Beginning parallel processing in PowerShell

Here’s a template (of sorts) that should be fairly easy to modify to suit your own needs, that solves the dilemma of running a command across multiple systems and having to wait for each one to finish before moving onto the next. This is particularly problematic when running WMI commands which takes 2-10 seconds per device to return results. This script, in theory could be used to run the command on all servers at the same time – quite the time saver.

The example below takes a network address (eg: 10.50.18.0) and pings all devices from .1 through to .254 (with each being pinged in its own parallel thread).

You could change this to be a group of Active Directory Computers, or well, any array of objects; and run commands against all of them in parallel.

NOTE: Even though we’re incrementing through the host addresses from 1 to 254, the parallel nature of what we’re doing means that some threads will likely finish out of order, and the results you get back will be somewhat random. IE; you could get results for 10.50.18.220 before 10.50.18.219 is returned.

And I’ve also included a progress bar, because, why not.

# Gather network address (must end in .0)
$network = read-host "Enter network address";
$networkcheck = $network.substring($network.length-2);

if ($networkcheck -eq ".0") {
    # Drop the .0 from the network address
    $network = $network.substring(0,$network.length-1);

    # Create Runspace Pool with 500 threads
    $pool = [RunspaceFactory]::CreateRunspacePool(1, 500)
    $pool.ApartmentState = "MTA"
    $pool.open()
    $runspaces = @()
     
    # The script you want run against each host
    $scriptblock = {

        # Take the IP address as a parameter
        param ([string]$ip);
        
        # Ping IP address    
        $online = test-connection $ip -count 1 -ea 0;

        # Print IP address if online
    	if ($online) {
    		$ip;
    	}
    }
     
    # Loop through numbers 1 to 254 
    foreach ($hostnumber in 1..254) {

    	# Set full IP address
    	$ip = $network + $hostnumber;

        $runspace = [powershell]::create()

        # Add script block to runspace (use $null to avoid noise)
        $null = $runspace.addscript($scriptblock)

        # Add IP address as an argument to the scriptblock (use $null to avoid noise)
        $null = $runspace.addargument($ip)

        # Add/create new runspace
        $runspace.runspacepool = $pool
        $runspaces += [pscustomobject]@{pipe=$runspace; Status=$runspace.begininvoke() }
    }
     
    # Prepare the progress bar
    $currentcount = 0;
    $totalcount = ($runspaces | measure-object).count;

    # Pause until all runspaces have completed
    while ($runspaces.status -ne $null)
    {
        $completed = $runspaces | where { $_.status.iscompleted -eq $true };
        
        # Update progress bar
        $currentcount = $currentcount + ($completed | measure-object).count;
        write-progress -activity "Pinging IP Addresses..." -percentcomplete (([int]$currentcount/[int]$totalcount)*100);
        
        # Clear completed runspaces
        foreach ($runspace in $completed)
        {
            $runspace.pipe.endinvoke($runspace.status)
            $runspace.status = $null            
        }
    }

    # Clean-up Runspace Pool
    $pool.close();
    $pool.dispose();

} else {
    write-host "NOT A VALID NETWORK ADDRESS" -foregroundcolor "red" -backgroundcolor "black";
}

# Gather network address (must end in .0)

$network = read-host "Enter network address";

$networkcheck = $network.substring($network.length-2);

if ($networkcheck -eq ".0") {

# Drop the .0 from the network address

$network = $network.substring(0,$network.length-1);

# Create Runspace Pool with 500 threads

$pool = [RunspaceFactory]::CreateRunspacePool(1, 500)

$pool.ApartmentState = "MTA"

$pool.open()

$runspaces = @()

# The script you want run against each host

$scriptblock = {

# Take the IP address as a parameter

param ([string]$ip);

# Ping IP address

$online = test-connection $ip -count 1 -ea 0;

# Print IP address if online

if ($online) {

$ip;

}

# Loop through numbers 1 to 254

foreach ($hostnumber in 1..254) {

# Set full IP address

$ip = $network + $hostnumber;

$runspace = [powershell]::create()

# Add script block to runspace (use $null to avoid noise)

$null = $runspace.addscript($scriptblock)

# Add IP address as an argument to the scriptblock (use $null to avoid noise)

$null = $runspace.addargument($ip)

# Add/create new runspace

$runspace.runspacepool = $pool

$runspaces += [pscustomobject]@{pipe=$runspace; Status=$runspace.begininvoke() }

}

# Prepare the progress bar

$currentcount = 0;

$totalcount = ($runspaces | measure-object).count;

# Pause until all runspaces have completed

while ($runspaces.status -ne $null)

{

$completed = $runspaces | where { $_.status.iscompleted -eq $true };

# Update progress bar

$currentcount = $currentcount + ($completed | measure-object).count;

write-progress -activity "Pinging IP Addresses..." -percentcomplete (([int]$currentcount/[int]$totalcount)*100);

# Clear completed runspaces

foreach ($runspace in $completed)

{

$runspace.pipe.endinvoke($runspace.status)

$runspace.status = $null

}

# Clean-up Runspace Pool

$pool.close();

$pool.dispose();

} else {

write-host "NOT A VALID NETWORK ADDRESS" -foregroundcolor "red" -backgroundcolor "black";

}

The result will be a list of IP addresses that were successfully pinged, displayed to the screen:

HKEY_LOCAL_MACHINE

Every problem is an opportunity.

Beginning parallel processing in PowerShell

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