Consensus Cluster Membership (CCM) Module

The Consensus Cluster Membership module was originally created by RamPai[1], and is designed to provide subscribers with information about sets of FullyConnected[2] nodes in the current cluster partition.

This information includes new additions to the membership, lost nodes, loss of quorum. It can deliver this information using either the SAF[3] API or a an early draft of the OCF[4] membership API (the latter API is more commonly used in the project, but the other should also work).

It is the middle "membership" layer that sits between Heartbeat (a messaging/infrastructure layer) and the new ClusterResourceManager[5] (a resource allocation layer).

Using an enahanced version of an early draft of the OCF membership API, it now provides all of the following node information during events published to subscribers:

• Node Id      (int)   : An int index for the node

• Node UUID    (char*) : A 128-bit guaranteed unique identifier for the node.

• Node Born on (int)   : The cluster's generation counter at the time this node joined.

• Node uname   (char*) : The Nodes hostname as determined by uname -n

The last two are used as part of the DesignatedCoordinator[6]'s election process.

The order of the list of nodes given is consistent for every member in the partition.

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This information provided courtesy of the Linux-HA project at http://linux-ha.org/