How to execute a PowerShell function several times in parallel?

Question

I'm not sure whether to call this a need for multi-threading, job-based, or async, but basically I have a Powershell script function that takes several parameters and I need to call it several times with different parameters and have these run in parallel.

Currently, I call the function like this:

Execute "param1" "param2" "param3" "param4" 

How can I call this multiple times without waiting for each call to Execute return to the caller?

Currently I'm running v2.0 but I can update if necessary

EDIT: here's what I have so far, which doesn't work:

$cmd = {     param($vmxFilePath,$machineName,$username,$password,$scriptTpath,$scriptFile,$uacDismissScript,$snapshotName)     Execute $vmxFilePath $machineName $username $password $scriptTpath $scriptFile $uacDismissScript $snapshotName }  Start-Job -ScriptBlock $cmd -ArgumentList $vmxFilePath, $machineName, $username $password, $scriptTpath, $scriptFile, $uacDismissScript, $snapshotName 

I get an error:

cannot convert 'system.object[]' to the type 'system.management.automation.scriptblock' required by parameter 'initializationscript'. specified method is not supported

EDIT2: I've modified my script but I still get the error mentioned above. Here's my mod:

$cmd = {     param($vmxFilePath,$machineName,$username,$password,$scriptTpath,$scriptFile,$uacDismissScript,$snapshotName)     Execute $vmxFilePath $machineName $username $password $scriptTpath $scriptFile $uacDismissScript $snapshotName }  Start-Job -ScriptBlock $cmd -ArgumentList $vmxFilePath, $machineName, $username $password, $scriptTpath, $scriptFile, $uacDismissScript, $snapshotName 

Answer 1

No update necessary for this. Define a script block and use Start-Job to run the script block as many times as necessary. Example:

$cmd = {   param($a, $b)   Write-Host $a $b }  $foo = "foo"  1..5 | ForEach-Object {   Start-Job -ScriptBlock $cmd -ArgumentList $_, $foo } 

The script block takes 2 parameters $a and $b which are passed by the -ArgumentList option. In the example above, the assignments are $_ → $a and $foo → $b. $foo is just an example for a configurable, but static parameter.

Run Get-Job | Remove-Job at some point to remove the finished jobs from the queue (or Get-Job | % { Receive-Job $_.Id; Remove-Job $_.Id } if you want to retrieve the output).

Answer 2

Here's a quick bogus scriptblock for the purpose of testing:

$Code = {     param ($init)     $start = Get-Date     (1..30) | % { Start-Sleep -Seconds 1; $init +=1 }     $stop = Get-Date     Write-Output "Counted from $($init - 30) until $init in $($stop - $start)." } 

This scriptblock can then be passed on to Start-Job, with for example 3 parameters (10, 15, 35)

$jobs = @() (10,15,35) | % { $jobs += Start-Job -ArgumentList $_ -ScriptBlock $Code }  Wait-Job -Job $jobs | Out-Null Receive-Job -Job $jobs 

This creates 3 jobs, assign them to the $jobs variable, runs them in parallel and then waits for these 3 jobs to finish, and retrieves the results:

Counted from 10 until 40 in 00:00:30.0147167. Counted from 15 until 45 in 00:00:30.0057163. Counted from 35 until 65 in 00:00:30.0067163. 

This did not take 90 seconds to execute, only 30.

One of the tricky parts is to provide -Argumentlist to Start-Job, and include a param() block inside the ScriptBlock. Otherwise, your values are never seen by the scriptblock.