Multi-threading with PowerShell - event-log

Question

I have done lots of reading about multi-threading in PowwerShell with Get-Job and Wait-Job but still cant seem to work it out.
Eventually, I will have this as a GUI based script to run and don't want my GUI to freeze up while its doing its task.
The script is looking for Event Logs of my Domain Controllers and then getting the details I want, then outputting them, it works like I need it to.
I can start a job using Invoke-Command {#script goes here} -ComputerName ($_) -AsJob -JobName $_ and the jobs run.
Script below:
Clear-Host
Get-Job | Remove-Job
(Get-ADDomainController -Filter *).Name | ForEach-Object {
Invoke-Command -ScriptBlock {
$StartTime = (Get-Date).AddDays(-4)
Try{
Get-WinEvent -FilterHashtable #{logname='Security'; id=4740;StartTime=$StartTime} -ErrorAction Stop `
| Select-Object * | ForEach-Object {
$Username = $_.Properties[0].Value
$lockedFrom = $_.Properties[1].Value
$DC = $_.Properties[4].Value
$Time = $_.TimeCreated
Write-Host "---------------------------------------------"
Write-Host $Username
Write-Host $lockedFrom
Write-Host $DC
Write-Host $Time
Write-Host "---------------------------------------------"
}#ForEach-Object
}catch [Exception] {
If ($_.Exception -match "No events were found that match the specified selection criteria") {
Write-Host "No events for locked out accounts." -BackgroundColor Red
}#If
}#Try Catch
} -ComputerName ($_) -AsJob -JobName $_ | Out-Null # Invoke-Command
}#ForEach-Object
Currently I have a While loop to tell me its waiting then to show me the result:
(Get-ADDomainController -Filter *).Name | ForEach-Object {
Write-Host "Waiting for: $_."
While ($(Get-Job -Name $_).State -ne 'Completed') {
#no doing anything here
}#While
Receive-Job -Name $_ -Keep
}#ForEach-Object
#clean up the jobs
Get-Job | Remove-Job
Thinking of my GUI (to be created), I will have a column for each Domain Controller and showing results under each heading, how do make it not freeze my GUI and show the results when they arrive?
I know its been asked a few times, but the examples I cant work out.

Answer 1

I would avoid Start-Job for threading - for efficiency try a runspace factory.
This is a basic setup which could be useful (I also have PS 4.0), and open to suggestions/improvements.
$MaxThreads = 2
$ScriptBlock = {
Param ($ComputerName)
Write-Output $ComputerName
#your processing here...
}
$runspacePool = [RunspaceFactory]::CreateRunspacePool(1, $MaxThreads)
$runspacePool.Open()
$jobs = #()
#queue up jobs:
$computers = (Get-ADDomainController -Filter *).Name
$computers | % {
$job = [Powershell]::Create().AddScript($ScriptBlock).AddParameter("ComputerName",$_)
$job.RunspacePool = $runspacePool
$jobs += New-Object PSObject -Property #{
Computer = $_
Pipe = $job
Result = $job.BeginInvoke()
}
}
# wait for jobs to finish:
While ((Get-Job -State Running).Count -gt 0) {
Get-Job | Wait-Job -Any | Out-Null
}
# get output of jobs
$jobs | % {
$_.Pipe.EndInvoke($_.Result)
}