29장. Multi-site Pacemaker clusters

The Booth ticket manager is a distributed service that is meant to be run on a different physical network than the networks that connect the cluster nodes at particular sites. It yields another, loose cluster, a Booth formation, that sits on top of the regular clusters at the sites. This aggregated communication layer facilitates consensus-based decision processes for individual Booth tickets.

A Booth ticket is a singleton in the Booth formation and represents a time-sensitive, movable unit of authorization. Resources can be configured to require a certain ticket to run. This can ensure that resources are run at only one site at a time, for which a ticket or tickets have been granted.

You can think of a Booth formation as an overlay cluster consisting of clusters running at different sites, where all the original clusters are independent of each other. It is the Booth service which communicates to the clusters whether they have been granted a ticket, and it is Pacemaker that determines whether to run resources in a cluster based on a Pacemaker ticket constraint. This means that when using the ticket manager, each of the clusters can run its own resources as well as shared resources. For example there can be resources A, B and C running only in one cluster, resources D, E, and F running only in the other cluster, and resources G and H running in either of the two clusters as determined by a ticket. It is also possible to have an additional resource J that could run in either of the two clusters as determined by a separate ticket.