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: Ic4edfa39b8ee42d0f6192b986e1c40c9c94488df
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>
(cherry picked from commit 012d3f3530)

defaults/main.yml

@@ -163,14 +163,19 @@ sahara_pip_packages:
   - python-keystoneclient
   - warlock
 
+sahara_engine_init_overrides: {}
+sahara_api_init_overrides: {}
+
 ## Service Names
 sahara_services:
   sahara-api:
     group: sahara_api
     service_name: sahara-api
+    init_config_overrides: "{{ sahara_api_init_overrides }}"
   sahara-engine:
     group: sahara_engine
     service_name: sahara-engine
+    init_config_overrides: "{{ sahara_engine_init_overrides }}"
 
 # This variable is used by the repo_build process to determine
 # which host group to check for members of before building the

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

@@ -0,0 +1,10 @@
+---
+features:
+  - New variables have been added to allow a deployer to customize
+    a sahara systemd unit file to their liking.
+  - The task dropping the sahara 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/sahara_init_systemd.yml

@@ -54,12 +54,14 @@
   when: inventory_hostname in groups[item.value.group]
 
 - name: Place the systemd init script
-  template:
+  config_template:
     src: "sahara-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: "{{ sahara_services }}"
   when: inventory_hostname in groups[item.value.group]
   notify:

templates/sahara-systemd-init.j2

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