Powershell 3.0 - Workflows - Limit number of parallel execution

Question

I am cloning VMs on ESX server from template. Simplified code looks like this:

Workflow Create-VM {
  $List = 1..500
  foreach -parallel ($Elem in $List)
  {
            


        

Answer 1

Just wanted to add this detail, ThrottleLimit switch mentioned above is available in Powershell v4.0, its not available in v3.0. We have a mix of 2.0 and 3.0 servers

Answer 2

A trivial solution is to divide the list into smaller chunks and use that as input for parallel foreach. Like so,

Workflow Create-VM {
  $List = 1..500
  # Calclulate indexes to get elements 0,3; 4,7; 8,11 and so on
  # Use the .. operator to extract those elements from $list and pass
  # 'em to foreach -parallel processing part
  for($i=0;$i -le $List.Count-4; $i+=4) { 
    foreach -parallel ($Elem in $list[$i..($i+3)]) {
      # Create VM ...
      # Configure created VM ..
    } 
  }
}

Answer 3

There is an option to limit the number of parallel processes in a foreach-parallel loop using -throttlelimit N. It's great for reducing the parallelism, but if you try a high number the system may still limit you to 5, depending on all your software versions (YAY! Microsoft consistency). I know the question is old, but since it came up on Google without a decent answer, I thought I'd chime in.

Workflow Create-VM {
  $List = 1..500
  foreach -parallel -throttlelimit 4 ($Elem in $List)
  {
      # Create VM ...
      # Configure created VM ..
  }
}

Create-VM