Lab - Implement and monitor autoscaling of session hosts

Student lab manual

Lab dependencies

An Azure subscription you will be using in this lab.
A Microsoft Entra user account with the Owner or Contributor role in the Azure subscription you will be using in this lab and with the permissions sufficient to join devices to the Entra tenant associated with that Azure subscription.
The lab Deploy host pools and session hosts by using the Azure portal (Entra ID) completed
The lab Manage host pools and session hosts by using the Azure portal (Entra ID) completed
The lab Connect to session hosts (Entra ID) completed

Estimated Time

45 minutes

Lab scenario

You have an Azure Virtual Desktop environment which usage changes on regular basis. You want to minimize the cost by leveraging the autoscale scaling plans functionality.

Objectives

After completing this lab, you will be able to:

implement and evaluate Azure Virtual Desktop autoscaling

Lab files

None

Instructions

Exercise 1: Implement Azure Virtual Desktop autoscale scaling plans

The main tasks for this exercise are as follows:

Assign the required RBAC role to an Azure Virtual Desktop service principal
Stop and deallocate all session hosts
Adjust the host pool settings
Create a scaling plan
Evaluate the autoscaling functionality
Disable host pool autoscaling

Task 1: Assign the required RBAC role to an Azure Virtual Desktop service principal

Note: For autoscale plans to work, you need to grant the Azure Virtual Desktop service principal the permissions to manage the power state of the session host VMs. These permissions can be granted by using the built-in Desktop Virtualization Power On Off Contributor RBAC role. It is important to keep in mind that the role assignment must be performed at the subscription scope. Assigning this role at any level lower than your subscription, such as the resource group, host pool, or VM, will prevent autoscale from working properly.

Note: This role is different from the one (Desktop Virtualization Power On Contributor) used in the lab Manage host pools and session hosts by using the Azure portal (Entra ID), which was required to support the Start VM on Connect functionality.

If needed, from the lab computer, start a web browser, navigate to the Azure portal and sign in by providing credentials of a user account with the Owner role in the subscription you will be using in this lab.

Note: Use the credentials of the User1- account listed on the Resources tab on the right side of the lab session window.
From the lab computer, in the web browser displaying the Azure portal, start a PowerShell session in the Azure Cloud Shell.

Note: If prompted, in the Getting started pane, in the Subscription drop-down list, select the name of the Azure subscription you are using in this lab and then select Apply.
In the PowerShell session in the Azure Cloud Shell pane, run the following command to retrieve the value of the Id property of the Azure subscription you are using in this lab and store it in a variable $subId:
```
 $subId = (Get-AzSubscription).Id
```
Run the following command to create a $parameters variable, which stores a hash table that contains the values of the RBAC role definition name, Microsoft Entra application representing the Azure Virtual Desktop service principal, and the subscription scope:
```
 $parameters = @{
     RoleDefinitionName = "Desktop Virtualization Power On Off Contributor"
     ApplicationId = "9cdead84-a844-4324-93f2-b2e6bb768d07"
     Scope = "/subscriptions/$subId"
 }
```
Run the following command to create the RBAC role assignment:
```
 New-AzRoleAssignment @parameters
```
Close the Cloud Shell pane.

Task 2: Stop and deallocate all session hosts

Note: To evaluate the autoscaling functionality, you will stop and deallocate all of the session hosts in the Azure Virtual Desktop environment.

From the lab computer, in the web browser displaying the Azure portal, search for and select Azure Virtual Desktop and, on the Azure Virtual Desktop page, in the vertical menu bar, in the Manage section, select Host pools.
On the Azure Virtual Desktop | Host pools page, in the list of host pools, select az140-21-hp1.
On the az140-21-hp1 page, in the in the vertical menu bar, in the Manage section, select Session hosts.
On the az140-21-hp1 | Session hosts page, select the checkbox next to each session host name and then select Stop.
When prompted to confirm, in the Stop session hosts pop-up window, select Stop.

Note: You might need to select the ellipsis (...) icon in the toolbar to display the Stop button.

Note: Do not wait until the session hosts are stopped and deallocated, but instead proceed to the next task. Stopping and deallocating session hosts might take about 2 minutes.

Task 3: Adjust the host pool settings

Note: When using autoscale for pooled host pools, you must have a configured MaxSessionLimit parameter for that host pool. In this lab, you will set it artificially low in order to facilitate illustrating the autoscaling functionality.

From the lab computer, in the web browser displaying the Azure portal, on the az140-21-hp1 page, in the Settings section, select Properties.
On the az140-21-hp1|Properties page, in the Max session limit text box, enter 1.
On the az140-21-hp1|Properties page, select Save.

Task 4: Create a scaling plan

From the lab computer, in the web browser displaying the Azure portal, search for and select Azure Virtual Desktop, on the Azure Virtual Desktop page, in the Manage section of the vertical navigation menu, select Scaling plans.
On the Azure Virtual Desktop | Scaling plans page, select + Create.

On the Basics tab of the Create a scaling plan page, specify the following settings and select Next: Schedules:

Setting	Value
Subscription	the name of the Azure subscription you are using in this lab
Resource group	the name of a new resource group az140-412e-RG
Scaling plan name	az140-scalingplan412e
Region	the name of the Azure region where you deployed the Azure Virtual Desktop environment
Friendly name	az140-scalingplan412e
Time zone	the local time zone of the Azure region where you deployed the Azure Virtual Desktop environment
Host pool type	Pooled

Note: Leave the Exclusion tag property not set. In general, you can use this feature to exclude Azure VMs with arbitrarily set tags from autoscaling.

On the Schedule tab, select + Add schedule.

Note: Schedules allow you to define ramp-up hours, peak hours, ramp-down hours, and off-peak hours for week days and specify autoscaling triggers. Scaling plan must include an associated schedule for at least one day of the week.

On the General tab of the Add a schedule pane, adjust the default configuration to match the following settings and then select Next:

Setting	Value
Time zone	the local time zone of your Azure Virtual Desktop environment (based on the region you selected earlier in this task)
Schedule name	week_schedule
Repeat on	7 selected (select all days of the week)

Note: The schedule effectively covers every day of the week, which will facilitate evaluating outcome of autoscaling.

On the Ramp-up tab of the Add a schedule pane, adjust the default configuration to match the following settings and then select Next:

Setting	Value
Start time (12 hour system)	your current time minus 1 hour
Load balancing algorithm	Breadth-first
Minimum percentage of hosts (%)	30
Capacity threshold (%)	60

Note: For pooled host pools, autoscale ignores existing load-balancing algorithms in your host pool settings, and instead applies load balancing based on your schedule configuration.

Note: The Minimum percentage of hosts setting designates the minimum percentage of session host virtual machines to start for ramp-up and peak hours. For example, if Minimum percentage of hosts is specified as 30% and total number of session hosts in your host pool is 3, autoscale will ensure a minimum of 1 session host is available to accept user connections.

Note: Autoscale rounds up to the nearest whole number.

Note: The Capacity threshold setting is the percentage of used host pool capacity that will be considered to evaluate whether to turn on/off virtual machines during the ramp-up and peak hours. For example, if capacity threshold is specified as 60% and your host pool capacity is 1 session (with one host running), autoscale will turn on additional session hosts once the load of the host pool exceeds 60% (it’s 100% in this case).

On the Peak hours tab of the Add a schedule pane, adjust the default configuration to match the following settings and then select Next:

Setting	Value
Start time (12 hour system)	your current time plus 1 hour
Load balancing algorithm	Depth-first
Capacity threshold (%)	60

Note: The Capacity threshold (%) setting is shared between the Ramp-up and Peak hours settings.

On the Ramp-down tab of the Add a schedule pane, adjust the default configuration to match the following settings and then select Next:

Setting	Value
Start time (12 hour system)	your current time plus 2 hours
Load balancing algorithm	Depth-first
Minimum percentage of active hosts (%)	10
Capacity threshold (%)	80
Force logoff users	No
Stop VMs when	VMs have no active or disconnected sessions

Note: The Minimum percentage of active hosts (%) setting designates the minimum percentage of session host virtual machines that you would like to get to for ramp-down and off-peak hours. For example, if Minimum percentage of active hosts (%) is set to 10% and total number of session hosts in your host pool is 3, autoscale will ensure a minimum of 1 session host is available to take user connections.

Note: The Capacity threshold (%) setting designates the percentage of used host pool capacity that will be considered to evaluate whether to turn off virtual machines during the ramp-down and off-peak hours. For example, with 1 user connection and 3 hosts running, if capacity threshold is specified as 80%, autoscale would turn off 1 host (resulting in 50% used host pool capacity).

Note: In general, autoscale will stop and deallocate session hosts according to the following rules:

The used host pool capacity is below the capacity threshold.
Turning off session hosts will not result in exceeding the capacity threshold.
Autoscale only turns off session hosts with no user sessions on them, unless the scaling plan is in ramp-down phase and you’ve enabled the setting to force user logoff.
Pooled autoscale will not turn off session hosts in the ramp-up phase to ensure that user experience is not impacted.

On the Off-peak hours tab of the Add a schedule pane, adjust the default configuration to match the following settings and then select Add:

Setting	Value
Start time (12 hour system)	your current time plus 3 hours
Load balancing algorithm	Depth-first
Capacity threshold (%)	80

Note: The Capacity threshold setting is shared between the Ramp-down and Off-peak hours settings.

Back on the Schedule tab of the Create a scaling plan page, select Next: Host pool assignments.
On the Host pool assignments tab, in the Select host pool drop-down list, select az140-21-hp1, ensure that Enable autoscale checkbox is selected, and then select Review + create.
On the Review + Create page, select Create.

Note: Wait for autoscale configuration to complete. This typically takes just a few seconds.

Task 5: Evaluate the autoscaling functionality

Note: You will start by evaluating the Ramp-up settings.

From the lab computer, in the web browser displaying the Azure portal, search for and select Azure Virtual Desktop and, on the Azure Virtual Desktop page, in the vertical menu bar, in the Manage section, select Host pools.
On the Azure Virtual Desktop | Host pools page, in the list of host pools, select az140-21-hp1.
On the az140-21-hp1 page, in the in the vertical menu bar, in the Manage section, select Session hosts.
On the az140-21-hp1 | Session hosts page, review the values of the Power state setting of session hosts and verify that one of them is listed as Running.

Note: You might need to wait a couple of minutes before the first session hosts reaches the Running state.

Note: This is expected, since according to the Ramp-up settings of the newly created scaling plan, at least one session host should be always online. At this point, the host pool capacity is 1 (since there is only 1 host running), but the used host pool capacity is 0%, since there are no user connections.

Note: Next, you will evaluate the Ramp-up and Peek hours capacity threshold setting by launching a single user session. We can evaluate this even outside of Peek hours window, since the two stages share the same capacity threshold.
From the lab computer, start the Microsoft Remote Desktop client.
On the lab computer, in the Remote Desktop client window, select Subscribe and, when prompted, sign in with the credentials of the User2 Entra ID user account which you can locate on the Resources tab in the right pane of the lab interface window.
Ensure that the Remote Desktop page displays four icons, including Microsoft Word, Microsoft Excel, Microsoft PowerPoint, and Command Prompt.
Double-click the Command Prompt icon.
When prompted to sign in, in the Windows Security dialog box, enter the password of the Microsoft Entra user account you used to connect to the target Azure Virtual Desktop environment.
Verify that a Command Prompt window appears shortly afterwards.

Note: At this point, the used host pool capacity is 100%, which is greater than the capacity threshold (%60). This should result in autoscaling turning on another host, which will bring the used host pool capacity to 50%. Since this is below the capacity threshold, the third host will remain stopped/deallocated. You will verify this next.
From the lab computer, switch to the web browser displaying the Azure portal.
On the az140-21-hp1 | Session hosts page, select Refresh, review the values of the Power state setting of session hosts, and verify that now two of them are listed as Running.

Note: Next, you will evaluate the Ramp-down capacity threshold setting by adjusting its time window.
On the az140-21-hp1 | Session hosts page, in the vertical navigation menu, in the Settings section, select Scaling plans and then, on the Scaling plans page, select az140-scalingplan412e.
On the az140-scalingplan412e page, in the vertical navigation menu, in the Settings section, select Schedules and then select week_schedule.
In the week_schedule pane, navigate to the Ramp-down tab and adjust the value of the Start time (12 hour system) setting to any time between the Start time (12 hour system) of the Peek hours phase and your current time.

Note: You might need to adjust the value of Start time (12 hour system) of the Peek hours phase.
In the week_schedule pane, navigate to the Off-peek hours tab and select Save.
Switch to the Command Prompt window representing the only RDP session to the host pool and, at the Command Prompt, enter the following and press the Enter key:
```
 logoff
```
From the lab computer, in the web browser displaying the Azure portal, search for and select Azure Virtual Desktop and, on the Azure Virtual Desktop page, in the vertical menu bar, in the Manage section, select Host pools.
On the Azure Virtual Desktop | Host pools page, in the list of host pools, select az140-21-hp1.
On the az140-21-hp1 page, in the in the vertical menu bar, in the Manage section, select Session hosts.
On the az140-21-hp1 | Session hosts page, review the values of the Power state setting of session hosts and verify that now only one of them is listed as Running.

Task 6: Disable host pool autoscaling

Note: To ensure that the autoscaling configuration will not affect other labs, you will remove the host pool assignment of the scaling plan you implemented in this lab.

From the lab computer, in the web browser displaying the Azure portal, search for and select Azure Virtual Desktop, on the Azure Virtual Desktop page, in the Manage section of the vertical navigation menu, select Scaling plans, and then, on the Scaling plans page, select az140-scalingplan412e.
On the az140-scalingplan412e page, in the Manage section, select Host pool assignments.
On the az140-scalingplan412e | Host pool assignments page, select az140-21-hp1, then select Unassign and, when prompted to confirm, in the Unassign host pool dialog box, select Unassign.