charms-openstack module: https://github.com/openstack-charmers/charms.openstack/pull/8
charm openstack layer: https://github.com/openstack-charmers/charm-layer-openstack/pull/6
openstack-ha interface: https://github.com/gnuoy/interface-openstack-ha
hacluster interface: https://github.com/openstack-charmers/charm-interface-hacluster/pull/2