Cluster manager

A cluster manager is a resource that balances load and improves availability among SafeLinx Servers.

Each installation of a SafeLinx Server creates a single instance of a cluster manager resource. Using a cluster manager, you define a SafeLinx Server to be a principal node or subordinate node or both. A principal node dispatches traffic to other subordinate nodes. A subordinate node is configured to accept traffic from one or more principal nodes. A cluster manager that defines a SafeLinx Server as both a principal and subordinate node dispatches traffic and processes data.

Note: The local file system option does not support Clustering.

A SafeLinx Server that is configured exclusively as a subordinate node does not need MNC support installed, unless it is a messaging MNC. To dispatch traffic for a network, make sure that the SafeLinx Server that has the MNC support, which is installed and configured is the principal node in a cluster.

A principal node initiates communication to subordinate nodes. As part of the role of receiving and dispatching traffic, a principal node maintains two-way communication with subordinate nodes. Provide backup for SafeLinx Servers that are configured as principal nodes to make sure that critical resources are available.

Subordinate nodes send load information to principal nodes and control when to begin or end accepting traffic from principal nodes, which are based on a configurable distribution algorithm. The distribution algorithms include:
The principal node continuously repeats the sequence of distributing traffic to a series of subordinate nodes, one after the other.
Weighted round-robin
The principal node continuously repeats the sequence of distributing traffic to a series of subordinate nodes, which are based on configurable CPU utilization thresholds called low and high water marks.
Device/MNC based
The principal node distributes traffic to subordinate nodes, which are based on the MNC or unique device identifier from which it came.
Subordinate nodes can be configured to one of three states:
The normal mode of operation in which the cluster manager dispatches traffic according to the distribution algorithm configured for the subordinate node.
A mode of operation in which the cluster manager immediately notifies the subordinate node that it should abort any pending transactions.
A mode of operation in which the cluster manager does not route new traffic to this subordinate node, allowing the traffic to terminate after all pending transactions are completed. To verify that all traffic is terminated, use the wg_monitor utility on the SafeLinx Server system and check the number of active sessions.

When a principal node shuts down, the cluster manager notifies subordinate nodes that they should abort any pending transactions that get routed back through the principal node.

Subordinate nodes can be pooled into cluster groups and principal nodes can be limited to dispatching traffic only to subordinate nodes in these groups. By default, if a cluster manager has no groups to manage, it manages all subordinate nodes that are not assigned to a cluster group.