Ansible-deploy driver

Ansible is an already mature and popular automation tool, written in Python and requiring no agents running on the node being configured. All communications with the node are by default performed over secure SSH transport.

The Ansible-deploy deployment driver is using Ansible playbooks to define the deployment logic. It is not based on Ironic Python Agent (IPA) and does not generally need it to be running in the deploy ramdisk.

Note

The “playbook API”, that is the set and structure of variables passed into playbooks from the driver, is not stable yet and will most probably change in next versions.

Overview

The main advantage of this driver is extended flexibility in regards of changing and adapting node deployment logic to the particular use case, using the tooling already familiar to operators.

It also allows to shorten the usual feature development cycle of

  • implementing logic in ironic,
  • implementing logic in IPA,
  • rebuilding deploy ramdisk,
  • uploading it to Glance/HTTP storage,
  • reassigning deploy ramdisk to nodes,
  • restarting ironic service and
  • runing a test deployment

by using a more “stable” deploy ramdisk and not requiring ironic-conductor restarts (see Extending playbooks).

The main disadvantage is a synchronous manner of performing deployment/cleaning tasks, as Ansible is invoked as ansible-playbook CLI command via Python’s subprocess library.

Each action (deploy, clean) is described by single playbook with roles, which is run whole during deployment, or tag-wise during cleaning. Control of cleaning steps is through tags and auxiliary clean steps file. The playbooks for actions can be set per-node, as is cleaning steps file.

Features

Supports two modes for continuing deployment (configured in driver options, see Configuration file):

  • having the deploy ramdisk calling back to ironic API’s heartbeat endpoint (default)
  • polling the node until the ssh port is open as part of a playbook

User images

Supports whole-disk images and partition images:

  • compressed images are downloaded to RAM and converted to disk device;
  • raw images are streamed to disk directly.

For partition images the driver will create root partition, and, if requested, ephemeral and swap partitions as set in node’s instance_info by nova or operator. Partition table created will be of msdos type by default, the node’s``disk_label`` capability is honored if it is set in node’s instance_info.

Configdrive partition

Creating a configdrive partition is supported for both whole disk and partition images, on both msdos and GPT labeled disks.

Root device hints

Root device hints are currently supported in their basic form only (with exact matches, without oslo.utils operators). If no root device hint is provided for the node, first device returned as part of ansible_devices fact is used as root device to create partitions on or write the whole disk image to.

Node cleaning

Cleaning is supported, both automated and manual. Currently the driver has two default clean steps:

  • wiping device metadata
  • disk shredding

Their priority can be overridden via options in ironic configuration file’s [deploy] section the same as for IPA-based drivers.

As in the case of this driver all cleaning steps are known to conductor, booting the deploy ramdisk is completely skipped when there are no cleaning steps to perform.

Aborting cleaning tasks is not supported.

Logging

Logging is implemented as custom Ansible callback module, that makes use of oslo.log and oslo.config libraries and can re-use logging configuration defined in the main ironic configuration file (/etc/ironic/ironic.conf by default) to set logging for Ansible events, or use a separate file for this purpose.

Note

Currently this has some quirks in DevStack - due to default logging system there the log_file must be set explicitly in $playbooks_path/callback_plugins/ironic_log.ini when running DevStack in ‘developer’ mode using screen.

Requirements

ironic
Requires ironic version >= 8.0.0. (Pike release or newer).
Ansible
Tested with and targets Ansible ≥ 2.1

Bootstrap image requirements

  • password-less sudo permissions for the user used by Ansible
  • python 2.7.x
  • openssh-server
  • GNU coreutils
  • utils-linux
  • parted
  • gdisk
  • qemu-utils
  • python-requests (for ironic callback and streaming image download)
  • python-netifaces (for ironic callback)

Set of scripts to build a suitable deploy ramdisk based on TinyCore Linux, and an element for diskimage-builder is provided.

Setting up your environment

  1. Install ironic (either as part of OpenStack/DevStack or standalone)
  2. Install Ansible (pip install ansible should suffice).
  3. Install ironic-staging-drivers
  4. Edit ironic configuration file
    1. Add one of the Ansible-enabled drivers to enabled_drivers option. (see Available drivers and options).
    2. Add [ansible] config section and configure it if needed (see Configuration file).
  5. (Re)start ironic-conductor service
  6. Build suitable deploy kernel and ramdisk images
  7. Upload them to Glance or put in your HTTP storage
  8. Create new or update existing nodes to use the enabled driver of your choice and populate Driver properties for the Node when different from defaults.
  9. Deploy the node as usual.

Available drivers and options

Three drivers are provided:

pxe_ipmitool_ansible
Uses PXE/iPXE to boot of nodes, and ipmitool for Power/Management. This is the driver to use with real hardware nodes.
pxe_ssh_ansible
Uses PXE/iPXE to boot the nodes, and ironic’s SSH driver for Power/Management. Used only in testing environments.
pxe_libvirt_ansible
Alternative to pxe_ssh_ansible, uses LibVirt-based driver for Power/Management (part of ironic-staging-drivers). Can be used for bigger CI environments, where it is has better performance than ironic’s SSH driver.

Ansible-deploy options

Configuration file

Driver options are configured in [ansible] section of ironic configuration file.

use_ramdisk_callback
Whether to expect the callback from the deploy ramdisk when it is ready to accept command or use passive polling for running SSH daemon on the node as part of running playbooks. Note that setting it to False requires Neutron to resolve the IP of the node for Ansible to attempt connection to, and thus is not suitable for standalone deployment. Default is True.
verbosity
None, 0-4. Corresponds to number of ‘v’s passed to ansible-playbook. Default (None) will pass ‘vvvv’ when global debug is enabled in ironic, and nothing otherwise.
ansible_playbook_script
Full path to the ansible-playbook script. Useful mostly for testing environments when you e.g. run Ansible from source instead of installing it. Default (None) will search in $PATH of the user running ironic-conductor service.
playbooks_path
Path to folder that contains all the Ansible-related files (Ansible inventory, deployment/cleaning playbooks, roles etc). Default is to use the playbooks provided with ironic-staging-drivers from where it is installed.
config_file_path
Path to Ansible’s config file. When set to None will use global system default (usually /etc/ansible/ansible.cfg). Default is playbooks_path/ansible.cfg
ansible_extra_args
Extra arguments to pass to ansible-playbook on each invocation. Default is None.
extra_memory
Memory overhead (in MiB) for the Ansible-related processes in the deploy ramdisk. Affects decision if the downloaded user image will fit into RAM of the node. Default is 10.
post_deploy_get_power_state_retries
Number of times to retry getting power state to check if bare metal node has been powered off after a soft poweroff. Default is 6.
post_deploy_get_power_state_retry_interval
Amount of time (in seconds) to wait between polling power state after triggering soft poweroff. Default is 5.

Driver properties for the Node

Set them per-node via:

ironic node-update <node> <op> driver_info/<key>=<value>

or:

openstack baremetal node set <node> --driver-info <key>=<value>
ansible_deploy_username
User name to use for Ansible to access the node (default is ansible).
ansible_deploy_key_file
Private SSH key used to access the node. If none is provided (default), Ansible will use the default SSH keys configured for the user running ironic-conductor service. Also note, that for private keys with password, these must be pre-loaded into ssh-agent.
ansible_deploy_playbook
Name of the playbook file inside the playbooks_path folder to use when deploying this node. Default is deploy.yaml.
ansible_shutdown_playbook
Name of the playbook file inside the playbooks_path folder to use to gracefully shutdown the node in-band. Default is shutdown.yaml.
ansible_clean_playbook
Name of the playbook file inside the playbooks_path folder to use when cleaning the node. Default is clean.yaml.
ansible_clean_steps_config
Name of the YAML file inside the playbooks_path folder that holds description of cleaning steps used by this node, and defines playbook tags in ansible_clean_playbook file corresponding to each cleaning step. Default is clean_steps.yaml.

Customizing the deployment logic

Expected playbooks directory layout

The playbooks_path configured in the ironic config is expected to have a standard layout for an Ansible project with some additions:

<playbooks_path>
|
\_ inventory
\_ add-ironic-nodes.yaml
\_ roles
 \_ role1
 \_ role2
 \_ ...
|
\_callback_plugins
 \_ ...
|
\_ library
 \_ ...

The extra files relied by this driver are:

inventory
Ansible inventory file containing a single entry of conductor ansible_connection=local. This basically defines an alias to localhost. Its purpose is to make logging for tasks performed by Ansible locally and referencing the localhost in playbooks more intuitive. This also suppresses warnings produced by Ansible about hosts file being empty.
add-ironic-nodes.yaml
This file contains an Ansible play that populates in-memory Ansible inventory with access info received from the ansible-deploy driver, as well as some per-node variables. Include it in all your custom playbooks as the first play.

The default deploy.yaml playbook is using several smaller roles that correspond to particular stages of deployment process:

  • discover - e.g. set root device and image target
  • prepare - if needed, prepare system, for example create partitions
  • deploy - download/convert/write user image and configdrive
  • configure - post-deployment steps, e.g. installing the bootloader

Some more included roles are:

  • wait - used when the driver is configured to not use callback from node to start the deployment. This role waits for OpenSSH server to become available on the node to connect to.
  • shutdown - used to gracefully power the node off in-band
  • clean - defines cleaning procedure, with each clean step defined as separate playbook tag.

Extending playbooks

Most probably you’d start experimenting like this:

  1. Create a copy of deploy.yaml playbook, name it distinctively.
  2. Create Ansible roles with your customized logic in roles folder.
    1. In your custom deploy playbook, replace the prepare role with your own one that defines steps to be run before image download/writing. This is a good place to set facts overriding those provided/omitted by the driver, like ironic_partitions or ironic_root_device, and create custom partitions or (software) RAIDs.
    2. In your custom deploy playbook, replace the configure role with your own one that defines steps to be run after image is written to disk. This is a good place for example to configure the bootloader and add kernel options to avoid additional reboots.
  3. Assign the custom deploy playbook you’ve created to the node’s driver_info/ansible_deploy_playbook field.
  4. Run deployment.
    1. No ironic-conductor restart is necessary.
    2. A new deploy ramdisk must be built and assigned to nodes only when you want to use a command/script/package not present in the current deploy ramdisk and you can not or do not want to install those at runtime.

Variables you have access to

This driver will pass the single JSON-ified extra var argument to Ansible (as ansible-playbook -e ..). Those values are then accessible in your plays as well (some of them are optional and might not be defined):

ironic:
  nodes:
  - ip: <IPADDRESS>
    name: <NODE_UUID>
    user: <USER ANSIBLE WILL USE>
    extra: <COPY OF NODE's EXTRA FIELD>
  image:
    url: <URL TO FETCH THE USER IMAGE FROM>
    disk_format: <qcow2|raw|...>
    container_format: <bare|...>
    checksum: <hash-algo:hashstring>
    mem_req: <REQUIRED FREE MEMORY TO DOWNLOAD IMAGE TO RAM>
    tags: <LIST OF IMAGE TAGS AS DEFINED IN GLANCE>
    properties: <DICT OF IMAGE PROPERTIES AS DEFINED IN GLANCE>
  configdrive:
    type: <url|file>
    location: <URL OR PATH ON CONDUCTOR>
  partition_info:
    label: <msdos|gpt>
    preserve_ephemeral: <bool>
    ephemeral_format: <FILESYSTEM TO CREATE ON EPHEMERAL PARTITION>
    partitions: <LIST OF PARTITIONS IN FORMAT EXPECTED BY PARTED MODULE>

Some more explanations:

ironic.nodes
List of dictionaries (currently of only one element) that will be used by add-ironic-nodes.yaml play to populate in-memory inventory. It also contains a copy of node’s extra field so you can access it in the playbooks. The Ansible’s host is set to node’s UUID.
ironic.image

All fields of node’s instance_info that start with image_ are passed inside this variable. Some extra notes and fields:

  • mem_req is calculated from image size (if available) and config option [ansible]extra_memory.
  • if checksum initially does not start with hash-algo:, hashing algorithm is assumed to be md5 (default in Glance).
ironic.partiton_info.partitions

Optional. List of dictionaries defining partitions to create on the node in the form:

partitions:
- name: <NAME OF PARTITION>
  unit: <UNITS FOR SIZE>
  size: <SIZE OF THE PARTITION>
  type: <primary|extended|logical>
  align: <ONE OF PARTED_SUPPORTED OPTIONS>
  format: <PARTITION TYPE TO SET>
  flags:
    flag_name: <bool>

The driver will populate this list from root_gb, swap_mb and ephemeral_gb fields of instance_info. The driver will also prepend the bios_grub-labeled partition when deploying on GPT-labeled disk, and pre-create a 64MiB partiton for configdrive if it is set in instance_info.

Please read the documentation included in the ironic_parted module’s source for more info on the module and its arguments.

ironic.partiton_info.ephemeral_format
Optional. Taken from instance_info, it defines file system to be created on the ephemeral partition. Defaults to the value of [pxe]default_ephemeral_format option in ironic configuration file.
ironic.partiton_info.preserve_ephemeral
Optional. Taken from the instance_info, it specifies if the ephemeral partition must be preserved or rebuilt. Defaults to no.

As usual for Ansible playbooks, you also have access to standard Ansible facts discovered by setup module.

Included custom Ansible modules

The provided playbooks_path/library folder includes several custom Ansible modules used by default implementation of deploy and prepare roles. You can use these modules in your playbooks as well.

stream_url
Streaming download from HTTP(S) source to the disk device directly, tries to be compatible with Ansible’s get_url module in terms of module arguments. Due to the low level of such operation it is not idempotent.
ironic_parted
creates partition tables and partitions with parted utility. Due to the low level of such operation it is not idempotent. Please read the documentation included in the module’s source for more information about this module and its arguments. The name is chosen so that the parted module included in Ansible 2.3 is not shadowed.