icinga-powershell-framework/lib/core/perfcounter/New-IcingaPerformanceCounterArray.psm1

<#
  # This function will make monitoring an entire list of
  # Performance counters even more easier. We simply provide
  # an array of Performance Counters  to this module
  # and we will receive a construct-save result of an
  # hashtable with all performance counters including
  # the corresponding values. In that case the code
  # size decreases for larger modules.
  # Example:
    $counter = New-IcingaPerformanceCounterArray @(
        '\Memory\Available Bytes',
        '\Memory\% Committed Bytes In Use'
    );
  #>
function New-IcingaPerformanceCounterArray()
{
    param(
        [array]$CounterArray = @()
    )

    [hashtable]$CounterResult = @{};
    [bool]$RequireSleep       = $TRUE;
    foreach ($counter in $CounterArray) {
        # We want to speed up things with loading, so we will check if a specified
        # Counter is already cached within our hashtable. If it is not, we sleep
        # at the end of the function the required 500ms and don't have to wait
        # NumOfCounters * 500 milliseconds for the first runs. This will speed
        # up the general loading of counters and will not require some fancy
        # pre-caching / configuration handler
        # TODO: Re-Implement caching for counters
        #if ($Icinga2.Cache.PerformanceCounter -ne $null) {
        #    if ($Icinga2.Cache.PerformanceCounter.ContainsKey($counter) -eq $TRUE) {
        $RequireSleep = $FALSE;
        #    }
        #}
        $obj = New-IcingaPerformanceCounter -Counter $counter -SkipWait $TRUE;
        if ($CounterResult.ContainsKey($obj.Name()) -eq $FALSE) {
            $CounterResult.Add($obj.Name(), $obj.Value());
        }
    }

    # TODO: Add a cache for our Performance Counters to only fetch them once
    #       for each session to speed up the loading. This cold be something like
    #       this:
    # New-IcingaPerformanceCounterCache $CounterResult;
    # Internally we could do something like this
    # $global:Icinga_PerfCounterCache += $CounterResult;

    # Above we initialse ever single counter and we only require a sleep once
    # in case a new, yet unknown counter was added
    if ($RequireSleep) {
        Start-Sleep -Milliseconds 500;

        # Agreed, this is some sort of code duplication but it wouldn't make
        # any sense to create a own function for this. Why are we doing
        # this anway?
        # Simple: In case we found counters which have yet not been initialised
        #         we did this above. Now we have waited 500 ms to receive proper
        #         values from these counters. As the previous generated result
        #         might have contained counters with 0 results, we will now
        #         check all counters again to receive the proper values.
        #         Agreed, might sound like a overhead, but the impact only
        #         applies to the first call of the module with the counters.
        #         This 'duplication' however decreased the execution from
        #         certain modules from 25s to 1s on the first run. Every
        #         additional run is then beeing executed within 0.x s
        #         which sounds like a very good performance and solution
        $CounterResult = @{};
        foreach ($counter in $CounterArray) {
            $obj = New-IcingaPerformanceCounter -Counter $counter -SkipWait $TRUE;
            if ($CounterResult.ContainsKey($obj.Name()) -eq $FALSE) {
                $CounterResult.Add($obj.Name(), $obj.Value());
            }
        }
    }

    return $CounterResult;
}