Merge pull request #422 from Particular/Issue-416

@indualagarsamy based on your testing feedback I'm merging :) Thanks for your help

Author: Greg Bielleman

src/ServiceControl/CustomChecks/CustomCheckNotifications.cs

@@ -0,0 +1,85 @@
+namespace ServiceControl.CustomChecks
+{
+    using System;
+    using System.Linq;
+    using System.Reactive.Concurrency;
+    using System.Reactive.Linq;
+    using NServiceBus;
+    using NServiceBus.Logging;
+    using Raven.Abstractions.Data;
+    using Raven.Client;
+    using INeedInitialization = NServiceBus.INeedInitialization;
+
+    public class CustomCheckNotifications : INeedInitialization, IWantToRunWhenBusStartsAndStops, IObserver<IndexChangeNotification>
+    {
+        IDocumentStore store;
+        IBus bus;
+        int lastCount;
+        IDisposable subscription;
+        ILog logging = LogManager.GetLogger(typeof(CustomCheckNotifications));
+    
+        public CustomCheckNotifications()
+        {
+            // Need this because INeedInitialization does not use DI instead use Activator.CreateInstance
+        }
+
+        public CustomCheckNotifications(IDocumentStore store, IBus bus)
+        {
+            this.bus = bus;
+            this.store = store;
+        }
+
+        public void Init()
+        {
+            Configure.Component<CustomCheckNotifications>(DependencyLifecycle.SingleInstance);
+        }
+
+        public void OnNext(IndexChangeNotification value)
+        {
+           UpdateCount();
+        }
+
+        void UpdateCount()
+        {
+            try
+            {
+                using (var session = store.OpenSession())
+                {
+                    var failedCustomCheckCount = session.Query<CustomCheck, CustomChecksIndex>().Count(p => p.Status == Status.Fail);
+                    if (lastCount == failedCustomCheckCount)
+                        return;
+                    lastCount = failedCustomCheckCount;
+                    bus.Publish(new CustomChecksUpdated
+                    {
+                        Failed = lastCount
+                    });
+                }
+            }
+            catch (Exception ex)
+            {
+                logging.WarnFormat("Failed to emit CustomCheckUpdated - {0}", ex);
+            }
+
+        }
+
+        public void OnError(Exception error)
+        {
+            //Ignore
+        }
+
+        public void OnCompleted()
+        {
+            //Ignore
+        }
+
+        public void Start()
+        {
+            subscription = store.Changes().ForIndex("CustomChecksIndex").SubscribeOn(Scheduler.Default).Subscribe(this);
+        }
+
+        public void Stop()
+        {
+            subscription.Dispose();
+        }
+    }
+}

src/ServiceControl/CustomChecks/CustomChecksComputation.cs

@@ -0,0 +1,86 @@
+namespace ServiceControl.MessageFailures
+{
+    using System;
+    using System.Linq;
+    using System.Reactive.Concurrency;
+    using System.Reactive.Linq;
+    using NServiceBus;
+    using NServiceBus.Logging;
+    using Raven.Abstractions.Data;
+    using Raven.Client;
+    using ServiceControl.Contracts.MessageFailures;
+    using ServiceControl.MessageFailures.Api;
+    using INeedInitialization = NServiceBus.INeedInitialization;
+
+    public class FailedMessageViewIndexNotifications : INeedInitialization, IWantToRunWhenBusStartsAndStops, IObserver<IndexChangeNotification>
+    {
+        IBus bus;
+        IDocumentStore store;
+        int lastCount;
+        IDisposable subscription;
+        ILog logging = LogManager.GetLogger(typeof(FailedMessageViewIndexNotifications));
+        
+        public FailedMessageViewIndexNotifications()
+        {
+            // Need this because INeedInitialization does not use DI instead use Activator.CreateInstance
+        }
+
+        public FailedMessageViewIndexNotifications(IDocumentStore store, IBus bus)
+        {
+            this.bus = bus;
+            this.store = store;
+        }
+
+        public void OnNext(IndexChangeNotification value)
+        {
+            UpdatedCount();
+        }
+
+        public void OnError(Exception error)
+        {
+            //Ignore  
+        }
+
+        public void OnCompleted()
+        {
+            //Ignore
+        }
+
+        void UpdatedCount()
+        {
+            try
+            {
+                using (var session = store.OpenSession())
+                {
+                    var failedMessageCount = session.Query<FailedMessage, FailedMessageViewIndex>().Count(p => p.Status == FailedMessageStatus.Unresolved);
+                    if (lastCount == failedMessageCount)
+                        return;
+                    lastCount = failedMessageCount;
+                    bus.Publish(new MessageFailuresUpdated
+                    {
+                        Total = failedMessageCount
+                    });
+                }
+            }
+            catch(Exception ex)
+            {
+                logging.WarnFormat("Failed to emit MessageFailuresUpdated - {0}", ex);
+            }
+        }
+
+        public void Init()
+        {
+            Configure.Component<FailedMessageViewIndexNotifications>(DependencyLifecycle.SingleInstance);
+        }
+
+        public void Start()
+        {
+            subscription = store.Changes().ForIndex("FailedMessageViewIndex").SubscribeOn(Scheduler.Default).Subscribe(this);
+        }
+
+        public void Stop()
+        {
+            subscription.Dispose();
+        }
+    }
+}