Support Xen Virt Driver

date:2016-06-03 11:17
tags:ansible, xen

The purpose of this spec is to add support for the Xen Hypervisor to OpenStack-Ansible. This will allow the use of Xen as an option on OpenStack compute nodes.

https://blueprints.launchpad.net/openstack-ansible/+spec/xen-virt-driver

Problem description

Xen is a tested and supported hypervisor in OpenStack. It is used in some of the largest public clouds today and would make a good addition to OpenStack-Ansible. Support for Xen exists in the OpenStack Libvirt Driver today so implementation should not be difficult.

Proposed change

The primary change is to add support in OpenStack-Ansible for Xen on CentOS 7, Ubuntu 16.04, and Ubuntu 14.04 (by using UCA repos). The necessary changes for Xen to work with OpenStack are in Xen 4.5.1 and Libvirt 1.2.15. This blueprint covers deploying the nova-xen compute driver with the standard networking agents that OpenStack-Ansible supports.

The proposed changes include:

  • Add support for installing/configuring the Xen virt driver and dependencies
  • Documentation for how to configure a compute to run the Xen virt driver
  • Tests to verify changes to the os_nova role required for Xen support

Alternatives

  • Maintain independent Xen Ansible playbooks - This requires reinvention of base function and does not meet operator requirements.

Playbook/Role impact

See the Work Items for the playback/role impact. References to nova_virt_type will be updated to reflect a ‘xen’ option.

Upgrade impact

None. The xen driver is new for OpenStack-Ansible, and as such has no upgrade impact.

Security impact

None.

Performance impact

None.

End user impact

End users will be able to deploy compute nodes using the Xen virt driver.

Deployer impact

Xen specific configuration options will be added to the openstack-ansible-os_nova role.

When support for Xen as a virt driver is added these config options will be available for use; however it is expected that Xen support will be disabled by default, requiring that deployers explicitly enable Xen support and configure hosts for OpenStack-Ansible to use.

Documentation of these new configuration items will be provided and a set of defaults will also be provided. The Xen virt driver has limited its configuration to be minimal, so the operators should only have a few required options to set when Xen is selected as the virt driver.

Developer impact

The existing development team will be asked for reviews and approvals of the change sets. The Xen driver team will do the necessary implementation and support of this function.

Dependencies

Implementation

Assignee(s)

Primary assignee:
Antony Messerli - antonym on IRC and Launchpad

Other contributors:

Work items

Multiple changes would be needed:

  • Add ‘xen’ to the ‘nova_virt_types’ structure alongside the necessary variable requirements for driver configuration, matching the other compute types.
  • As required, add nova.conf templating for xen-specific configuration options that is conditionally included when nova_virt_type is ‘xen’.
  • Create a new nova_compute_xen.yml in the openstack-ansible-os_nova project. This will contain the tasks needed to ensure the xen driver is installed and configured on the system.
  • Update the existing nova_compute.yml to include the nova_compute_xen.yml and add the appropriate conditionals for that import.
  • Create a new nova_compute_xen_install.yml, which will be included by nova_compute_xen.yml. It will ensure that the necessary configuration and dependencies for running the Xen driver are in place.
  • Update documentation and comments indicating the new Xen nova_virt_type and how to configure OpenStack-Ansible for the Xen driver.
  • Automated unit test (see Testing)

Testing

A new test-install-nova-xen.yml will be created for validating the new xen playbooks within the openstack-ansible-os_nova project.

Documentation impact

Documentation covering how to enable and configure Xen support will be added to the user guide.