Programming Guides › Programming Guide for Perl › Policy Management Operations › Manage Policy Server Load Distribution › Cluster Configuration

Cluster Configuration

A cluster is stored in a host configuration object. Cluster failover occurs according to the following configuration values set in PolicyMgtHostConfig:

• Failover threshold. The minimum percentage of servers within a cluster that must be available for Policy Server requests. If the number of available servers falls below the threshold, failover to the next cluster occurs.

  The failover threshold percentage applies to all clusters associated with the host configuration object.

  To determine the number of servers that the percentage represents in any given cluster, multiply the threshold percentage by the number of servers in the cluster, rounding up to the next highest integer. For example:

  • With a 60-percent failover threshold for a cluster of five servers, failover to the next cluster occurs when the number of available servers in the cluster falls below 3.
  • With a 61-percent failover threshold for the same cluster, failover occurs when the number of available servers falls below 4.

  Set through: FailoverThreshold().

• Server timeout. The maximum time an agent will wait for a response from a server. If the wait time exceeds the server timeout value, the server is considered inactive, and failover to the next server occurs.

  If a server timeout occurs within a cluster, and the timeout causes the cluster's failover threshold to be exceeded, failover to the next cluster occurs.

  Set through: RequestTimeout().

• Sequence of cluster failover. When cluster failover occurs, SiteMinder sends subsequent Policy Server requests to the next cluster in the cluster sequence. Cluster sequence is determined by the order of cluster objects in the cluster array.

  Add clusters through: AddCluster(). The newly added cluster is added to the end of the cluster array.

  Retrieve the cluster array through: GetAllClusters().

  The order in which you add clusters to a host configuration object determines the failover sequence. The first cluster you add (that is, the first cluster in the cluster array) is the primary cluster. This is the cluster that is used as long as the number of available servers in the cluster does not fall below the failover threshold. If there are not enough available servers in the primary cluster, failover to the next cluster occurs—that is, to the second cluster that was added to the host configuration object. If that cluster also fails, failover to the third cluster added to the host configuration object occurs, and so on.