deployNewImage.ps1

param (
    [string]$projectId = $(throw "-projectId is required.")
)
Update-AzConfig -DisplayBreakingChangeWarning $false | out-null
$ErrorActionPreference = "Stop"
$rgName = $projectId + "-RG"
$hostPool = $projectId + "-HP"
$location = "westus"

function Show-PoolHosts{
    ""
    $currentHosts = Get-AzWvdSessionHost -ResourceGroupName $rgName -HostPoolName $hostPool
    $format = "{0,-35}{1,-13}{2,-10}{3,-15}{4}"
    $format -f "Name", "Status", "Sessions", "Image Version", "VM Power State"
    foreach ($ahost in $currentHosts){ 
        $vmPowerState = (Get-AzVM -ResourceId $ahost.ResourceId -Status).Statuses[1].Code
        $imgVer = (Get-AzVM -ResourceId $ahost.ResourceId).StorageProfile.ImageReference.ExactVersion
        $format -f $ahost.Name, $ahost.Status, $ahost.Session, $imgVer, $vmPowerState 
    }
    ""
}

Show-PoolHosts

#
# Determine what is the latest golden image version in the Gallery.
#
$imageGalery = $projectId + "_Galery"
$imgVersions = Get-AzGalleryImageVersion -ResourceGroupName $rgName -GalleryName $imageGalery -GalleryImageDefinitionName Windows11MultiUser-VDI-Apps
$latestImage = $imgVersions | select -first 1
foreach ($ver in $imgVersions){
    if ($latestImage.PublishingProfile.PublishedDate -lt $ver.PublishingProfile.PublishedDate){
        $latestImage = $ver
    }
}

#
# Determine how many of the current hosts were deployed using and older image version.
#
$activeHosts = Get-AzWvdSessionHost -ResourceGroupName $rgName -HostPoolName $hostPool | where {$_.AllowNewSession -eq $true} 
foreach ($ahost in $activeHosts){ 
        $vm = Get-AzVM -ResourceId $ahost.ResourceId
        "Current SessionHost version: " + $vm.StorageProfile.ImageReference.ExactVersion
        "Most recent version name: " + $latestImage.name
        if ($vm.StorageProfile.ImageReference.ExactVersion -ne $latestImage.name){
            $hostsToReplace += 1
        }
}

#
# If there are no hosts created with an older image version, end the script.
#
if ( $hostsToReplace -eq 0 ){ 
    "All host are at the latest image version"
    Exit 
}
"Number of hosts to replace: " + $hostsToReplace

#
# Get the information required to deploy new hosts, i.e, Pool registration key, VNet info, Username and Password
#
$registrationInfo = New-AzWvdRegistrationInfo `
                        -ResourceGroupName $rgName `
                        -HostPoolName $hostPool `
                        -ExpirationTime $((get-date).ToUniversalTime().AddDays(1).ToString('yyyy-MM-ddTHH:mm:ss.fffffffZ'))

$Vnet = Get-AzVirtualNetwork -Name "VDIVnet" -ResourceGroupName $rgName

#
# Grant KeyVault access to the current public IP and retrieve the VDI host username and password, and remove access when done.
#
$vault = $projectId + "-KV"
$pubIp = (Invoke-WebRequest -uri "https://api.ipify.org/").Content
Add-AzKeyVaultNetworkRule -VaultName $vault -IpAddressRange $pubIp
$vdiHostAdminUsername = Get-AzKeyVaultSecret -VaultName $vault -Name vdiHostAdminUsername -AsPlainText
$textPassword = Get-AzKeyVaultSecret -VaultName $vault -Name vdiHostAdminPassword -AsPlainText
Remove-AzKeyVaultNetworkRule -VaultName $vault -IpAddressRange $pubIp

$vdiHostAdminPassword = ConvertTo-SecureString $textPassword -AsPlainText -Force
$Credential = New-Object System.Management.Automation.PSCredential ($vdiHostAdminUsername, $vdiHostAdminPassword);

$justId = $projectId -replace "[^0-9]" , ''

#
# Include the image version number in the vm name.
#
$vmName = "sh" + $justId + "v" + $latestImage.name.Replace(".","") + "-"

#
# Create as many hosts as there are currently with dated image versions.
#
for($i = 1;$i -le $hostsToReplace;$i++)
{
    "Deploying host " + $i + " of " + $hostsToReplace
    $newVMName = $vmName + $i
    $NICName = $newVMName + "VMNic"
    $NIC = New-AzNetworkInterface -Name $NICName -ResourceGroupName $rgName -Location $Location -SubnetId $Vnet.Subnets[0].Id

    $VM = New-AzVMConfig -VMName $newVMName -VMSize "Standard_DS1_v2" -IdentityType SystemAssigned
    $VM = Set-AzVMOperatingSystem -VM $VM -Windows -ComputerName $newVMName -Credential $Credential -ProvisionVMAgent -EnableAutoUpdate
    $VM = Set-AzVMOSDisk -VM $VM -DeleteOption Delete -CreateOption FromImage
    $VM = Set-AzVMBootDiagnostic -VM $VM -Disable
    $VM = Add-AzVMNetworkInterface -VM $VM -Id $NIC.Id -DeleteOption Delete
    $VM = Set-AzVMSourceImage -VM $VM -Id $latestImage.id

    "Deploying VM " + $newVMName
    New-AzVM -ResourceGroupName $rgName -Location $location -VM $VM -LicenseType Windows_Client -DisableBginfoExtension

    "Joining VM " + $newVMName + " to AAD"
    Set-AzVMExtension `
        -ResourceGroupName $rgName `
        -VMName $newVMName `
        -Name  "AADLoginForWindows" `
        -Location $VM.Location `
        -Publisher "Microsoft.Azure.ActiveDirectory" `
        -Type "AADLoginForWindows" `
        -TypeHandlerVersion "0.4"
    
    "Adding VM " + $newVMName + " to Host Pool"
    $cmdResult = Invoke-AzVMRunCommand `
                    -ResourceGroupName $rgName `
                    -Name $newVMName `
                    -CommandId 'RunPowerShellScript' `
                    -ScriptPath 'setWVDClient.ps1' `
                    -Parameter @{registrationtoken = $registrationInfo.Token}

    $cmdResult.Value[0].Message
}

#
# Disable and deallocate previous-version hosts.
#
foreach ($shost in $activeHosts){ 
        $vm = Get-AzVM -ResourceId $shost.ResourceId
        if ($vm.StorageProfile.ImageReference.ExactVersion -ne $latestImage.name){
            "Disabling new sessions on VM: " + $vm.Name
            Update-AzWvdSessionHost -ResourceGroupName $rgName `
                            -HostPoolName $hostPool `
                            -Name $vm.Name `
                            -AllowNewSession:$false `
                            | select Name, Session, Status, AllowNewSession | ft

            if ($shost.Session -eq 0){ 
                "Stopping VM: " + $vm.Name
                Stop-AzVM -Id $vm.Id -Force
            }
        }
}

Show-PoolHosts