Multiple drivers support for nova_compute container

[Lingfeng Xiong]

nova_compute container installs nova-compute package for now. This package automatically installs nova-compute-kvm. There are some problem with this approach:
1. By installing nova-compute-kvm, it introduces a hard dependency of kvm and eliminate the possibilities configuring nova_compute container to use other drivers, for example, xen through libvirt.
2. nova-compute-kvm contains a configuration file (/etc/nova/nova-compute.conf). This file cannot be overriden with current ansible script.

Because nova-compute cannot be installed independently, I think we have three ways to workaround:
1. Add a parameter in globals.yml, e.g. nova_driver. Build images based on the value of this parameter.
2. Do not install nova-compute at building time. Instead, dynamically install corresponding nova-compute-* packages based on the parameter set in globals.yml through extend_start.sh.
3. Install any of those packages, then offer a way to override nova-compute.conf (just like nova.conf).

Which way is better?

[Sam Yaple (s8m)]

xen, libvirt, qemu

All of those can be made configurable

[zhubingbing (zhubingbing)]

you can setting nova-compute.conf virt_type=kvm ort öemu or xen
[libvirt]
virt_type=qemu
http://docs.openstack.org/developer/kolla/quickstart.html