Cluster Glue is a set of libraries, tools and utilities suitable for the Heartbeat/Pacemaker cluster stack. In essence, Glue is everything that is not the cluster messaging layer (Heartbeat), nor the cluster resource manager (Pacemaker), nor a Resource Agent.
Cluster Glue has been managed as a separate Linux-HA sub-project since its 1.0 release, which coincided with the Heartbeat 2.99 release. Previously, it was a part of the then-monolithic Heartbeat project, and had no separate name.
Local Resource Manager (LRM)
The Local Resource Manager is the interface between the Cluster Resource Manager (Pacemaker) and the resource agents. It is itself not cluster aware, nor does it apply any policies. It simply processes commands received from the Cluster Resource Manager, passes them to resource agents, and reports back success or failure. It particular, the LRM may
- start a resource;
- stop a resource;
- monitor a resource;
- report a resource's status;
- list all resource instances it currently controls, and their status.
A mechanism for node fencing. In case a node is considered "dead" by the cluster as a whole, STONITH ("Shoot The Other Node In The Head") forcefully removes is from the cluster so it can no longer pose a risk of interacting with other nodes in an uncoordinated fashion.
An advanced error reporting utility. hb_report-generated tarballs are frequently requested by the developers to isolate and fix bugs, and are commonly found as attachments to Bugzilla entries. See Reporting Utility for more details.
Cluster Plumbing Library
A low-level library for intra-cluster communications.
Source Code Repository
Source code for Cluster Glue is being maintained in the http://hg.linux-ha.org/glue Mercurial Repository.