live-migration: default auth-type to ssh, enforce better value checking

[Fabricio Costi]

nova.cfg >>
nova-compute:
    openstack-origin: cloud:trusty-juno
    enable-resize: true
    enable-live-migration: true
    migration-auth-type: "none"
    sysctl: '{ kernel.pid_max : 4194303 }'
    libvirt-image-backend: rbd

libvirtd.conf >>
#listen_tcp = 1
#auth_tcp = "sasl"

After running live-migration command, the log from the original host of a given vm:

/var/log/nova/nova-compute.log >>
2015-03-13 00:30:01.062 1796 ERROR nova.virt.libvirt.driver [-] [instance: 92e1fb07-1bbe-4209-a98d-bae5e1d6a36c] Live Migration failure: operation failed: Failed to connect to remote libvirt URI qemu+tcp://maas-pute-04/system: unable to connect to server at 'maas-pute-04:16509': Connection refused

After changing the config on the /var/lib/juju/agents/unit-nova-compute-1/charm/templates/libvirtd.conf to reflect the intended config (tcp_listen = 1 and auth_tcp = "none") and restarting the service, it throws a config-changed hook error. After running the config-changed hook, it works and I am able to live-migrate between the nodes with the correct config.

[James Page (james-page)]

AFAIR the only auth-type supported by the charm is SSH - not using any type of auth was considered insecure so was not supported.

That said it feels like the charm could do better with enforcing that and providing feedback to charm users; even changing the default to 'ssh' would be better than the current situation we have where its possible to enable live-migration and end up with a non-functional deployment.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/506655
Committed: https://git.openstack.org/cgit/openstack/charm-nova-compute/commit/?id=1ce182bce77732cf7d9f7cd9c9ba1eaca0c969ab
Submitter: Jenkins
Branch: master

commit 1ce182bce77732cf7d9f7cd9c9ba1eaca0c969ab
Author: Liam Young <email address hidden>
Date: Fri Sep 22 13:25:42 2017 +0000

    Mark charm blocked for invalid migrations settings

    Previously if enable-live-migration was true and migration-auth-type
    was anything other than "ssh" then migration setup would be invalid.
    The change puts the charm in a blocked state to make it clear that
    the migration settings are not valid.

    Change-Id: I796b54e9a08e8eab5c2b316a2aff0b29ee7e6bd9
    Closes-Bug: #1431685