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Session lingering is an complementary option to session prelanuch and in most XenApp implementations both these option will be used together to provide the best user experience and to make access to published resources fast and easy. Session lingering similar to session prelaunch was reintroduced in XenApp and XenDesktop 7.6

Introduction 

It may happen, that users by mistake close a published application and when they restart the same application, there might be a delay in the display of the application because the session creation and connection takes time. Session lingering prevents a session from being closed as soon as the user ends the last published application in a session. Instead of logging off, the session is silently retained to provide very short reaction time for future access to published applications.
The readiness time can be of course configured, configuration process will be described in the How to configure section below.

Key considerations:

The following conditions must be considered when session lingering is going to be used:

  • Session lingering is configured per Delivery Group
  • The Delivery Group must support applications. If you configure delivery group to deliver only desktops, prelaunch and linger screens will not be available in Edit Delivery Group wizard.
  • Session lingering is available only for the machines must be running a VDA for Server OS, minimum version 7.6.

Note: Please see section Licensing and resource implications in my previous post: XenApp and XenDesktop 7.6 session prelaunch explained.

How to configure ?

To be able to utilize session lingering the following configuration task must be completed:

  1. Configure StoreFront 2.6 for Pass Through Authentication – to configure StoreFront for pass-through authentication follow the steps below:
    1. Open Citrix StoreFront console
    2. In the left pane select Authentication
    3. In the right pane  (Action pane) click Add/Remove Method
    4. Select Domain pass-through and Accept settings
    5. Verify domain pass-through is added and enabled if as it is shown in Figure 1
prel_1

Figure 1

 

  • Enable and configure Session Lingering on XenDesktop 7.6 delivery group – to enable session lingering follow the steps below:
    1. Open Citrix Studio
    2. In the left pane select Delivery Groups
    3. In the middle pane select the delivery group you want to modify
    4. In the right  pane  (Action pane) click Edit Delivery Group
    5. On the left side select Application Lingering and configure required settings.
    6. You can configure 2 behaviors:
      1. If lingering session will be created – by default lingering is disabled.
      2. How long lingering session remain active – there are two methods to specify how long an unused session remains active when the user does not start an application: a configured timeout and server load thresholds. You can configure all of them; the event that occurs first will cause the unused session to end.
  • Timeout – you can configure the time interval 1-99 days, 1-2376 hours, or 1-142,560 minutes.

    Thresholds – you can configure two thresholds: the average load on all machines in the Delivery Group exceeds a specified percentage (1-99%) and the load on any machine in the Delivery Group exceeds a specified percentage (1-99%). When a threshold is exceeded, the sessions that have been in lingering state for the longest time are ended, sessions are ended one-by-one at minute intervals until the load falls below the threshold. (While the threshold is exceeded, no new lingering sessions are started.)

    Note: In Citrix Studio you can setup only termination timeout. Time before disconnection (disconnection timeout) can be changed using powershell cmdlet.

    The example is shown in Figure 2 below sling_2

    How to verify if session lingering is working  ?

    In order to verify if session lingering is configured you can do either:

    • select the delivery group in Citrix Studio. The result is shown in the Figure 4.sling_5

     

    • run powershell cmdlet Get-BrokerSessionLinger. The result is shown in the Figure 5  sling_3

     

    • run powershell cmdlet Get-BrokerSession. The result is shown in the Figure 5  sling_4