.. _control-plane-service-placement:
===============================
Control Plane Service Placement
===============================
.. note::
This is an advanced topic and should only be attempted when familiar with
kayobe and OpenStack.
The default configuration in kayobe places all control plane services on a
single set of servers described as 'controllers'. In some cases it may be
necessary to introduce more than one server role into the control plane, and
control which services are placed onto the different server roles.
Configuration
=============
Overcloud Inventory Discovery
-----------------------------
If using a seed host to enable discovery of the control plane services, it is
necessary to configure how the discovered hosts map into kayobe groups. This
is done using the ``overcloud_group_hosts_map`` variable, which maps names of
kayobe groups to a list of the hosts to be added to that group.
This variable will be used during the command ``kayobe overcloud inventory
discover``. An inventory file will be generated in
``${KAYOBE_CONFIG_PATH}/inventory/overcloud`` with discovered hosts added to
appropriate kayobe groups based on ``overcloud_group_hosts_map``.
Kolla-ansible Inventory Mapping
-------------------------------
Once hosts have been discovered and enrolled into the kayobe inventory, they
must be added to the kolla-ansible inventory. This is done by mapping from top
level kayobe groups to top level kolla-ansible groups using the
``kolla_overcloud_inventory_top_level_group_map`` variable. This variable maps
from kolla-ansible groups to lists of kayobe groups, and variables to define
for those groups in the kolla-ansible inventory.
Variables For Custom Server Roles
---------------------------------
Certain variables must be defined for hosts in the ``overcloud`` group. For
hosts in the ``controllers`` group, many variables are mapped to other
variables with a ``controller_`` prefix in files under
``ansible/group_vars/controllers/``. This is done in order that they may be set
in a global extra variables file, typically ``controllers.yml``, with defaults
set in ``ansible/group_vars/all/controllers``. A similar scheme is used for
hosts in the ``monitoring`` group.
.. table:: Overcloud host variables
====================== =====================================================
Variable Purpose
====================== =====================================================
``ansible_user`` Username with which to access the host via SSH.
``bootstrap_user`` Username with which to access the host before
``ansible_user`` is configured.
``lvm_groups`` List of LVM volume groups to configure. See
`mrlesmithjr.manage-lvm role
`_
for format.
``network_interfaces`` List of names of networks to which the host is
connected.
``sysctl_parameters`` Dict of sysctl parameters to set.
====================== =====================================================
If configuring BIOS and RAID via ``kayobe overcloud bios raid configure``, the
following variables should also be defined:
.. table:: Overcloud BIOS & RAID host variables
====================== =====================================================
Variable Purpose
====================== =====================================================
``bios_config`` Dict mapping BIOS configuration options to their
required values. See `stackhpc.drac role
`_ for
format.
``raid_config`` List of RAID virtual disks to configure. See
`stackhpc.drac role
`_ for
format.
====================== =====================================================
These variables can be defined in inventory host or group variables files,
under ``${KAYOBE_CONFIG_PATH}/inventory/host_vars/`` or
``${KAYOBE_CONFIG_PATH}/inventory/group_vars/`` respectively.
Custom Kolla-ansible Inventories
--------------------------------
As an advanced option, it is possible to fully customise the content of the
kolla-ansible inventory, at various levels. To facilitate this, kayobe breaks
the kolla-ansible inventory into three separate sections.
**Top level** groups define the roles of hosts, e.g. ``controller`` or ``compute``,
and it is to these groups that hosts are mapped directly.
**Components** define groups of services, e.g. ``nova`` or ``ironic``, which
are mapped to top level groups.
**Services** define single containers, e.g. ``nova-compute`` or ``ironic-api``,
which are mapped to components.
The default top level inventory is generated from
``kolla_overcloud_inventory_top_level_group_map``.
Kayobe's component- and service-level inventory for
kolla-ansible is static, and taken from the kolla-ansible example ``multinode``
inventory. The complete inventory is generated by concatenating these
inventories.
Each level may be separately overridden by setting the following variables:
.. table:: Custom kolla-ansible inventory variables
=============================================== =================================
Variable Purpose
=============================================== =================================
``kolla_overcloud_inventory_custom_top_level`` Overcloud inventory containing a
mapping from top level groups
to hosts.
``kolla_overcloud_inventory_custom_components`` Overcloud inventory
containing a mapping from
components to top level
groups.
``kolla_overcloud_inventory_custom_services`` Overcloud inventory
containing a mapping from
services to components.
``kolla_overcloud_inventory_custom`` Full overcloud inventory
contents.
=============================================== =================================
Examples
========
Example 1: Adding Network Hosts
-------------------------------
This example walks through the configuration that could be applied to enable
the use of separate hosts for neutron network services and load balancing.
The control plane consists of three controllers, ``controller-[0-2]``, and two
network hosts, ``network-[0-1]``. All file paths are relative to
``${KAYOBE_CONFIG_PATH}``.
First, we must map the hosts to kayobe groups.
.. code-block:: yaml
:caption: ``overcloud.yml``
overcloud_group_hosts_map:
controllers:
- controller-0
- controller-1
- controller-2
network:
- network-0
- network-1
Next, we must map these groups to kolla-ansible groups.
.. code-block:: yaml
:caption: ``kolla.yml``
kolla_overcloud_inventory_top_level_group_map:
control:
groups:
- controllers
network:
groups:
- network
Finally, we create a group variables file for hosts in the network group,
providing the necessary variables for a control plane host.
.. code-block:: yaml
:caption: ``inventory/group_vars/network``
ansible_user: "{{ kayobe_ansible_user }}"
bootstrap_user: "{{ controller_bootstrap_user }}"
lvm_groups: "{{ controller_lvm_groups }}"
network_interfaces: "{{ controller_network_host_network_interfaces }}"
sysctl_parameters: "{{ controller_sysctl_parameters }}"
Here we are using the controller-specific values for some of these variables,
but they could equally be different.
Example 2: Overriding the Kolla-ansible Inventory
-------------------------------------------------
This example shows how to override one or more sections of the kolla-ansible
inventory. All file paths are relative to ``${KAYOBE_CONFIG_PATH}``.
First, create a file containing the customised inventory section. We'll use the
**components** section in this example.
.. code-block:: console
:caption: ``kolla/inventory/overcloud-components.j2``
[nova]
control
[ironic]
{% if kolla_enable_ironic | bool %}
control
{% endif %}
...
Next, we must configure kayobe to use this inventory template.
.. code-block:: yaml
:caption: ``kolla.yml``
kolla_overcloud_inventory_custom_components: "{{ lookup('template', kayobe_config_path ~ '/kolla/inventory/overcloud-components.j2') }}"
Here we use the ``template`` lookup plugin to render the Jinja2-formatted
inventory template.