Chapter 1. Heartbeat as a Cluster Messaging Layer

Heartbeat is a daemon that provides cluster infrastructure (communication and membership) services to its clients. This allows clients to know about the presence (or disappearance!) of peer processes on other machines and to easily exchange messages with them.

In order to be useful to users, the Heartbeat daemon needs to be combined with a cluster resource manager (CRM) which has the task of starting and stopping the services (IP addresses, web servers, etc) that cluster will make highly available. The canonical cluster resource manager typically associated with Heartbeat is Pacemaker, a highly scalable and feature-rich implementation that supports both Heartbeat and, alternatively, the Corosync cluster messaging layer.


Up until Heartbeat release 2.1.3, Pacemaker was developed jointly with Heartbeat as part of the Linux-HA umbrella project. After this release, the Pacemaker project was spun off as a separate project and continues as such, while maintaining full support for Heartbeat cluster messaging.