Mark Goddard af3b719b73 Move group_vars to an inventory directory

The group variables originally in ansible/group_vars/ were playbook
group variables, due to being adjacent to the playbooks. Typically they
provided default values for global variables in the all group, as well
as some more specific groups. This has worked fairly well, but results
in (at least) a couple of problems.

1. The default variable precedence rules mean that these playbook group
   variables have a higher precedence than inventory group variables
   (for a given group). This can make it challenging to override
   playbook group variables in the inventory in Kayobe configuration.

2. Any playbook run by Kayobe must be in the same directory as the
   playbook group variables in order to use them. Given that they
   include variables required for connectivity such as ansible_host and
   ansible_user, this is quite critical. For Kayobe custom playbooks, we
   work around this by symlinking to the group_vars directory from the
   directory containing the custom playbook. This is not an elegant
   workaround, and has assumptions about the relative paths of the
   Kayobe configuration and virtual environment in which Kayobe is
   installed.

Story: 2010280
Task: 46233

Change-Id: Ifea5c7e73f6f410f96a7398bfd349d1f631d9fc0

2022-09-08 10:11:23 +01:00

6.1 KiB

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Kayobe Configuration

This section covers configuration of Kayobe. As an Ansible-based project, Kayobe is for the most part configured using YAML files.

Configuration Location

Kayobe configuration is by default located in /etc/kayobe on the Ansible control host. This location can be overridden to a different location to avoid touching the system configuration directory by setting the environment variable KAYOBE_CONFIG_PATH. Similarly, kolla configuration on the Ansible control host will by default be located in /etc/kolla and can be overridden via KOLLA_CONFIG_PATH.

Configuration Directory Layout

The Kayobe configuration directory contains Ansible extra-vars files and the Ansible inventory. An example of the directory structure is as follows:

extra-vars1.yml
extra-vars2.yml
inventory/
    group_vars/
        group1-vars
        group2-vars
    groups
    host_vars/
        host1-vars
        host2-vars
    hosts

Configuration Patterns

Ansible's variable precedence rules are fairly well documented and provide a mechanism we can use for providing site localisation and customisation of OpenStack in combination with some reasonable default values. For global configuration options, Kayobe typically uses the following patterns:

Inventory group variables for the all group in <kayobe repo>/ansible/inventory/group_vars/all/* set global defaults. These files should not be modified.
Inventory group variables for other groups in <kayobe repo>/ansible/inventory/group_vars/<group>/* set defaults for some subsets of hosts. These files should not be modified.
Extra-vars files in ${KAYOBE_CONFIG_PATH}/*.yml set custom values for global variables and should be used to apply global site localisation and customisation. By default these variables are commented out.

Additionally, variables can be set on a per-group or per-host basis using inventory group or host variables files in ${KAYOBE_CONFIG_PATH}/inventory/group_vars/* or ${KAYOBE_CONFIG_PATH}/inventory/host_vars/* respectively. It should be noted that variables set in extra-vars files take precedence over per-host variables.

Configuring Kayobe

The kayobe-config git repository contains a Kayobe configuration directory structure and unmodified configuration files. This repository can be used as a mechanism for version controlling Kayobe configuration. As Kayobe is updated, the configuration should be merged to incorporate any upstream changes with local modifications.

Alternatively, the baseline Kayobe configuration may be copied from a checkout of the Kayobe repository to the Kayobe configuration path:

$ mkdir -p ${KAYOBE_CONFIG_PATH:-/etc/kayobe/}
$ cp -r etc/kayobe/* ${KAYOBE_CONFIG_PATH:-/etc/kayobe/}

Once in place, each of the YAML and inventory files should be manually inspected and configured as required.

Inventory

The inventory should contain the following hosts:

Ansible Control host: This should be localhost.
Seed hypervisor: If provisioning a seed VM, a host should exist for the hypervisor that will run the VM, and should be a member of the seed-hypervisor group.
Seed: The seed host, whether provisioned as a VM by Kayobe or externally managed, should exist in the seed group.

Cloud hosts and bare metal compute hosts are not required to exist in the inventory if discovery of the control plane hardware is planned, although entries for groups may still be required.

Use of advanced control planes with multiple server roles and customised service placement across those servers is covered in control-plane-service-placement.

Site Localisation and Customisation

Site localisation and customisation is applied using Ansible extra-vars files in ${KAYOBE_CONFIG_PATH}/*.yml.

Configuration of Ansible

Ansible configuration is described in detail in the Ansible documentation. In addition to the standard locations, Kayobe supports using an Ansible configuration file located in the Kayobe configuration at ${KAYOBE_CONFIG_PATH}/ansible.cfg. Note that if the ANSIBLE_CONFIG environment variable is specified it takes precedence over this file.

Encryption of Secrets

Kayobe supports the use of Ansible vault to encrypt sensitive information in its configuration. The ansible-vault tool should be used to manage individual files for which encryption is required. Any of the configuration files may be encrypted. Since encryption can make working with Kayobe difficult, it is recommended to follow best practice, adding a layer of indirection and using encryption only where necessary.

Location of data files

Kayobe needs to know where to find any files not contained within its python package; this includes its Ansible playbooks and any other files it needs for runtime operation. These files are known collectively as 'data files'.

Kayobe will attempt to detect the location of its data files automatically. However, if you have installed kayobe to a non-standard location this auto-detection may fail. It is possible to manually override the path using the environment variable: KAYOBE_DATA_FILES_PATH. This should be set to a path with the following structure:

requirements.yml
ansible/
    roles/
        ...
    ...

Where ansible is the ansible directory from the source checkout and ... is an elided representation of any files and subdirectories contained within that directory.

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