Product Documentation

Overriding Persistence Settings for Overloaded Services

Aug 31, 2016

When a service is loaded or is otherwise unavailable, service to clients is degraded. To work around this situation, you might have to configure the NetScaler appliance to temporarily forward to other services the requests that would otherwise be included in the persistence session that is associated with the overloaded service. In other words, you might have to override the persistence setting that is configured for the load balancing virtual server. You can achieve this functionality by setting the skippersistency parameter. With the parameter set, when the virtual server receives new connections for an overloaded service, the virtual server disregards any existing persistence sessions that are associated with that service, until the service returns to a state at which it can accept requests. Persistence sessions associated with other services are not affected. The functionality is available for only virtual servers whose type is ANY or UDP.

In Branch Repeater load balancing configurations, you must also configure a load monitor and bind it to the service. The monitor takes the service out of subsequent load balancing decisions until the load on the service is brought below the configured threshold. For information about configuring a load monitor for your virtual server, see Understanding Load Monitors.

You can configure the virtual server to perform one of the following actions with the requests that would otherwise form a part of the persistence session:
  • Send each request to one of the other services. The virtual server takes a load balancing decision and sends each request to one of the other services on the basis of the configured load balancing method. If all the services are overloaded, requests are dropped until a service becomes available.

    Both wildcard and IP address–based virtual servers support this option. This action is appropriate for all deployments, including deployments in which the virtual server is load balancing Branch Repeater appliances or firewalls.

  • Bypass the virtual server-service configuration. The virtual server does not take a load balancing decision. Instead, it simply bridges each request through to a physical server on the basis of the destination IP address in the request.

    Only wildcard virtual servers of type ANY and UDP support the bypass option. Wildcard virtual servers have a *:* IP and port combination. This action is appropriate for deployments in which you are using the virtual server to load balance Branch Repeater appliances or firewalls. In these deployments, the NetScaler appliance first forwards a request to a Branch Repeater appliance or firewall, and then forwards the processed response to a physical server. If you configure the virtual server to bypass the virtual server–service configuration for overloaded services, if a Branch Repeater appliance or firewall gets overloaded, the virtual server bridges requests directly to their destination IP addresses until the Branch Repeater appliance or firewall can accept requests.

To override persistence settings for overloaded services by using the command line interface

At the command prompt, type the following commands to override persistence settings for overloaded services and verify the configuration:

  • set lb vserver <name> -skippersistency <skippersistency>
  • show lb vserver <name>

Example

> set lb vserver mylbvserver -skippersistency ReLb 
 Done 
> show lb vserver mylbvserver 
	mylbvserver (*:*) - ANY	Type: ADDRESS  
	  . . . 
	  . . .	 
 Skip Persistency: ReLb 
	  . . . 
 Done 
>

To override persistence settings for overloaded services by using the configuration utility

  1. Navigate to Traffic Management > Load Balancing > Virtual Servers and select the virtual server of type UDP or ANY.
  2. In the Advanced Settings pane, select Traffic Settings, and specify the type of Skip Persistency.