Configure session prelaunch and session linger – Citrix Website/Blogs/Citrix TV

Citrix 7.6 configuration for session prelaunch and linger

Source Citrix Blogs by By Andrzej Gołębiowski

XenApp and XenDesktop 7.6 session lingering explained

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
2. 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 

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.

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

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

Related Posts:

1. XenApp and XenDesktop 7.6 session prelaunch explained
2. StoreFront 2.6 mandatory store explained
3. XenApp and XenDesktop 7.6 connection leasing explained
4. New features in XenApp and XenDesktop 7.6
5. XenApp 6.5 load evaluator explained

By Andrzej Gołębiowski|

Session prelaunch is one of the set of features created to provide a better user experience working on XenApp and XenDesktop products. XenDesktop session prelaunch was reintroduced in version 7.6 – originally session prelaunch was available in XenApp 6.5 but was removed from the first version of XenDesktop 7.

Introduction 

The session prelaunch help all or specified users access applications quickly, by starting sessions before they are requested. By default session prelaunch is turned off and must be configured manually. In the default configuration each session starts (launches) when a user starts an application, and remains active until the last open application in the session closes. When this option is configured a session is waiting for a user and when the user starts an application prelaunched session is replaced with a regular session. If the user does not start an application (the prelaunched session is unused). We can configure the time when prelaunch session is created and for how long that session remains active. The configuration details are shown in section How to configure ? below.

Key considerations:

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

• Session prelaunch 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 prelaunch is available only for the machines must be running a VDA for Server OS, minimum version 7.6.
• Session prelaunch  is supported only when using Citrix Receiver for Windows. In Citrix Receiver 4.2 when you install the Single Sign-on (SSON) component, session prelaunch enabled by default.
• When using session prelaunch:
  • Physical client machines cannot use the suspend or hibernate power management functions.
  • Client machine users can lock their sessions but should not log off.

Licensing and resource implications

Prelaunched sessions consume a license, but only when connected. Unused prelaunched sessions disconnect after 15 minutes by default. This value can be configured in PowerShell (New/Set-BrokerSessionPreLaunch cmdlet). Optimal configuration balances the benefits of earlier application availability for users against the cost of keeping licenses in use and resources allocated.

Important note: You should carefully verify your licensing model before you enable session prelaunch for all users. This option is fine when you use 1:1 concurrent license or per user/desktop license. If you configure session prelaunch for all users and you have less licenses than total number of workstations you will hit your license limit just in first few minutes in the morning when users will logon to the network (prelaunch session will be created in the background for all users with citrix receiver installed on their computer even though they may not use a XenApp app at all.
If you have other than 1:1 license ratio you can consider to enable session prelaunch only for specified Active Directory groups. You can also try to fix possible problems using short prelaunch timeout – for not used prelaunched sessions or linger timeout to disconnect disconnected sessions but this could be only a workaround.

How to configure ?

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

Server side actions:

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
2. Enable and configure Session Prelaunch on XenDesktop 7.6 delivery group – to enable session prelaunch follow the steps below:
   • Open Citrix Studio
   • In the left pane select Delivery Groups
   • In the middle pane select the delivery group you want to modify
   • In the right  pane  (Action pane) click Edit Delivery Group
   • On the left side select Application Prelaunch and configure required settings. You can configure 2 behaviors:
     1. When prelaunch session will be created – Launch when user start an appliaction (no prelaunch) is default selection
     2. How long unused prelaunched sessions 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 – a configured timeout specifies the number of minutes, hours, or days an unused prelaunched session remains active. If you configure too short a timeout, prelaunched sessions will end before they provide the user benefit of quicker application access. If you configure too long a timeout, incoming user connections might be denied because the server doesn’t have enough resources.You cannot disable this timeout from Studio, but you can in the SDK (New/Set-BrokerSessionPreLaunch cmdlet). If you disable the timeout, it will not appear in the Studio display for that Delivery Group or in the Edit Delivery Group wizard.

Thresholds – automatically ending prelaunched sessions based on server load ensures that sessions remain open as long as possible, assuming server resources are available. Unused prelaunched sessions will not cause denied connections because they will be ended automatically when resources are needed for new user sessions.You can configure two thresholds: the average percentage load of all servers in the Delivery Group, and the maximum percentage load of a single server in the Delivery Group. When a threshold is exceeded, the sessions that have been in the prelaunch or 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 prelaunch sessions are started.)

The example is shown in Figure 2 below

3. Configure pass-through settings on client device  – in most cases this will be done via Group Policy. To configure this follow the steps below:
   1. Open Group Policy Editor
   2. Create a new group policy and switch to edit mode
   3. Browse to Computer Configuration -> Administrative Templates
   4. Right click and select Add/Remove templates
   5. Add dd the icaclient.adm this is located in the install location of Receiver “C:Program FilesCitrixICA ClientConfiguration”.
   6. Browse to Computer Configuration -> Administrative Templates -> Classic Administrative Templates -> User Authentication -> Local Username and Password
   7. Enable Local user name and password and configure it as it is shown in the Figure 3 below
   8. Link created group policy object to OU with client computers

Client side actions:

1. Install citrix receiver with Single Sign on – from the command line use Citrix Receiver with the /includeSSON flag.
2. Verify if the following registry key is enabled and set to true: HKLMSoftwareCitrixDazzleEnablePreLaunch. Based on the citrix blog article, starting from Citrix Receiver 4.2 session prelaunch should be enabled by default. If not enabled, use GPO or other method to enable and configure this registry setting.
3. Restart client computer

How to verify if session prelaunch is working  ?

In order to verify if session prelaunch is configured select the delivery group in Citrix Studio. The result is shown in the figure 4.

To display all session lingering settings powershell cmdlet Get-BrokerSessionPreLaunch can be used. The result is displayed in Figure 5.

In order to verify if session prelaunch is realy working is to use powershell cmdlet to display all sessions. Use powershell cmdlet get-brokersession to display all sessions with all details as it is shown in Figure 6. Not easy to read for 100 and more sessions

I would prefer to add some additional parameters to make the result more readable. Use the following command to display session information in more friendly layout:

Get-BrokerSession -SessionType Application -Property AppState, SessionState, Uid, UserName, ApplicationsInUse, DnsName, ReceiverName |Format-Table

The result is shown in Figure 7

Related Posts:

1. XenApp and XenDesktop 7.6 session lingering explained
2. StoreFront 2.6 mandatory store explained
3. XenApp and XenDesktop 7.6 connection leasing explained
4. New features in XenApp and XenDesktop 7.6
5. XenApp 7.5 Quick Installation Guide Part 4

By Andrzej Gołębiowski

Source: Citrix Website

The session prelaunch and session linger features help specified users access applications quickly, by starting sessions before they are requested (session prelaunch) and keeping application sessions active after a user closes all applications (session linger).

By default, session prelaunch and session linger are not used: a session starts (launches) when a user starts an application, and remains active until the last open application in the session closes.

Considerations:

• The Delivery Group must support applications, and the machines must be running a VDA for Server OS, minimum version 7.6.
• These features are supported only when using Citrix Receiver for Windows, and also require additional Receiver configuration. For instructions, search for “session prelaunch” in the eDocs content for your Receiver for Windows version.
• When using session prelaunch:
  • Physical client machines cannot use the suspend or hibernate power management functions.
  • Client machine users can lock their sessions but should not log off.
• Prelaunched and lingering sessions consume a license, but only when connected. Unused prelaunched and lingering sessions disconnect after 15 minutes by default. This value can be configured in PowerShell (New/Set-BrokerSessionPreLaunch cmdlet).
• Careful planning and monitoring of your users’ activity patterns are essential to tailoring these features to complement each other. Optimal configuration balances the benefits of earlier application availability for users against the cost of keeping licenses in use and resources allocated.
• You can also configure session prelaunch for a scheduled time of day in Receiver.

To enable session prelaunch:

1. Select Delivery Groups in the Studio navigation pane.
2. Select a Delivery Group, and then click Edit Delivery Group in the Actions pane.
3. On the Application Prelaunch page, enable session prelaunch by choosing when sessions should launch:
   • When a user starts an application. This is the default setting; session prelaunch is disabled.
   • When any user in the Delivery Group logs on to Receiver for Windows.
   • When anyone in a list of users and user groups logs on to Receiver for Windows. Be sure to also specify users or user groups if you choose this option.
   
4. A prelaunched session is replaced with a regular session when the user starts an application. If the user does not start an application (the prelaunched session is unused), the following settings affect how long that session remains active. For details about these settings, see How long unused prelaunched and lingering sessions remain active below.
   • When a specified time interval elapses. You can change the time interval (1-99 days, 1-2376 hours, or 1-142,560 minutes).
   • When the average load on all machines in the Delivery Group exceeds a specified percentage (1-99%).
   • When the load on any machine in the Delivery Group exceeds a specified percentage (1-99%).

   Recap: A prelaunched session remains active until one of the following events occurs: a user starts an application, the specified time elapses, or a specified load threshold is exceeded.

To enable session linger:

1. Select Delivery Groups in the Studio navigation pane.
2. Select a Delivery Group, and then click Edit Delivery Group in the Actions pane.
3. On the Application Lingering page, enable session linger by selecting the Keep sessions active until radio button.
   
4. Several settings affect how long a lingering session remains active if the user does not start another application. For details about these settings, see How long prelaunched and lingering sessions remain active below.
   • When a specified time interval elapses. You can change the time interval (1-99 days, 1-2376 hours, or 1-142,560 minutes).
   • When the average load on all machines in the Delivery Group exceeds a specified percentage (1-99%).
   • When the load on any machine in the Delivery Group exceeds a specified percentage (1-99%).

   Recap: A lingering session remains active until one of the following events occurs: a user starts an application, the specified time elapses, or a specified load threshold is exceeded.

How long unused prelaunched and lingering sessions remain active – There are several ways to specify how long an unused session remains active if 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 – A configured timeout specifies the number of minutes, hours, or days an unused prelaunched or lingering session remains active. If you configure too short a timeout, prelaunched sessions will end before they provide the user benefit of quicker application access. If you configure too long a timeout, incoming user connections might be denied because the server doesn’t have enough resources.

  You cannot disable this timeout from Studio, but you can in the SDK (New/Set-BrokerSessionPreLaunch cmdlet). If you disable the timeout, it will not appear in the Studio display for that Delivery Group or in the Edit Delivery Group wizard.

• Thresholds – Automatically ending prelaunched and lingering sessions based on server load ensures that sessions remain open as long as possible, assuming server resources are available. Unused prelaunched and lingering sessions will not cause denied connections because they will be ended automatically when resources are needed for new user sessions.

  You can configure two thresholds: the average percentage load of all servers in the Delivery Group, and the maximum percentage load of a single server in the Delivery Group. When a threshold is exceeded, the sessions that have been in the prelaunch or 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 prelaunch sessions are started.)

Servers with VDAs that have not registered with the Controller, and servers in maintenance mode are considered fully loaded. An unplanned outage will cause prelaunch and lingering sessions to be ended automatically to free capacity.