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    High Availability Overview

    High Availability (HA) on NorthStar Controller is an active/standby solution. That means that there is only one active node at a time, with all other nodes in the cluster serving as standby nodes. All of the nodes in a cluster must be on the same local subnet for HA to function. On the active node, all processes are running. On the standby nodes, those processes required to maintain connectivity are running, but NorthStar processes are in a stopped state. If the active node experiences a connectivity failure, the standby nodes elect a replacement active node from amongst themselves, and complete failover is achieved within five minutes. One of the factors in the selection of the new active node is the user-configured priorities of the candidate nodes.

    All processes are started on the new active node, and the node acquires the virtual IP address that is required for the client-facing interface. This address is always associated with the active node, even if failover causes the active node to change.

    Failure Scenarios

    NorthStar Controller HA protects the network from the following failure scenarios:

    • Hardware failures (server power outage, server interfaces or Ethernet cable failure)
    • Operating system failures (server operating system reboot, server operating system not responding)
    • Software failures (failure of any process running on the active server when it is unable to recover locally)

    Failover and the NorthStar Controller User Interfaces

    If failover occurs while you are working in the NorthStar Controller Java client, the client is disconnected and you will see an error message similar to the one shown in Figure 1.

    Figure 1: Java Client Failover Indication

    Java Client Failover

    You must re-launch NorthStar Controller using the client-facing interface virtual IP address.

    The Web UI also loses connectivity upon failover, requiring you to log in again. Once you log in, you can check the HA dashboard widget to see which server in the cluster has taken over the role of active server. Click Dashboard in the top menu bar to display the Dashboard view.

    The Dashboard widget displays the name of each node in the cluster, along with its role as Active or Standby, and its status as Up or Down. Figure 2 shows an example.

    Figure 2: Cluster Status Widget

    Cluster Status Widget

    Cluster Configuration

    The NorthStar implementation of HA requires that the cluster have an odd number of nodes and a minimum of three. There is an option within the NorthStar Controller setup utility for configuring an HA cluster. First, configure the standalone servers; then configure the cluster. See Configuring a Cluster for High Availability for step-by-step cluster configuration instructions.

    Ports that Must be Allowed by External Firewalls

    Among the ports used by NorthStar, there are a number that must be allowed by external firewalls in order for NorthStar Controller servers to communicate. See Understanding the NorthStar Controller for a list of ports used by NorthStar Controller that must be allowed by external firewalls. The ports with the word cluster in their purpose descriptions pertain specifically to HA configuration.

    Modified: 2016-05-10