What is the best way to collect and transform output from multiple PowerShell threads? - multithreading

Question

I am new to PowerShell scripting and would like to do the following:
Given a list of config names and servers, return the values for the configs from each server.
Transform them in such a way to group them by config name, and not server.
Currently, I have a script that spawns one job per server and calls a script remotely on the server to return the list of configs for that server.
However, I do not know how to aggregate and transform the output from these jobs so that instead of getting config names by server, I would like to sort them by config name first, then server.
Current output:
Server1:
Config1 = 'abc'
Config2 = 'def'
Server2:
Config1 = 'xyz'
Config2 = '123'
Desired output:
Config1:
Server1 : 'abc'
Server2 : 'xyz'
Config2:
Server1 : 'def'
Server2 : '123'
I don't want to iterate over the config names because that would waste time in connecting to the server for every call. Therefore I'd like to iterate over the servers and do some kind of transformation.
I'm wondering if this is a matter of having each job return some kind of dictionary, then iterate over them after all the threads finish to transform?
Here is the code that calls the jobs:
$all_servers = #('server1', 'server2')
$config_names = #('config1', 'config2')
foreach($servername in $all_servers) {
Start-Job -FilePath C:\scripts\get_config_from_servers.ps1
-ArgumentList $servername,$config_names
}
Get-Job | Wait-Job
Get-Job | Receive-Job | Out-GridView
Here is the job script:
Param($servername,$config_names)
$session = Get-Session -computername $servername
-username $$$$
-pwd ####
try {
$sb = {
param($servername,$config_names)
$output = #{}
foreach ($cfg in $config_names) {
$config_value = Get-Config -configname $cfg
$output.Add("$servername : $cfg", "($config_value)")
}
write-host $output | Out-String
return $output | Out-String
}
$out = Invoke-Command -session $session
-ScriptBlock $sb
-ArgumentList $servername,$config_names
write-host $out
return $out
}
finally {
Remove-PSSession $session
}

Answer 1

Instead of making a hash table and converting to a string you could create some custom object in you job script just like this SO Question
Instead of this:
$output = #{}
foreach ($cfg in $config_names) {
$config_value = Get-Config -configname $cfg
$output.Add("$servername : $cfg", "($config_value)")
}
write-host $output | Out-String
return $output | Out-String
You could try something like this:
$output = New-Object System.Object
Add-Member -MemberType NoteProperty -Name Server -Value $servername -InputObject $output
foreach ($cfg in $config_names) {
$config_value = Get-Config -configname $cfg
Add-Member -MemberType NoteProperty -Name "Config$cfg" -Value $config_value -InputObject $output
}
write-host $output
return $output
I can't test this accurately as i'm not sure what Get-Config is but hopefully it should be enough to get you thinking.