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Dmitry_Popov's avatar
Dmitry_Popov
Copper Contributor
May 05, 2020

The strange behavior of PowerShell script in disconnected session

Hello!

Could you please explain the strange behavior of PowerShell script in disconnected session?
During execution of following script PowerShell console hangs after first 32 items been processed and I have no other option than to destroy its process forcibly.

 

 

$computers = (Get-ADComputer -Filter *).name | select -First 35
Invoke-Command -ComputerName $computers -InDisconnectedSession -ScriptBlock {
            $out = $env:COMPUTERNAME
            Start-Sleep -Seconds 10
            return $out
}

 

All listed sessions are in busy state.

If number of selected items is limited by 32 or less everything works fine. Also helps using ThrottleLimit argument.

 

$computers = (Get-ADComputer -Filter *).name | select -First 35
Invoke-Command -ComputerName $computers -InDisconnectedSession -ThrottleLimit $computers.Count -ScriptBlock {
            $out = $env:COMPUTERNAME
            Start-Sleep -Seconds 10
            return $out
}

 


I guess somehow it could be connected to that default number of simultaneous sessions are limited by 32.

Can you please explain how to correctly work with disconnected sessions if its number a lot much more than 32?

Windows PowerShell

4 Replies

  • Animesh Joshi's avatar
    Animesh Joshi
    Brass Contributor
    May 05, 2020
    you're using -inDisconnectedSession parameter which, disconnects the sessions as soon as it starts the command.
    Surely you can use invoke-command on more than 32 computers.
    Look at example 7 and 18 on https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/invoke-command?view=powershell-7
    • Dmitry_Popov's avatar
      Dmitry_Popov
      Copper Contributor
      May 06, 2020

      Animesh Joshi 

      Example 7 without the inDisconnectedSession parameter.
      Example 18 hangs with busy status if the number of computers is more than 32.
      I found two working crutches for myself, but I would like to understand why it does not work as expected.

      Crutch 1

       

      $computers = (Get-ADComputer -Filter *).name | select -First 35
Invoke-Command -ComputerName $computers -InDisconnectedSession -ThrottleLimit $computers.Count -ScriptBlock {
            $out = $env:COMPUTERNAME
            Start-Sleep -Seconds 10
            return $out
}

       

       Crutch 2

       

      $computers = (Get-ADComputer -Filter *).name | select -First 35
foreach ($item in $computers)
{
	Invoke-Command -ComputerName $item -InDisconnectedSession -ScriptBlock {
            $out = $env:COMPUTERNAME
            Start-Sleep -Seconds 10
            return $out
	}
}

       

      • Mike Shivtorov's avatar
        Mike Shivtorov
        Copper Contributor
        May 08, 2020

        Dmitry_Popov 
        Just use "ThrottleLimit" parameter to specify the maximum number of concurrent connections. Its default value is 32.

        For example, 100 connections at a time:

        Invoke-Command -ComputerName $computers -InDisconnectedSession -ThrottleLimit 100 -ScriptBlock { hostname }

         

        Don't make too many concurrent connections.

        In your latest comment you use "-ThrottleLimit $computers.Count" - it might be too high depending on number of computers in your domain. I guess a hundred or two of concurrent sessions should be more than enough.

         

        Get-Help Invoke-Command -Parameter ThrottleLimit