this reporting
the accounting options have been added to the [Service] section of the unit
file.

Change-Id: I3cdaf5829011b5b73112e1a76a6dfc7259b169f5
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

defaults/main.yml

@@ -418,37 +418,56 @@ nova_libvirtd_listen_tcp: 0
 nova_libvirtd_auth_tcp: sasl
 nova_libvirtd_debug_log_filters: "3:remote 4:event 3:json 3:rpc"
 
+nova_api_metadata_init_overrides: {}
+nova_api_os_compute_init_overrides: {}
+nova_compute_init_overrides: {}
+nova_conductor_init_overrides: {}
+nova_consoleauth_init_overrides: {}
+nova_novncproxy_init_overrides: {}
+nova_scheduler_init_overrides: {}
+nova_spicehtml5proxy_init_overrides: {}
+nova_placement_api_init_overrides: {}
+
 ## Service Name-Group Mapping
 nova_services:
   nova-api-metadata:
     group: nova_api_metadata
     service_name: nova-api-metadata
+    init_config_overrides: "{{ nova_api_metadata_init_overrides }}"
   nova-api-os-compute:
     group: nova_api_os_compute
     service_name: nova-api-os-compute
+    init_config_overrides: "{{ nova_api_os_compute_init_overrides }}"
   nova-compute:
     group: nova_compute
     service_name: nova-compute
+    init_config_overrides: "{{ nova_compute_init_overrides }}"
   nova-conductor:
     group: nova_conductor
     service_name: nova-conductor
+    init_config_overrides: "{{ nova_conductor_init_overrides }}"
   nova-consoleauth:
     group: nova_console
     service_name: nova-consoleauth
+    init_config_overrides: "{{ nova_consoleauth_init_overrides }}"
   nova-novncproxy:
     group: nova_console
     service_name: nova-novncproxy
+    init_config_overrides: "{{ nova_novncproxy_init_overrides }}"
     condition: "{{ nova_console_type == 'novnc' }}"
   nova-scheduler:
     group: nova_scheduler
     service_name: nova-scheduler
+    init_config_overrides: "{{ nova_scheduler_init_overrides }}"
   nova-spicehtml5proxy:
     group: nova_console
     service_name: nova-spicehtml5proxy
+    init_config_overrides: "{{ nova_spicehtml5proxy_init_overrides }}"
     condition: "{{ nova_console_type == 'spice' }}"
   nova-placement-api:
     group: nova_api_placement
     service_name: nova-placement-api
+    init_config_overrides: "{{ nova_placement_api_init_overrides }}"
     condition: "{{ nova_placement_service_enabled | bool }}"
     log_string: "--logto "
     program_override: "{{ nova_bin }}/uwsgi --ini /etc/uwsgi/nova-placement-uwsgi.ini"

releasenotes/notes/nova-init-config-overrides-ffce7e419061c4da.yaml

@@ -0,0 +1,9 @@
+---
+features:
+  - New variables have been added to allow a deployer to customize
+    a nova systemd unit file to their liking.
+  - The task dropping the nova systemd unit files now uses the
+    ``config_template`` action plugin allowing deployers access to
+    customize the unit files as they see fit without having to
+    load extra options into the defaults and polute the generic
+    systemd unit file with jinja2 variables and conditionals.

tasks/nova_init_systemd.yml

@@ -62,12 +62,14 @@
     - "{{ item.value.condition | default(true) }}"
 
 - name: Place the systemd init script
-  template:
+  config_template:
     src: "nova-systemd-init.j2"
     dest: "/etc/systemd/system/{{ item.value.service_name }}.service"
     mode: "0644"
     owner: "root"
     group: "root"
+    config_overrides: "{{ item.value.init_config_overrides }}"
+    config_type: "ini"
   with_dict: "{{ nova_services }}"
   when:
     - inventory_hostname in groups[item.value.group]

templates/nova-systemd-init.j2

@@ -21,5 +21,14 @@ TimeoutSec=300
 Restart=on-failure
 RestartSec=150
 
+# This creates a specific slice which all nova services will operate from
+#  The accounting options give us the ability to see resource usage through
+#  the `systemd-cgtop` command.
+Slice=nova.slice
+CPUAccounting=true
+BlockIOAccounting=true
+MemoryAccounting=false
+TasksAccounting=true
+
 [Install]
 WantedBy=multi-user.target