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Overriding default configuration

Variable precedence

Role defaults

Every role has a file, defaults/main.yml which holds the usual variables overridable by a deployer, like a regular Ansible role. This defaults are the closest possible to OpenStack standards.

They can be overridden at multiple levels.

Group vars and host vars

OpenStack-Ansible provides safe defaults for deployers in its group_vars folder. They take care of the wiring between different roles, like for example storing information on how to reach RabbitMQ from nova role.

You can override the existing group vars (and host vars) by creating your own folder in /etc/openstack_deploy/group_vars (and /etc/openstack_deploy/host_vars respectively).

If you want to change the location of the override folder, you can adapt your openstack-ansible.rc file, or export GROUP_VARS_PATH and HOST_VARS_PATH during your shell session.

Role vars

Every role makes use of additional variables in vars/ which take precedence over group vars.

These variables are typically internal to the role and are not designed to be overridden. However, deployers may choose to override them using extra-vars by placing the overrides into the user variables file.

User variables

If you want to globally override variable, you can define the variable you want to override in a /etc/openstack_deploy/user_*.yml file. It will apply on all hosts.

user_*.yml files in more details

Files in /etc/openstack_deploy beginning with user_ will be automatically sourced in any openstack-ansible command. Alternatively, the files can be sourced with the -e parameter of the ansible-playbook command.

user_variables.yml and user_secrets.yml are used directly by OpenStack-Ansible. Adding custom variables used by your own roles and playbooks to these files is not recommended. Doing so will complicate your upgrade path by making comparison of your existing files with later versions of these files more arduous. Rather, recommended practice is to place your own variables in files named following the user_*.yml pattern so they will be sourced alongside those used exclusively by OpenStack-Ansible.

user_*.yml files contain YAML variables which are applied as extra-vars when executing openstack-ansible to run playbooks. They will be sourced in alphanumeric order by openstack-ansible. If duplicate variables occur in the user_*.yml files, the variable in the last file read will take precedence.

Setting overrides in configuration files with config_template

All of the services that use YAML, JSON, or INI for configuration can receive overrides through the use of a Ansible action plugin named config_template. The configuration template engine allows a deployer to use a simple dictionary to modify or add items into configuration files at run time that may not have a preset template option. All OpenStack-Ansible roles allow for this functionality where applicable. Files available to receive overrides can be seen in the defaults/main.yml file as standard empty dictionaries (hashes).

This module was not accepted into Ansible Core (see PR1 and PR2), and will never be.

config_template documentation

These are the options available as found within the virtual module documentation section.

module: config_template
version_added: 1.9.2
short_description: >
  Renders template files providing a create/update override interface
description:
  - The module contains the template functionality with the ability to
    override items in config, in transit, through the use of a simple
    dictionary without having to write out various temp files on target
    machines. The module renders all of the potential jinja a user could
    provide in both the template file and in the override dictionary which
    is ideal for deployers who may have lots of different configs using a
    similar code base.
  - The module is an extension of the **copy** module and all of attributes
    that can be set there are available to be set here.
options:
  src:
    description:
      - Path of a Jinja2 formatted template on the local server. This can
        be a relative or absolute path.
    required: true
    default: null
  dest:
    description:
      - Location to render the template to on the remote machine.
    required: true
    default: null
  config_overrides:
    description:
      - A dictionary used to update or override items within a configuration
        template. The dictionary data structure may be nested. If the target
        config file is an ini file the nested keys in the ``config_overrides``
        will be used as section headers.
  config_type:
    description:
      - A string value describing the target config type.
    choices:
      - ini
      - json
      - yaml

Example task using the config_template module

In this task the test.ini.j2 file is a template which will be rendered and written to disk at /tmp/test.ini. The config_overrides entry is a dictionary (hash) which allows a deployer to set arbitrary data as overrides to be written into the configuration file at run time. The config_type entry specifies the type of configuration file the module will be interacting with; available options are « yaml », « json », and « ini ».

- name: Run config template ini
  config_template:
    src: test.ini.j2
    dest: /tmp/test.ini
    config_overrides: "{{ test_overrides }}"
    config_type: ini

Here is an example override dictionary (hash)

test_overrides:
  DEFAULT:
    new_item: 12345

And here is the template file:

[DEFAULT]
value1 = abc
value2 = 123

The rendered file on disk, namely /tmp/test.ini looks like this:

[DEFAULT]
value1 = abc
value2 = 123
new_item = 12345

Discovering available overrides

All of these options can be specified in any way that suits your deployment. In terms of ease of use and flexibility it’s recommended that you define your overrides in a user variable file such as /etc/openstack_deploy/user_variables.yml.

The list of overrides available may be found by executing:

ls /etc/ansible/roles/*/defaults/main.yml -1 \
    | xargs -I {} grep '_.*_overrides:' {} \
    | egrep -v "^#|^\s" \
    | sort -u

Note

Possible additional overrides can be found in the « Tunable Section » of each role’s main.yml file, such as /etc/ansible/roles/role_name/defaults/main.yml.

Overriding OpenStack configuration defaults

OpenStack has many configuration options available in .conf files (in a standard INI file format), policy files (in a standard JSON format) and YAML files, and can therefore use the config_template module described above.

OpenStack-Ansible enables you to reference any options in the OpenStack Configuration Reference through the use of a simple set of configuration entries in the /etc/openstack_deploy/user_variables.yml.

Overriding .conf files

Most often, overrides are implemented for the <service>.conf files (for example, nova.conf). These files use a standard INI file format.

For example, you might want to add the following parameters to the nova.conf file:

[DEFAULT]
remove_unused_original_minimum_age_seconds = 43200

[libvirt]
cpu_mode = host-model
disk_cachemodes = file=directsync,block=none

[database]
idle_timeout = 300
max_pool_size = 10

To do this, you use the following configuration entry in the /etc/openstack_deploy/user_variables.yml file:

nova_nova_conf_overrides:
  DEFAULT:
    remove_unused_original_minimum_age_seconds: 43200
  libvirt:
    cpu_mode: host-model
    disk_cachemodes: file=directsync,block=none
  database:
    idle_timeout: 300
    max_pool_size: 10

Note

The general format for the variable names used for overrides is <service>_<filename>_<file extension>_overrides. For example, the variable name used in these examples to add parameters to the nova.conf file is nova_nova_conf_overrides.

The same way you can apply overrides to the uwsgi services. For example:

nova_api_os_compute_uwsgi_ini_overrides:
  uwsgi:
    limit: 1024

Note

Some roles, like uwsgi, are used for lot of roles, and have « special » overrides, (like uwsgi_ini_overrides) which can be defined to impact all services which are using uwsgi. These variables are « special » as they will have precedence over role defined *_uwsgi_ini_overrides.

You can also apply overrides on a per-host basis with the following configuration in the /etc/openstack_deploy/openstack_user_config.yml file:

compute_hosts:
  900089-compute001:
    ip: 192.0.2.10
    host_vars:
      nova_nova_conf_overrides:
        DEFAULT:
          remove_unused_original_minimum_age_seconds: 43200
        libvirt:
          cpu_mode: host-model
          disk_cachemodes: file=directsync,block=none
        database:
          idle_timeout: 300
          max_pool_size: 10

Use this method for any files with the INI format for in OpenStack projects deployed in OpenStack-Ansible.

Overriding .json files

To implement access controls that are different from the ones in a standard OpenStack environment, you can adjust the default policies applied by services. Policy files are in a JSON format.

For example, you might want to add the following policy in the policy.json file for the Identity service (keystone):

{
    "identity:foo": "rule:admin_required",
    "identity:bar": "rule:admin_required"
}

To do this, you use the following configuration entry in the /etc/openstack_deploy/user_variables.yml file:

keystone_policy_overrides:
  identity:foo: "rule:admin_required"
  identity:bar: "rule:admin_required"

Note

The general format for the variable names used for overrides is <service>_policy_overrides. For example, the variable name used in this example to add a policy to the Identity service (keystone) policy.json file is keystone_policy_overrides.

Use this method for any files with the JSON format in OpenStack projects deployed in OpenStack-Ansible.

To assist you in finding the appropriate variable name to use for overrides, the general format for the variable name is <service>_policy_overrides.

Overriding .yml files

You can override .yml file values by supplying replacement YAML content.

Note

All default YAML file content is completely overwritten by the overrides, so the entire YAML source (both the existing content and your changes) must be provided.

For example, you might want to define a meter exclusion for all hardware items in the default content of the pipeline.yml file for the Telemetry service (ceilometer):

sources:
    - name: meter_source
    interval: 600
    meters:
        - "!hardware.*"
    sinks:
        - meter_sink
    - name: foo_source
    value: foo

To do this, you use the following configuration entry in the /etc/openstack_deploy/user_variables.yml file:

ceilometer_pipeline_yaml_overrides:
  sources:
      - name: meter_source
      interval: 600
      meters:
          - "!hardware.*"
      sinks:
          - meter_sink
      - name: source_foo
      value: foo

Note

The general format for the variable names used for overrides is <service>_<filename>_<file extension>_overrides. For example, the variable name used in this example to define a meter exclusion in the pipeline.yml file for the Telemetry service (ceilometer) is ceilometer_pipeline_yaml_overrides.

Overriding OpenStack upper constraints

Each OpenStack release uses an upper-constraints.txt file to define the maximum permitted version of each Python package. In some cases it may be necessary to override this file, for example when your local deployment needs to take advantage of a bug fix. Care should be taken when modifying this file as OpenStack services may not have been tested against more recent package versions.

To override the upper constraints for a deployment, clone the OpenStack requirements git repository, either storing it as a fork at a URL of your choice, or within the local filesystem of the host you are using to deploy OpenStack Ansible from. Once cloned, switch to the branch which matches the name of your deployed OpenStack version, and modify the upper constraints as required.

Next, edit your /etc/openstack_deploy/user_variables.yml file to indicate the path to the requirements git repository, and the git hash of the commit containing your changes using the requirements_git_repo and requirements_git_install_branch variables. When using the local filesystem, the requirements_git_repo should start with file://.

Finally, run the repo-install.yml playbook to upload these modified constraints to your repo host(s).