Powershell Teams message wrapper sending manually but not automatically

Question

I have a script that's designed to ping another host across a site-to-site VPN tunnel every minute. After 10 minutes, it checks the average uptime of test-connection, and if it falls below a certain threshold, it sends a Teams message telling us to check things out.

This works perfectly well when I manually run the script in situ, however, when I leave it to run as a background job, it isn't sending the Teams messages.

My question is this: as a relatively new sysadmin, the tools in my toolkit are pretty limited. Does anyone have a good tip for where I should start looking, to troubleshoot this issue? To rule out potential problems with my script, I've also included it below. But I suspect the issue is more to do with leaving the script to run on a server that I then log out of. The server in question is running Windows Server 2012 (yes I know, migration is on my to-do list).

Import-Module message_module # a module i wrote to wrap messages to Teams webhooks (included below)

# this array will accept output values from the ongoing test
$test_table = new-object system.collections.arraylist
# this index counts how many times we've checked recently
[int32[]]$test_index = 1
# our desired threshold for uptime / response
$uptime = .8
# how many minutes to count before testing
$count_length = 10
# IP to ping
$ping_ip = 'XXX.XXX.XXX.XXX'
$test_ip = '142.251.33.110' # google.com, used for testing

# here's the actual function that does the pinging and puts values in the arraylist
function Ping-VPN {
    $ping_host = test-connection $ping_ip -erroraction silentlycontinue
    if ( $ping_host ) {
        $test_table.add(1) > $null
    } else {
        $test_table.add(0) > $null
    }
}

# this function calculates the average of the values in test_table, and then clears them
function Get-Average-Uptime {
    $sum = 0
    foreach ($entry in $test_table) {
        $sum += $entry
    }
    $avg = $sum / $test_table.count
    return $avg
}

function Main-Loop {
    while ( $test_index -lt $count_length ) {
        Ping-VPN
        $test_index += 1
        start-sleep -seconds 60
    }
    $avguptime = Get-Average-Uptime
    $test_table.clear
    if ( $avguptime -lt $uptime ) {
        $title = "XXX/XXX VPN Down"
        $message = "XXXXXX response to ping from XXXXXXX at less than desired rate.  Please investigate."
        Send-TeamsMessage -Message $message -Title $title
        start-sleep -seconds 3600 # sleep for an hour, to avoid spamming us
    }
    $test_index = 0 # restart the testing interval
    Main-Loop
}

Main-Loop

And the module code:

function Send-TeamsMessage {

    Param( 
        [Parameter(Position = 0, Mandatory = $true)][String]$Message, 
        [Parameter(Position = 1, Mandatory = $true)][String]$Title
    ) 

    $JSONBody = [PSCustomObject][Ordered]@{
        "@type"      = "MessageCard"
        "@context"   = "http://schema.org/extensions"
        "themeColor" = '0078D7'
        "title"      = $Title
        "text"       = $Message
    }
    
    $TeamMessageBody = ConvertTo-Json $JSONBody -Depth 100
    
    $parameters = @{
        "URI"         = 'XXXXXXXX (webhook URI)'
        "Method"      = 'POST'
        "Body"        = $TeamMessageBody
        "ContentType" = 'application/json'
    }
    
    Invoke-RestMethod @parameters | Out-Null
}

Export-ModuleMember -Function Send-TeamsMessage

Right now, I'm calling the main file with:

start-job -file C:\path\to\file.ps1

Then minimizing the terminal and disconnecting from the server. I suspect the problem is something to do with this, that I'm missing something really obvious.

Answer 1

As it turns out, this question is quite similar to another, though they're phrased very differently.

Basically, what I need to do is to run the script as NT AUTHORITY\System on startup. Run an infinite command on Windows Server even if someone is logged out