Merge pull request #22 from Icinga/fix/Bug-MSSQL-Buffer-Cache-Hit-Ratio-returns-wrong-metric

Fix: MSSQL Resource check returns wrong metrics

MSSQL Buffer Cache Hit Ratio and Average Latch Wait Time returns the wrong value for Buffer Cache Hit Ratio. We should calculate the proper value to return the correct value.

Author: LordHepipud

plugins/Invoke-IcingaCheckMSSQLResource.psm1

@@ -74,21 +74,21 @@
 function Invoke-IcingaCheckMSSQLResource()
 {
     param (
-        $PageLifeExpectancyCritical       = $null,
-        $PageLifeExpectancyWarning        = $null,
-        $AverageLatchWaitTimeCritical     = $null,
-        $AverageLatchWaitTimeWarning      = $null,
-        $BufferCacheHitRatioCritical      = $null,
-        $BufferCacheHitRatioWarning       = $null,
+        $PageLifeExpectancyCritical   = $null,
+        $PageLifeExpectancyWarning    = $null,
+        $AverageLatchWaitTimeCritical = $null,
+        $AverageLatchWaitTimeWarning  = $null,
+        $BufferCacheHitRatioCritical  = $null,
+        $BufferCacheHitRatioWarning   = $null,
         [string]$SqlUsername,
         [securestring]$SqlPassword,
-        [string]$SqlHost                  = "localhost",
-        [int]$SqlPort                     = 1433,
+        [string]$SqlHost              = "localhost",
+        [int]$SqlPort                 = 1433,
         [string]$SqlDatabase,
-        [switch]$IntegratedSecurity       = $FALSE,
+        [switch]$IntegratedSecurity   = $FALSE,
         [switch]$NoPerfData,
         [ValidateSet(0, 1, 2)]
-        [int]$Verbosity                   = 0
+        [int]$Verbosity               = 0
     );
 
     [hashtable]$CheckPackages = @{};
@@ -100,9 +100,27 @@ function Invoke-IcingaCheckMSSQLResource()
         -PerformanceCounters @(
             '\SQLServer:Buffer Manager\page life expectancy',
             '\SQLServer:Buffer Manager\Buffer cache hit ratio',
-            '\SQLServer:Latches\Average Latch Wait Time (ms)'
+            '\SQLServer:Latches\Average Latch Wait Time (ms)',
+            '\SQLServer:Buffer Manager\Buffer cache hit ratio base',
+            '\SQLServer:Latches\Average Latch Wait Time Base'
         );
 
+    [decimal]$BufferRatioBase   = 1;
+    [decimal]$LatchWaitTimeBase = 1;
+
+    foreach ($entry in $PerfCounters) {
+        switch ($entry.counter_name) {
+            'Buffer cache hit ratio base' {
+                $BufferRatioBase = $entry.cntr_value;
+                break;
+            };
+            'Average Latch Wait Time Base' {
+                $LatchWaitTimeBase = $entry.cntr_value;
+                break;
+            };
+        }
+    }
+
     $InstanceName = Get-IcingaMSSQLInstanceName -SqlConnection $SqlConnection;
 
     # Close the connection as we no longer require it
@@ -116,27 +134,32 @@ function Invoke-IcingaCheckMSSQLResource()
     foreach ($Entry in $PerfCounters) {
         $FullName = Get-IcingaMSSQLPerfCounterPathFromDBObject -DBObject $Entry;
 
-        Add-IcingaHashtableItem `
-            -Hashtable $CheckPackages `
-            -Key ($Entry.object_name) `
-            -Value (New-IcingaCheckPackage -Name $Entry.object_name -OperatorAnd -Verbose $Verbosity) | Out-Null;
-
         <# https://docs.microsoft.com/en-us/sql/relational-databases/performance-monitor/sql-server-buffer-manager-object?view=sql-server-ver15 #>
         switch ($FullName) {
             '\SQLServer:Buffer Manager\page life expectancy' {
                 $Check = (New-IcingaCheck -Name $Entry.counter_name -Value $Entry.cntr_value).WarnOutOfRange($PageLifeExpectancyWarning).CritOutOfRange($PageLifeExpectancyCritical);
                 break;
             };
             '\SQLServer:Buffer Manager\Buffer cache hit ratio' {
-                $Check = (New-IcingaCheck -Name $Entry.counter_name -Value $Entry.cntr_value).WarnOutOfRange($BufferCacheHitRatioWarning).CritOutOfRange($BufferCacheHitRatioCritical);
+                $Check = (New-IcingaCheck -Name $Entry.counter_name -Value (($Entry.cntr_value * 1.0 / $BufferRatioBase) * 100) -Unit '%').WarnOutOfRange($BufferCacheHitRatioWarning).CritOutOfRange($BufferCacheHitRatioCritical);
                 break;
             };
             '\SQLServer:Latches\Average Latch Wait Time (ms)' {
-                $Check = (New-IcingaCheck -Name $Entry.counter_name -Value $Entry.cntr_value).WarnOutOfRange($AverageLatchWaitTimeWarning).CritOutOfRange($AverageLatchWaitTimeCritical);
+                $Check = (New-IcingaCheck -Name $Entry.counter_name -Value ($Entry.cntr_value / $LatchWaitTimeBase) -Unit 'ms').WarnOutOfRange($AverageLatchWaitTimeWarning).CritOutOfRange($AverageLatchWaitTimeCritical);
                 break;
-            }
+            };
+        }
+
+        # Do not add these metrics to our check package of create checks for them
+        if ($FullName -eq '\SQLServer:Buffer Manager\Buffer cache hit ratio base' -Or $FullName -eq '\SQLServer:Latches\Average Latch Wait Time Base') {
+            continue;
         }
 
+        Add-IcingaHashtableItem `
+            -Hashtable $CheckPackages `
+            -Key ($Entry.object_name) `
+            -Value (New-IcingaCheckPackage -Name $Entry.object_name -OperatorAnd -Verbose $Verbosity) | Out-Null;
+
         if ($null -ne $Check) {
             # The check package for our counter category
             (Get-IcingaHashtableItem -Hashtable $CheckPackages -Key ($Entry.object_name)).AddCheck($Check) | Out-Null;