Cannot make scriptblocks as a parameters executes in parallel

[vors]

If you run this line, it will take more then 3 seconds.

@({sleep 1; 1}, {sleep 1; 2}, {sleep 1; 3}) | Invoke-Parallel { return $_.Invoke() }

One of the things that can be really cool: make Invoke-Parallel work with pester tests. So I can pass describe blocks as an -InputObject

[RamblingCookieMonster]

Ahh, cool idea!

Looking at verbose output, the actual runtime is ~ .08 seconds for each. It looks like the hangup is when we call begininvoke():

$temp.Runspace = $powershell.BeginInvoke()

If I step through manually, I can reproduce this.

#Set things up
    $Throttle = 20
    $ScriptBlock = $ExecutionContext.InvokeCommand.NewScriptBlock("param(`$_, `$parameter)`r`n" + {$_.invoke()}.ToString()) 
    $object = {start-sleep -Seconds 10; "boo!"}

    $sessionstate = [System.Management.Automation.Runspaces.InitialSessionState]::CreateDefault()
    $runspacepool = [runspacefactory]::CreateRunspacePool(1, $Throttle, $sessionstate, $Host)
    $runspacepool.Open() 

    $powershell = [powershell]::Create()
    [void]$PowerShell.AddScript($ScriptBlock).AddArgument($object).AddArgument($parameter)
    $powershell.RunspacePool = $runspacepool

#I get a delay here...
    $rs = $powershell.BeginInvoke()

[RamblingCookieMonster]

This is a bit out of my wheelhouse, but this might help identify the root cause:

Measure-command { @({sleep 5; 1}, {sleep 5; 2}, {sleep 5; 3}) | Invoke-Parallel { [scriptblock]::Create( $_ ).invoke() } }

Returns in expected ~ 5 seconds.

Measure-command { @({sleep 5; 1}, {sleep 5; 2}, {sleep 5; 3}) | Invoke-Parallel {  $x = $_.psobject.copy(); $x.invoke() } }

Returns in unexpected ~ 15 seconds.

[vors]

@lzybkr comment:
If you call [ScriptBlock]::Create - the script block doesn't know it's runspace.
If you use { } - then it does, and will always run on that runspace.