Comment 16 for bug 1251345

Tried a brand new cluster controller using maas version 1.2+bzr1373+dfsg-0ubuntu1~12.04.5 from precise.
Same problem with all cluster controllers,
so problem seems to be on the region controller side.

Traced the origin of the issue to an apt-get dist-upgrade which upgraded the packages as follows:
Start-Date: 2014-03-29 00:43:39
Commandline: apt-get dist-upgrade
Install: python-jsonschema:amd64 (1.3.0-0ubuntu1~cloud0, automatic), librbd1:amd64 (0.67.4-0ubuntu2.2~cloud0, automatic), libnss3:amd64 (3.15.4-0ubuntu0.12.04.1, automatic), python-d2to1:amd64 (0.2.10-1ubuntu4~cloud0, automatic), libaugeas0:amd64 (0.10.0-0ubuntu4, automatic), python-mock:amd64 (1.0.1-2~cloud0, automatic), augeas-lenses:amd64 (0.10.0-0ubuntu4, automatic), python-oslo.config:amd64 (1.2.1-0ubuntu1~cloud0, automatic), librados2:amd64 (0.67.4-0ubuntu2.2~cloud0, automatic), libnetcf1:amd64 (0.1.9-2ubuntu3.2, automatic), python-bson-ext:amd64 (2.6-1~cloud1, automatic), python-swiftclient:amd64 (1.6.0-0ubuntu1~cloud0, automatic), python-amqp:amd64 (1.0.12-0ubuntu1~cloud0, automatic), libnl-route-3-200:amd64 (3.2.3-2ubuntu2, automatic), python-cinderclient:amd64 (1.0.6-0ubuntu1~cloud0, automatic), python-passlib:amd64 (1.5.3-0ubuntu1, automatic), libboost-thread1.46.1:amd64 (1.46.1-7ubuntu3, automatic), libnspr4:amd64 (4.9.5-0ubuntu0.12.04.2, automatic), python-urllib3:amd64 (1.6-2~ubuntu12.04.1~ppa1, automatic), python-keystoneclient:amd64 (0.3.2-0ubuntu1~cloud0, automatic), libxen-4.3:amd64 (4.3.0-1ubuntu1.1~cloud0, automatic), libaudit0:amd64 (1.7.18-1ubuntu1, automatic), python-requests:amd64 (1.2.3-1~ubuntu12.04.1~ppa1, automatic)
Upgrade: maas-dns:amd64 (1.4+bzr1693+dfsg-0ubuntu2.2~ctools0, 1.4+bzr1693+dfsg-0ubuntu2.3~ctools0), maas-common:amd64 (1.4+bzr1693+dfsg-0ubuntu2.2~ctools0, 1.4+bzr1693+dfsg-0ubuntu2.3~ctools0), openssh-server:amd64 (5.9p1-5ubuntu1.1, 5.9p1-5ubuntu1.2), glance-common:amd64 (2012.1.3+stable-20130423-74b067df-0ubuntu1, 2013.2.2-0ubuntu1~cloud0), python-maas-client:amd64 (1.4+bzr1693+dfsg-0ubuntu2.2~ctools0, 1.4+bzr1693+dfsg-0ubuntu2.3~ctools0), libxenstore3.0:amd64 (4.1.5-0ubuntu0.12.04.3, 4.3.0-1ubuntu1.1~cloud0), python-paramiko:amd64 (1.7.7.1-2ubuntu1, 1.10.1-1~cloud0), python-migrate:amd64 (0.7.2-1ubuntu1, 0.7.2-6~cloud0), libvirt0:amd64 (0.9.8-2ubuntu17.17, 1.1.1-0ubuntu8.5~cloud0), openssh-client:amd64 (5.9p1-5ubuntu1.1, 5.9p1-5ubuntu1.2), python-anyjson:amd64 (0.3.1-1build1, 0.3.3-1~cloud0), python-django-maas:amd64 (1.4+bzr1693+dfsg-0ubuntu2.2~ctools0, 1.4+bzr1693+dfsg-0ubuntu2.3~ctools0), python-greenlet:amd64 (0.3.1-1ubuntu5.1, 0.4.1-0ubuntu2~cloud1), python-glance:amd64 (2012.1.3+stable-20130423-74b067df-0ubuntu1, 2013.2.2-0ubuntu1~cloud0), python-sqlalchemy:amd64 (0.7.4-1ubuntu0.1, 0.8.2-1~cloud1), python-boto:amd64 (2.2.2-0ubuntu3, 2.9.6-1~cloud0), python-simplejson:amd64 (2.3.2-1, 3.3.0-2ubuntu2~cloud1), python-bson:amd64 (2.1-1ubuntu0.1, 2.6-1~cloud1), python-webob:amd64 (1.1.1-1ubuntu0, 1.2.3-2ubuntu1~cloud0), maas-region-controller:amd64 (1.4+bzr1693+dfsg-0ubuntu2.2~ctools0, 1.4+bzr1693+dfsg-0ubuntu2.3~ctools0), python-prettytable:amd64 (0.5-1ubuntu2, 0.6.1-1ubuntu1~cloud0), python-novaclient:amd64 (2012.1-0ubuntu1, 2.15.0-0ubuntu1~cloud0), maas-cluster-controller:amd64 (1.4+bzr1693+dfsg-0ubuntu2.2~ctools0, 1.4+bzr1693+dfsg-0ubuntu2.3~ctools0), python-kombu:amd64 (1.4.3-1, 2.5.12-0ubuntu2~cloud1), python-netaddr:amd64 (0.7.5-4build2, 0.7.7-1~cloud0), python-maas-provisioningserver:amd64 (1.4+bzr1693+dfsg-0ubuntu2.2~ctools0, 1.4+bzr1693+dfsg-0ubuntu2.3~ctools0), python-sqlalchemy-ext:amd64 (0.7.4-1ubuntu0.1, 0.8.2-1~cloud1), libvirt-bin:amd64 (0.9.8-2ubuntu17.17, 1.1.1-0ubuntu8.5~cloud0), python-eventlet:amd64 (0.9.16-1ubuntu4.2, 0.13.0-0ubuntu1~cloud0), libusb-1.0-0:amd64 (1.0.9~rc3-2ubuntu1, 1.0.16-3~cloud2), maas:amd64 (1.4+bzr1693+dfsg-0ubuntu2.2~ctools0, 1.4+bzr1693+dfsg-0ubuntu2.3~ctools0), python-crypto:amd64 (2.4.1-1ubuntu0.1, 2.6-5~cloud1), maas-dhcp:amd64 (1.4+bzr1693+dfsg-0ubuntu2.2~ctools0, 1.4+bzr1693+dfsg-0ubuntu2.3~ctools0), maas-cli:amd64 (1.4+bzr1693+dfsg-0ubuntu2.2~ctools0, 1.4+bzr1693+dfsg-0ubuntu2.3~ctools0)
Remove: glance-client:amd64 (2012.1.3+stable-20130423-74b067df-0ubuntu1)
End-Date: 2014-03-29 00:47:56

So, the upgrade to maas 1.4+bzr1693+dfsg-0ubuntu2.3~ctools0 from 1.4+bzr1693+dfsg-0ubuntu2.2~ctools0 on the region controller now means that no cluster controllers can connect to the region controller.