Allow to specify localized category name, counter name and instance name for CheckDeadLetterQueue custom check

src/ServiceControl.Transports.Msmq/CheckDeadLetterQueue.cs

@@ -1,6 +1,7 @@
 namespace ServiceControl.MSMQ.DLQMonitor
 {
     using System;
+    using System.Configuration;
     using System.Diagnostics;
     using System.Threading.Tasks;
     using NServiceBus.CustomChecks;
@@ -13,31 +14,100 @@ public CheckDeadLetterQueue() :
         {
             Logger.Debug("MSMQ Dead Letter Queue custom check starting");
 
-            dlqPerformanceCounter = new PerformanceCounter(
-                categoryName: "MSMQ Queue",
-                counterName: "Messages in Queue",
-                instanceName: "Computer Queues",
-                readOnly: true);
+            categoryName = Read("Msmq/PerformanceCounterCategoryName", "MSMQ Queue");
+            counterName = Read("Msmq/PerformanceCounterName", "Messages in Queue");
+            counterInstanceName = Read("Msmq/PerformanceCounterInstanceName", "Computer Queues");
+
+            try
+            {
+                dlqPerformanceCounter = new PerformanceCounter(categoryName, counterName, counterInstanceName, readOnly: true);
+            }
+            catch (InvalidOperationException ex)
+            {
+                Logger.Error(CounterMightBeLocalized(categoryName, counterName, counterInstanceName), ex);
+            }
         }
 
         public override Task<CheckResult> PerformCheck()
         {
             Logger.Debug("Checking Dead Letter Queue length");
-            var currentValue = dlqPerformanceCounter.NextValue();
+            float currentValue;
+            string result;
+            try
+            {
+                if (dlqPerformanceCounter == null)
+                {
+                    throw new InvalidOperationException("Unable to create performance counter instance.");
+                }
+
+                currentValue = dlqPerformanceCounter.NextValue();
+            }
+            catch (InvalidOperationException ex)
+            {
+                result = CounterMightBeLocalized(categoryName, counterName, counterInstanceName);
+                Logger.Warn(result, ex);
+                return CheckResult.Failed(result);
+            }
 
             if (currentValue <= 0)
             {
                 Logger.Debug("No messages in Dead Letter Queue");
                 return CheckResult.Pass;
             }
 
-            var result = $"{currentValue} messages in the Dead Letter Queue on {Environment.MachineName}. This could indicate a problem with ServiceControl's retries. Please submit a support ticket to Particular using support@particular.net if you would like help from our engineers to ensure no message loss while resolving these dead letter messages.";
-
+            result = MessagesInDeadLetterQueue(currentValue);
             Logger.Warn(result);
             return CheckResult.Failed(result);
         }
 
+        static string MessagesInDeadLetterQueue(float currentValue)
+        {
+            return $"{currentValue} messages in the Dead Letter Queue on {Environment.MachineName}. This could indicate a problem with ServiceControl's retries. Please submit a support ticket to Particular using support@particular.net if you would like help from our engineers to ensure no message loss while resolving these dead letter messages.";
+        }
+
+        static string CounterMightBeLocalized(string categoryName, string counterName, string counterInstanceName)
+        {
+            return
+                $"Unable to read the Dead Letter Queue length. The performance counter with category '{categoryName}' and name '{counterName}' and instance name '{counterInstanceName}' is not available. "
+                + "It is possible that the counter category, name and instance name have been localized into different languages. "
+                + @"Consider overriding the counter category, name and instance name in the application configuration file by adding:
+   <appSettings>
+     <add key=""ServiceControl/Msmq/PerformanceCounterCategoryName"" value=""LocalizedCategoryName"" />
+     <add key=""ServiceControl/Msmq/PerformanceCounterName"" value=""LocalizedCounterName"" />
+     <add key=""ServiceControl/Msmq/PerformanceCounterInstanceName"" value=""LocalizedCounterInstanceName"" />
+   </appSettings>
+";
+        }
+
+        // from ConfigFileSettingsReader since we cannot reference ServiceControl 
+        static string Read(string name, string defaultValue = default)
+        {
+            return Read("ServiceControl", name, defaultValue);
+        }
+
+        static string Read(string root, string name, string defaultValue = default)
+        {
+            return TryRead(root, name, out var value) ? value : defaultValue;
+        }
+
+        static bool TryRead(string root, string name, out string value)
+        {
+            var fullKey = $"{root}/{name}";
+
+            if (ConfigurationManager.AppSettings[fullKey] != null)
+            {
+                value = ConfigurationManager.AppSettings[fullKey];
+                return true;
+            }
+
+            value = default;
+            return false;
+        }
+
         PerformanceCounter dlqPerformanceCounter;
+        private string categoryName;
+        private string counterName;
+        private string counterInstanceName;
 
         static readonly ILog Logger = LogManager.GetLogger(typeof(CheckDeadLetterQueue));
     }