Using Worker Groups for Enhanced Resource Access

Worker groups are collections of XenApp servers, residing in the same farm, that are managed as a single unit. Using worker groups, you can:
  • Streamline application publishing to multiple farm servers
  • Load balance access to published resources
  • Filter policies so that settings are applied only to sessions hosted on a specific set of farm servers
When using worker groups, consider the following:
  • A farm server can belong to multiple worker groups
  • A worker group can include any number of XenApp servers or none at all
  • Only servers that belong to the same XenApp farm are included in a worker group

Publishing Applications

When publishing an application, you can use worker groups to specify the servers hosting the application. To increase capacity for the application, you can add more servers to the worker group rather than modify the application properties. If your environment includes Active Directory, you can create the worker group based on the Organizational Unit (OU) that includes the servers hosting the application. To increase capacity for the application, you add servers to the OU. New servers that you add to the OU are automatically included in the worker group.

When adding servers to worker groups for application publishing, all XenApp servers in the worker group must have the application installed. When a user attempts to launch an application, XenApp checks to ensure the application is installed on the farm servers in the worker group. If the application is not installed, the application does not launch and an error is logged to the Application event log on the data collector.

Load Balancing Access to Published Resources

To ensure an optimal experience for users accessing published resources, XenApp provides load balancing policies to direct users to the least-loaded XenApp server hosting the resource. You can use load balancing policies to:
  • Reduce WAN traffic by directing users to the closest regional server
  • Direct users to a backup server in the event of an outage
  • Direct a specific group of users to a group of dedicated servers
Load balancing policies consist of the following elements:
  • A filter to determine when the policy is applied
  • A worker group preference list to determine the servers to which users are directed when logging on

When you create a load balancing policy, configure a filter so that the load balancing policy can be applied to users when they access published resources. If you do not configure a filter, the load balancing policy will have no effect when users log on. As with other Citrix policies, you can filter based on access control, client IP address, client name, and users.

Additionally, to ensure users are directed to the appropriate servers, create a worker group preference list to prioritize the servers that users can access. A priority of 1 is considered the highest priority. When a user launches a published application, the load balancing policy directs the user to servers in the highest priority worker groups first. Users are directed to servers in lower priority worker groups if servers in the higher priority worker groups are offline or have reached maximum capacity. Users are not directed to servers in worker groups that are not included in the worker group preference list. If a user attempts to launch an application that is not installed on any servers in any of the listed worker groups, regardless of priority, the launch attempt fails and an error is logged to the Application event log on the data collector.

After you create load balancing policies, you prioritize them just as you would any other Citrix policy. If multiple load balancing policies apply to a single user, XenApp uses the worker group preference list from the highest priority policy to direct the user. Preference lists from lower priority load balancing policies are not considered.

Using Worker Groups to Filter Policies

You can use worker groups as filters in Citrix policies to apply policy settings to connections. When adding the filter, you specify the worker group by name only. If the worker group is subsequently renamed or deleted, XenApp no longer recognizes the filter and the policy is not applied to any connections.

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