Building a highly available control plane
Back in the Folsom and Grizzly days, coming up with an High Availability (H/A) design for the OpenStack control plane was something of a black art. Many of the technologies recommended in the first iterations of the OpenStack High Availability Guide were specific to the Ubuntu distribution of Linux and were unavailable on the Red Hat Enterprise Linux-derived distributions.
The now-standard cluster resource manager (Pacemaker) was unsupported by Red Hat at that time. As such, architects using Ubuntu might use one set of software, those using CentOS or RHEL might use another set of software, and those using a Rackspace or Mirantis distribution might use yet another set of software. However, these days, the technology stack has converged and the H/A pattern is largely consistent regardless of the distribution used.
About failure and success
When we design a highly available OpenStack control plane, we're looking to mitigate two different scenarios...
