I have found that the session hosts often end up reporting a status of ‘Needs Assistance’. This can be caused by updates having been applied that require a reboot to complete…and other unknown issues. Often a reboot will sort them out. So I developed a simple script to assist.

The following script will allow you to specifiy the only the VM’s in a Host Pool and only those that ‘Need Assistance’ and that have no active sessions on too….or not!

Save the full script to a file called RebootHosts.ps1

<#PSScriptInfo
.VERSION 1.0
.GUID b053571a-b9f4-445d-ac05-45e184cf6f90
.AUTHOR Nicholas Rogoff
.RELEASENOTES

#>
<#
.SYNOPSIS
  Reboots VMs in a HostPool
.DESCRIPTION
  This will iterate through the VMs registered to a host pool and reboot them. 
.NOTES
  Version:        1.0
  Author:         Nicholas Rogoff
  Creation Date:  2020-09-03
  Purpose/Change: Initial script development

.EXAMPLE
  .\RebootHosts.ps1 -HostPoolName "my-host-pool" -HostPoolResourceGroupName "my-host-pool-rg" -OnlyDoIfNeedsAssistance -SkipIfActiveSessions
#>

#---------------------------------------------------------[Script Parameters]------------------------------------------------------
[CmdletBinding()]
Param (
    #Script parameters go here
    [Parameter(mandatory = $true)]
    [string]$HostPoolName,

    [Parameter(mandatory = $true)]
    [string]$HostPoolResourceGroupName,
    
    [Parameter(mandatory = $false)]
    [switch]$SkipIfActiveSessions,

    [Parameter(mandatory = $false)]
    [switch]$OnlyDoIfNeedsAssistance
)

#---------------------------------------------------------[Initialisations]--------------------------------------------------------

#Set Error Action to Silently Continue
$ErrorActionPreference = 'SilentlyContinue'

#----------------------------------------------------------[Declarations]----------------------------------------------------------

#Any Global Declarations go here

#-----------------------------------------------------------[Functions]------------------------------------------------------------


#-----------------------------------------------------------[Execution]------------------------------------------------------------

Write-Output "Starting to Enable Boot Diagnostics for VMs in Host Pool $HostPoolName ..."
if ($OnlyDoIfNeedsAttention) {
    Write-Output "!! Only hosts flagged as 'Needs Assistance' will be rebooted !!"
}
if ($SkipIfActiveSessions) {
    Write-Output "!! Only hosts with zero sessions will be rebooted !!"
}

$rebooted = 0
$skippedSessions = 0
$skippedOK = 0
$shutdown = 0

$sessionHosts = Get-AzWvdSessionHost -ResourceGroupName $HostPoolResourceGroupName -HostPoolName $HostPoolName
foreach ($sh in $sessionHosts) {
    

    # Name is in the format 'host-pool-name/vmname.domainfqdn' so need to split the last part
    $VMName = $sh.Name.Split("/")[1]
    $VMName = $VMName.Split(".")[0]
    
    $Session = $sh.Session
    $Status = $sh.Status
    $UpdateState = $sh.UpdateState
    $UpdateErrorMessage = $sh.UpdateErrorMessage

    Write-output "=== Starting Reboot for VM: $VMName"
    Write-output "Session: $Session"
    Write-output "Status: $Status"
    Write-output "UpdateState: $UpdateState"
    Write-output "UpdateErrorMessage: $UpdateErrorMessage"

    if ($Status -ne "Unavailable") {
        if ($Status -ne "NeedsAssistance" -and $OnlyDoIfNeedsAssistance ) {
            $skippedOK += 1
            Write-output "!! The VM '$VMName' is not in 'Needs Assistance' state, so will NOT be rebooted. !!"       
        }
        elseif ($SkipIfActiveSessions -and $Session -gt 0) {
            $skippeSessions += 1
            Write-output "!! The VM '$VMName' has $Session session(s), so will NOT be rebooted. !!"       
        }
        else {
            $rebooted += 1
            Restart-AzVM -ResourceGroupName $HostPoolResourceGroupName -Name $VMName
            Write-output "=== Reboot initiated for VM: $VMName"       
        }
    }
    else {
        $shutdown += 1
        Write-output "!! The VM '$VMName' must be started in order to reboot it. !!"       
    }

}

Write-Output ""
Write-Output "============== Completed =========================="
Write-Output "Skipped due Not needing attention: $skippedOK"
Write-Output "Skipped due to active sessions: $skippedSessions"
Write-Output "Host not started: $shutdown"
Write-Output "Rebooted: $rebooted"
Write-Output "==================================================="

You will need to log in to Azure and select your subscription in the normal way using:

Login-AzAccount
Select-AzSubscription "my-subscription"

You can then simply run the script as follows:

.\RebootHosts.ps1 -HostPoolName "my-host-pool" -HostPoolResourceGroupName "my-host-pool-rg" -OnlyDoIfNeedsAssistance -SkipIfActiveSessions