Use EventAggregator to decouple several classes

BTCPayServer.Tests/ServerTester.cs

@@ -230,7 +230,7 @@ namespace BTCPayServer.Tests
                 var match = new TransactionMatch();
                 match.Outputs.Add(new KeyPathInformation() { ScriptPubKey = address.ScriptPubKey });
                 var content = new StringContent(new NBXplorer.Serializer(Network).ToString(match), new UTF8Encoding(false), "application/json");
-                var uri = controller.GetCallbackUriAsync(req).GetAwaiter().GetResult();
+                var uri = controller.GetCallbackUriAsync().GetAwaiter().GetResult();
 
                 HttpRequestMessage message = new HttpRequestMessage();
                 message.Method = HttpMethod.Post;
@@ -242,7 +242,7 @@ namespace BTCPayServer.Tests
             else
             {
 
-                var uri = controller.GetCallbackBlockUriAsync(req).GetAwaiter().GetResult();
+                var uri = controller.GetCallbackBlockUriAsync().GetAwaiter().GetResult();
                 HttpRequestMessage message = new HttpRequestMessage();
                 message.Method = HttpMethod.Post;
                 message.RequestUri = uri;

BTCPayServer/CompositeDisposable.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace BTCPayServer
+{
+    public class CompositeDisposable : IDisposable
+    {
+        List<IDisposable> _Disposables = new List<IDisposable>();
+        public void Add(IDisposable disposable) { _Disposables.Add(disposable); }
+        public void Dispose()
+        {
+            foreach (var d in _Disposables)
+                d.Dispose();
+            _Disposables.Clear();
+        }
+    }
+}

BTCPayServer/Controllers/CallbackController.cs

@@ -16,6 +16,10 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using BTCPayServer.Configuration;
+using BTCPayServer.Events;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Hosting.Server.Features;
+using Microsoft.AspNetCore.Hosting.Server;
 
 namespace BTCPayServer.Controllers
 {
@@ -30,21 +34,23 @@ namespace BTCPayServer.Controllers
         }
         SettingsRepository _Settings;
         Network _Network;
-        InvoiceWatcher _Watcher;
         ExplorerClient _Explorer;
         BTCPayServerOptions _Options;
-
+        EventAggregator _EventAggregator;
+        IServer _Server;
         public CallbackController(SettingsRepository repo,
                                   ExplorerClient explorer,
-                                  InvoiceWatcherAccessor watcher,
+                                  EventAggregator eventAggregator,
                                   BTCPayServerOptions options,
+                                  IServer server,
                                   Network network)
         {
             _Settings = repo;
             _Network = network;
-            _Watcher = watcher.Instance;
             _Explorer = explorer;
             _Options = options;
+            _EventAggregator = eventAggregator;
+            _Server = server;
         }
 
         [Route("callbacks/transactions")]
@@ -52,7 +58,6 @@ namespace BTCPayServer.Controllers
         public async Task NewTransaction(string token)
         {
             await AssertToken(token);
-            Logs.PayServer.LogInformation("New transaction callback");
             //We don't want to register all the json converter at MVC level, so we parse here
             var serializer = new NBXplorer.Serializer(_Network);
             var content = await new StreamReader(Request.Body, new UTF8Encoding(false), false, 1024, true).ReadToEndAsync();
@@ -60,7 +65,10 @@ namespace BTCPayServer.Controllers
 
             foreach (var output in match.Outputs)
             {
-                await _Watcher.NotifyReceived(output.ScriptPubKey);
+                var evt = new TxOutReceivedEvent();
+                evt.ScriptPubKey = output.ScriptPubKey;
+                evt.Address = output.ScriptPubKey.GetDestinationAddress(_Network);
+                _EventAggregator.Publish(evt);
             }
         }
 
@@ -69,8 +77,7 @@ namespace BTCPayServer.Controllers
         public async Task NewBlock(string token)
         {
             await AssertToken(token);
-            Logs.PayServer.LogInformation("New block callback");
-            await _Watcher.NotifyBlock();
+            _EventAggregator.Publish(new NewBlockEvent());
         }
 
         private async Task AssertToken(string token)
@@ -80,15 +87,15 @@ namespace BTCPayServer.Controllers
                 throw new BTCPayServer.BitpayHttpException(400, "invalid-callback-token");
         }
 
-        public async Task<Uri> GetCallbackUriAsync(HttpRequest request)
+        public async Task<Uri> GetCallbackUriAsync()
         {
             string token = await GetToken();
-            return BuildCallbackUri(request, "callbacks/transactions?token=" + token);
+            return BuildCallbackUri("callbacks/transactions?token=" + token);
         }
 
-        public async Task RegisterCallbackUriAsync(DerivationStrategyBase derivationScheme, HttpRequest request)
+        public async Task RegisterCallbackUriAsync(DerivationStrategyBase derivationScheme)
         {
-            var uri = await GetCallbackUriAsync(request);
+            var uri = await GetCallbackUriAsync();
             await _Explorer.SubscribeToWalletAsync(uri, derivationScheme);
         }
 
@@ -104,19 +111,29 @@ namespace BTCPayServer.Controllers
             return token;
         }
 
-        public async Task<Uri> GetCallbackBlockUriAsync(HttpRequest request)
+        public async Task<Uri> GetCallbackBlockUriAsync()
         {
             string token = await GetToken();
-            return BuildCallbackUri(request, "callbacks/blocks?token=" + token);
+            return BuildCallbackUri("callbacks/blocks?token=" + token);
         }
 
-        private Uri BuildCallbackUri(HttpRequest request, string callbackPath)
+        private Uri BuildCallbackUri(string callbackPath)
         {
-            string baseUrl = _Options.InternalUrl == null ? request.GetAbsoluteRoot() : _Options.InternalUrl.AbsolutePath;
+            var address = _Server.Features.Get<IServerAddressesFeature>().Addresses
+                                 .Select(c => new Uri(TransformToRoutable(c)))
+                                 .First();
+            var baseUrl = _Options.InternalUrl == null ? address.AbsoluteUri : _Options.InternalUrl.AbsoluteUri;
             baseUrl = baseUrl.WithTrailingSlash();
             return new Uri(baseUrl + callbackPath);
         }
 
+        private string TransformToRoutable(string host)
+        {
+            if (host.StartsWith("http://0.0.0.0"))
+                host = host.Replace("http://0.0.0.0", "http://127.0.0.1");
+            return host;
+        }
+
         public async Task<Uri> RegisterCallbackBlockUriAsync(Uri uri)
         {
             await _Explorer.SubscribeToBlocksAsync(uri);

BTCPayServer/Controllers/StoresController.cs

@@ -198,7 +198,7 @@ namespace BTCPayServer.Controllers
                         {
                             var strategy = ParseDerivationStrategy(model.DerivationScheme, model.DerivationSchemeFormat);
                             await _Wallet.TrackAsync(strategy);
-                            await _CallbackController.RegisterCallbackUriAsync(strategy, Request);
+                            await _CallbackController.RegisterCallbackUriAsync(strategy);
                         }
                         store.DerivationStrategy = model.DerivationScheme;
                     }

BTCPayServer/EventAggregator.cs

@@ -0,0 +1,130 @@
+using System;
+using Microsoft.Extensions.Logging;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using BTCPayServer.Logging;
+
+namespace BTCPayServer
+{
+    public interface IEventAggregatorSubscription : IDisposable
+    {
+        void Unsubscribe();
+        void Resubscribe();
+    }
+    public class EventAggregator : IDisposable
+    {
+        class Subscription : IEventAggregatorSubscription
+        {
+            private EventAggregator aggregator;
+            Type t;
+            Action<object> act;
+            public Subscription(EventAggregator aggregator, Type t)
+            {
+                this.aggregator = aggregator;
+                this.t = t;
+            }
+
+            public Action<Object> Act { get; set; }
+
+            public void Dispose()
+            {
+                lock (this.aggregator._Subscriptions)
+                {
+                    if (this.aggregator._Subscriptions.TryGetValue(t, out Dictionary<Subscription, Action<object>> actions))
+                    {
+                        if (actions.Remove(this))
+                        {
+                            if (actions.Count == 0)
+                                this.aggregator._Subscriptions.Remove(t);
+                        }
+                    }
+                }
+            }
+
+            public void Resubscribe()
+            {
+                aggregator.Subscribe(t, this);
+            }
+
+            public void Unsubscribe()
+            {
+                Dispose();
+            }
+        }
+
+        public void Publish<T>(T evt) where T : class
+        {
+            if (evt == null)
+                throw new ArgumentNullException(nameof(evt));
+            List<Action<object>> actionList = new List<Action<object>>();
+            lock (_Subscriptions)
+            {
+                if (_Subscriptions.TryGetValue(typeof(T), out Dictionary<Subscription, Action<object>> actions))
+                {
+                    actionList = actions.Values.ToList();
+                }
+            }
+
+            Logs.Events.LogInformation($"New event: {evt.ToString()}");
+            foreach (var sub in actionList)
+            {
+                try
+                {
+                    sub(evt);
+                }
+                catch (Exception ex)
+                {
+                    Logs.Events.LogError(ex, $"Error while calling event handler");
+                }
+            }
+        }
+
+        public IEventAggregatorSubscription Subscribe<T>(Action<IEventAggregatorSubscription, T> subscription)
+        {
+            var eventType = typeof(T);
+            var s = new Subscription(this, eventType);
+            s.Act = (o) => subscription(s, (T)o);
+            return Subscribe(eventType, s);
+        }
+
+        private IEventAggregatorSubscription Subscribe(Type eventType, Subscription subscription)
+        {
+            lock (_Subscriptions)
+            {
+                if (!_Subscriptions.TryGetValue(eventType, out Dictionary<Subscription, Action<object>> actions))
+                {
+                    actions = new Dictionary<Subscription, Action<object>>();
+                    _Subscriptions.Add(eventType, actions);
+                }
+                actions.Add(subscription, subscription.Act);
+            }
+            return subscription;
+        }
+
+        Dictionary<Type, Dictionary<Subscription, Action<object>>> _Subscriptions = new Dictionary<Type, Dictionary<Subscription, Action<object>>>();
+
+        public IEventAggregatorSubscription Subscribe<T, TReturn>(Func<T, TReturn> subscription)
+        {
+            return Subscribe(new Action<T>((t) => subscription(t)));
+        }
+
+        public IEventAggregatorSubscription Subscribe<T, TReturn>(Func<IEventAggregatorSubscription, T, TReturn> subscription)
+        {
+            return Subscribe(new Action<IEventAggregatorSubscription, T>((sub, t) => subscription(sub, t)));
+        }
+
+        public IEventAggregatorSubscription Subscribe<T>(Action<T> subscription)
+        {
+            return Subscribe(new Action<IEventAggregatorSubscription, T>((sub, t) => subscription(t)));
+        }
+
+        public void Dispose()
+        {
+            lock (_Subscriptions)
+            {
+                _Subscriptions.Clear();
+            }
+        }
+    }
+}

BTCPayServer/Events/InvoiceDataChangedEvent.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace BTCPayServer.Events
+{
+    public class InvoiceDataChangedEvent
+    {
+        public string InvoiceId { get; set; }
+
+        public override string ToString()
+        {
+            return $"Invoice {InvoiceId} data changed";
+        }
+    }
+}

BTCPayServer/Events/InvoiceStatusChangedEvent.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace BTCPayServer.Events
+{
+    public class InvoiceStatusChangedEvent
+    {
+        public string InvoiceId { get; set; }
+        public string OldState { get; set; }
+        public string NewState { get; set; }
+
+        public override string ToString()
+        {
+            return $"Invoice {InvoiceId} changed status: {OldState} => {NewState}";
+        }
+    }
+}

BTCPayServer/Events/NBXplorerStateChangedEvent.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace BTCPayServer.Events
+{
+    public class NBXplorerStateChangedEvent
+    {
+        public NBXplorerStateChangedEvent(NBXplorerState old, NBXplorerState newState)
+        {
+            NewState = newState;
+            OldState = old;
+        }
+
+        public NBXplorerState NewState { get; set; }
+        public NBXplorerState OldState { get; set; }
+
+        public override string ToString()
+        {
+            return $"NBXplorer: {OldState} => {NewState}";
+        }
+    }
+}

BTCPayServer/Events/NewBlockEvent.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace BTCPayServer.Events
+{
+    public class NewBlockEvent
+    {
+        public override string ToString()
+        {
+            return "New block";
+        }
+    }
+}

BTCPayServer/Events/TxOutReceivedEvent.cs

@@ -0,0 +1,20 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using NBitcoin;
+
+namespace BTCPayServer.Events
+{
+    public class TxOutReceivedEvent
+    {
+        public Script ScriptPubKey { get; set; }
+        public BitcoinAddress Address { get; set; }
+
+        public override string ToString()
+        {
+            String address = Address?.ToString() ?? ScriptPubKey.ToHex();
+            return $"{address} received a transaction";
+        }
+    }
+}

BTCPayServer/Hosting/BTCPayServerServices.cs

@@ -106,6 +106,7 @@ namespace BTCPayServer.Hosting
             });
             services.AddSingleton<BTCPayServerEnvironment>();
             services.TryAddSingleton<TokenRepository>();
+            services.TryAddSingleton<EventAggregator>();
             services.TryAddSingleton<Network>(o => o.GetRequiredService<BTCPayServerOptions>().Network);
             services.TryAddSingleton<ApplicationDbContextFactory>(o => 
             {
@@ -158,11 +159,11 @@ namespace BTCPayServer.Hosting
                 return new CachedRateProvider(new FallbackRateProvider(new IRateProvider[] { coinaverage, bitpay }), o.GetRequiredService<IMemoryCache>()) { CacheSpan = TimeSpan.FromMinutes(1.0) };
             });
             
-            services.TryAddSingleton<InvoiceNotificationManager>();
+            services.AddSingleton<IHostedService, InvoiceNotificationManager>();
 
             services.TryAddSingleton<InvoiceWatcherAccessor>();
             services.AddSingleton<IHostedService, InvoiceWatcher>();
-            
+            services.TryAddSingleton<Initializer>();
             services.TryAddScoped<IHttpContextAccessor, HttpContextAccessor>();
             services.TryAddSingleton<IAuthorizationHandler, OwnStoreHandler>();
             services.AddTransient<AccessTokenController>();
@@ -197,6 +198,11 @@ namespace BTCPayServer.Hosting
                     scope.ServiceProvider.GetRequiredService<ApplicationDbContext>().Database.Migrate();
                 });
             }
+
+
+
+            var initialize = app.ApplicationServices.GetService<Initializer>();
+            initialize.Init();
             app.UseMiddleware<BTCPayMiddleware>();
             return app;
         }

BTCPayServer/Hosting/BTCpayMiddleware.cs

@@ -31,19 +31,15 @@ namespace BTCPayServer.Hosting
         RequestDelegate _Next;
         CallbackController _CallbackController;
         BTCPayServerOptions _Options;
-        private NBXplorerWaiterAccessor _NbxplorerAwaiter;
 
         public BTCPayMiddleware(RequestDelegate next,
             TokenRepository tokenRepo,
             BTCPayServerOptions options,
-            NBXplorerWaiterAccessor nbxplorerAwaiter,
             CallbackController callbackController)
         {
             _TokenRepository = tokenRepo ?? throw new ArgumentNullException(nameof(tokenRepo));
             _Next = next ?? throw new ArgumentNullException(nameof(next));
-            _CallbackController = callbackController;
             _Options = options ?? throw new ArgumentNullException(nameof(options));
-            _NbxplorerAwaiter = (nbxplorerAwaiter ?? throw new ArgumentNullException(nameof(nbxplorerAwaiter)));
         }
 
 
@@ -52,7 +48,6 @@ namespace BTCPayServer.Hosting
         public async Task Invoke(HttpContext httpContext)
         {
             RewriteHostIfNeeded(httpContext);
-            await EnsureBlockCallbackRegistered(httpContext);
 
             httpContext.Request.Headers.TryGetValue("x-signature", out StringValues values);
             var sig = values.FirstOrDefault();
@@ -154,28 +149,6 @@ namespace BTCPayServer.Hosting
             }
         }
 
-        private async Task EnsureBlockCallbackRegistered(HttpContext httpContext)
-        {
-            if (!_Registered)
-            {
-                var callback = await _CallbackController.GetCallbackBlockUriAsync(httpContext.Request);
-                var unused = _NbxplorerAwaiter.Instance.WhenReady(async c =>
-                {
-                    try
-                    {
-                        await _CallbackController.RegisterCallbackBlockUriAsync(callback);
-                        Logs.PayServer.LogInformation($"Registering block callback to " + callback);
-                    }
-                    catch (Exception ex)
-                    {
-                        Logs.PayServer.LogError(ex, "Could not register block callback");
-                    }
-                    return true;
-                });
-                _Registered = true;
-            }
-        }
-
         private static async Task HandleBitpayHttpException(HttpContext httpContext, BitpayHttpException ex)
         {
             httpContext.Response.StatusCode = ex.StatusCode;

BTCPayServer/Initializer.cs

@@ -0,0 +1,45 @@
+using System;
+using Microsoft.Extensions.Logging;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using BTCPayServer.Controllers;
+using BTCPayServer.Logging;
+using BTCPayServer.Events;
+
+namespace BTCPayServer
+{
+    public class Initializer
+    {
+        EventAggregator _Aggregator;
+        CallbackController _CallbackController;
+        public Initializer(EventAggregator aggregator, 
+            CallbackController callbackController
+            )
+        {
+            _Aggregator = aggregator;
+            _CallbackController = callbackController;
+        }
+        public void Init()
+        {
+            _Aggregator.Subscribe<NBXplorerStateChangedEvent>(async (s, evt) =>
+            {
+                if (evt.NewState == NBXplorerState.Ready)
+                {
+                    s.Unsubscribe();
+                    try
+                    {
+                        var callback = await _CallbackController.GetCallbackBlockUriAsync();
+                        await _CallbackController.RegisterCallbackBlockUriAsync(callback);
+                        Logs.PayServer.LogInformation($"Registering block callback to " + callback);
+                    }
+                    catch (Exception ex)
+                    {
+                        Logs.PayServer.LogError(ex, "Could not register block callback");
+                        s.Resubscribe();
+                    }
+                }
+            });
+        }
+    }
+}

BTCPayServer/Logging/Logs.cs

@@ -17,6 +17,7 @@ namespace BTCPayServer.Logging
         {
             Configuration = factory.CreateLogger("Configuration");
             PayServer = factory.CreateLogger("PayServer");
+            Events = factory.CreateLogger("PayServer");
         }
         public static ILogger Configuration
         {
@@ -26,6 +27,12 @@ namespace BTCPayServer.Logging
         {
             get; set;
         }
+
+        public static ILogger Events
+        {
+            get; set;
+        }
+
         public const int ColumnLength = 16;
     }
 

BTCPayServer/NBXplorerWaiter.cs

@@ -9,6 +9,7 @@ using Microsoft.Extensions.Hosting;
 using NBXplorer;
 using NBXplorer.Models;
 using System.Collections.Concurrent;
+using BTCPayServer.Events;
 
 namespace BTCPayServer
 {
@@ -22,14 +23,17 @@ namespace BTCPayServer
         Synching,
         Ready
     }
+
     public class NBXplorerWaiter : IHostedService
     {
-        public NBXplorerWaiter(ExplorerClient client, NBXplorerWaiterAccessor accessor)
+        public NBXplorerWaiter(ExplorerClient client, EventAggregator aggregator, NBXplorerWaiterAccessor accessor)
         {
             _Client = client;
+            _Aggregator = aggregator;
             accessor.Instance = this;
         }
 
+        EventAggregator _Aggregator;
         ExplorerClient _Client;
         Timer _Timer;
         ManualResetEventSlim _Idle = new ManualResetEventSlim(true);
@@ -64,15 +68,6 @@ namespace BTCPayServer
             {
 
             }
-            List<Task> tasks = new List<Task>();
-            if (State == NBXplorerState.Ready)
-            {
-                while (_WhenReady.TryDequeue(out Func<ExplorerClient, Task> act))
-                {
-                    tasks.Add(act(_Client));
-                }
-            }
-            await Task.WhenAll(tasks);
         }
 
         private async Task<bool> StepAsync()
@@ -123,7 +118,6 @@ namespace BTCPayServer
             LastStatus = status;
             if (oldState != State)
             {
-                Logs.PayServer.LogInformation($"NBXplorerWaiter status changed: {oldState} => {State}");
                 if (State == NBXplorerState.Synching)
                 {
                     SetInterval(TimeSpan.FromSeconds(10));
@@ -132,6 +126,7 @@ namespace BTCPayServer
                 {
                     SetInterval(TimeSpan.FromMinutes(1));
                 }
+                _Aggregator.Publish(new NBXplorerStateChangedEvent(oldState, State));
             }
             return oldState != State;
         }
@@ -145,28 +140,6 @@ namespace BTCPayServer
             catch { }
         }
 
-        public Task<T> WhenReady<T>(Func<ExplorerClient, Task<T>> act)
-        {
-            if (State == NBXplorerState.Ready)
-                return act(_Client);
-            TaskCompletionSource<T> completion = new TaskCompletionSource<T>();
-            _WhenReady.Enqueue(async client =>
-            {
-                try
-                {
-                    var result = await act(client);
-                    completion.SetResult(result);
-                }
-                catch (Exception ex)
-                {
-                    completion.SetException(ex);
-                }
-            });
-            return completion.Task;
-        }
-
-        ConcurrentQueue<Func<ExplorerClient, Task>> _WhenReady = new ConcurrentQueue<Func<ExplorerClient, Task>>();
-
         private async Task<StatusResult> GetStatusWithTimeout()
         {
             CancellationTokenSource cts = new CancellationTokenSource();

BTCPayServer/Services/Invoices/InvoiceNotificationManager.cs

@@ -15,10 +15,12 @@ using NBitpayClient;
 using Newtonsoft.Json.Linq;
 using Newtonsoft.Json;
 using System.Collections.Concurrent;
+using Microsoft.Extensions.Hosting;
+using BTCPayServer.Events;
 
 namespace BTCPayServer.Services.Invoices
 {
-    public class InvoiceNotificationManager
+    public class InvoiceNotificationManager : IHostedService
     {
         public static HttpClient _Client = new HttpClient();
 
@@ -41,16 +43,32 @@ namespace BTCPayServer.Services.Invoices
         }
 
         IBackgroundJobClient _JobClient;
+        EventAggregator _EventAggregator;
+        InvoiceRepository _InvoiceRepository;
+
         public InvoiceNotificationManager(
             IBackgroundJobClient jobClient,
+            EventAggregator eventAggregator,
+            InvoiceRepository invoiceRepository,
             ILogger<InvoiceNotificationManager> logger)
         {
             Logger = logger as ILogger ?? NullLogger.Instance;
             _JobClient = jobClient;
+            _EventAggregator = eventAggregator;
+            _InvoiceRepository = invoiceRepository;
         }
 
-        public void Notify(InvoiceEntity invoice)
+        async Task Notify(InvoiceEntity invoice)
         {
+            CancellationTokenSource cts = new CancellationTokenSource(10000);
+            try
+            {
+                await SendNotification(invoice, cts.Token);
+                return;
+            }
+            catch // It fails, it is OK because we try with hangfire after
+            {
+            }
             var invoiceStr = NBitcoin.JsonConverters.Serializer.ToString(new ScheduledJob() { TryCount = 0, Invoice = invoice });
             if (!string.IsNullOrEmpty(invoice.NotificationURL))
                 _JobClient.Schedule(() => NotifyHttp(invoiceStr), TimeSpan.Zero);
@@ -70,31 +88,7 @@ namespace BTCPayServer.Services.Invoices
             CancellationTokenSource cts = new CancellationTokenSource(10000);
             try
             {
-                var request = new HttpRequestMessage();
-                request.Method = HttpMethod.Post;
-
-                var dto = job.Invoice.EntityToDTO();
-                InvoicePaymentNotification notification = new InvoicePaymentNotification()
-                {
-                    Id = dto.Id,
-                    Url = dto.Url,
-                    BTCDue = dto.BTCDue,
-                    BTCPaid = dto.BTCPaid,
-                    BTCPrice = dto.BTCPrice,
-                    Currency = dto.Currency,
-                    CurrentTime = dto.CurrentTime,
-                    ExceptionStatus = dto.ExceptionStatus,
-                    ExpirationTime = dto.ExpirationTime,
-                    InvoiceTime = dto.InvoiceTime,
-                    PosData = dto.PosData,
-                    Price = dto.Price,
-                    Rate = dto.Rate,
-                    Status = dto.Status,
-                    BuyerFields = job.Invoice.RefundMail == null ? null : new Newtonsoft.Json.Linq.JObject() { new JProperty("buyerEmail", job.Invoice.RefundMail) }
-                };
-                request.RequestUri = new Uri(job.Invoice.NotificationURL, UriKind.Absolute);
-                request.Content = new StringContent(JsonConvert.SerializeObject(notification), Encoding.UTF8, "application/json");
-                var response = await _Client.SendAsync(request, cts.Token);
+                HttpResponseMessage response = await SendNotification(job.Invoice, cts.Token);
                 reschedule = response.StatusCode != System.Net.HttpStatusCode.OK;
                 Logger.LogInformation("Job " + jobId + " returned " + response.StatusCode);
             }
@@ -116,11 +110,73 @@ namespace BTCPayServer.Services.Invoices
             }
         }
 
+        private static async Task<HttpResponseMessage> SendNotification(InvoiceEntity invoice, CancellationToken cancellation)
+        {
+            var request = new HttpRequestMessage();
+            request.Method = HttpMethod.Post;
+
+            var dto = invoice.EntityToDTO();
+            InvoicePaymentNotification notification = new InvoicePaymentNotification()
+            {
+                Id = dto.Id,
+                Url = dto.Url,
+                BTCDue = dto.BTCDue,
+                BTCPaid = dto.BTCPaid,
+                BTCPrice = dto.BTCPrice,
+                Currency = dto.Currency,
+                CurrentTime = dto.CurrentTime,
+                ExceptionStatus = dto.ExceptionStatus,
+                ExpirationTime = dto.ExpirationTime,
+                InvoiceTime = dto.InvoiceTime,
+                PosData = dto.PosData,
+                Price = dto.Price,
+                Rate = dto.Rate,
+                Status = dto.Status,
+                BuyerFields = invoice.RefundMail == null ? null : new Newtonsoft.Json.Linq.JObject() { new JProperty("buyerEmail", invoice.RefundMail) }
+            };
+            request.RequestUri = new Uri(invoice.NotificationURL, UriKind.Absolute);
+            request.Content = new StringContent(JsonConvert.SerializeObject(notification), Encoding.UTF8, "application/json");
+            var response = await _Client.SendAsync(request, cancellation);
+            return response;
+        }
+
         int MaxTry = 6;
 
         private static string GetHttpJobId(InvoiceEntity invoice)
         {
             return $"{invoice.Id}-{invoice.Status}-HTTP";
         }
+
+        CompositeDisposable leases = new CompositeDisposable();
+        public Task StartAsync(CancellationToken cancellationToken)
+        {
+            leases.Add(_EventAggregator.Subscribe<InvoiceStatusChangedEvent>(async e => 
+            {
+                var invoice = await _InvoiceRepository.GetInvoice(null, e.InvoiceId);
+
+                // we need to use the status in the event and not in the invoice. The invoice might now be in another status.
+                if (invoice.FullNotifications)
+                {
+                    if (e.NewState == "expired" ||
+                       e.NewState == "paid" ||
+                       e.NewState == "invalid" ||
+                       e.NewState == "complete"
+                     )
+                        await Notify(invoice);
+                }
+                
+                if(e.NewState == "confirmed")
+                {
+                    await Notify(invoice);
+                }
+            }));
+            return Task.CompletedTask;
+        }
+
+        public Task StopAsync(CancellationToken cancellationToken)
+        {
+            leases.Dispose();
+            return Task.CompletedTask;
+        }
     }
 }

BTCPayServer/Services/Invoices/InvoiceWatcher.cs

@@ -13,6 +13,8 @@ using Microsoft.Extensions.Hosting;
 using System.Collections.Concurrent;
 using Hangfire;
 using BTCPayServer.Services.Wallets;
+using BTCPayServer.Controllers;
+using BTCPayServer.Events;
 
 namespace BTCPayServer.Services.Invoices
 {
@@ -25,14 +27,14 @@ namespace BTCPayServer.Services.Invoices
         InvoiceRepository _InvoiceRepository;
         ExplorerClient _ExplorerClient;
         DerivationStrategyFactory _DerivationFactory;
-        InvoiceNotificationManager _NotificationManager;
+        EventAggregator _EventAggregator;
         BTCPayWallet _Wallet;
         
 
         public InvoiceWatcher(ExplorerClient explorerClient,
             InvoiceRepository invoiceRepository,
+            EventAggregator eventAggregator,
             BTCPayWallet wallet,
-            InvoiceNotificationManager notificationManager,
             InvoiceWatcherAccessor accessor)
         {
             LongPollingMode = explorerClient.Network == Network.RegTest;
@@ -41,23 +43,24 @@ namespace BTCPayServer.Services.Invoices
             _ExplorerClient = explorerClient ?? throw new ArgumentNullException(nameof(explorerClient));
             _DerivationFactory = new DerivationStrategyFactory(_ExplorerClient.Network);
             _InvoiceRepository = invoiceRepository ?? throw new ArgumentNullException(nameof(invoiceRepository));
-            _NotificationManager = notificationManager ?? throw new ArgumentNullException(nameof(notificationManager));
+            _EventAggregator = eventAggregator ?? throw new ArgumentNullException(nameof(eventAggregator));
             accessor.Instance = this;
         }
+        CompositeDisposable leases = new CompositeDisposable();
 
         public bool LongPollingMode
         {
             get; set;
         }
 
-        public async Task NotifyReceived(Script scriptPubKey)
+        async Task NotifyReceived(Script scriptPubKey)
         {
             var invoice = await _InvoiceRepository.GetInvoiceIdFromScriptPubKey(scriptPubKey);
             if (invoice != null)
                 _WatchRequests.Add(invoice);
         }
 
-        public async Task NotifyBlock()
+        async Task NotifyBlock()
         {
             foreach (var invoice in await _InvoiceRepository.GetPendingInvoices())
             {
@@ -76,17 +79,24 @@ namespace BTCPayServer.Services.Invoices
                     if (invoice == null)
                         break;
                     var stateBefore = invoice.Status;
-                    var result = await UpdateInvoice(changes, invoice).ConfigureAwait(false);
+                    var stateChanges = new List<string>();
+                    var result = await UpdateInvoice(changes, invoice, stateChanges).ConfigureAwait(false);
                     changes = result.Changes;
                     if (result.NeedSave)
+                    { 
                         await _InvoiceRepository.UpdateInvoiceStatus(invoice.Id, invoice.Status, invoice.ExceptionStatus).ConfigureAwait(false);
-
-                    var changed = stateBefore != invoice.Status;
-                    if (changed)
-                    {
-                        Logs.PayServer.LogInformation($"Invoice {invoice.Id}: {stateBefore} => {invoice.Status}");
+                        _EventAggregator.Publish(new InvoiceDataChangedEvent() { InvoiceId = invoice.Id });
                     }
 
+                    var changed = stateBefore != invoice.Status;
+
+                    foreach(var stateChange in stateChanges)
+                    {
+                        _EventAggregator.Publish(new InvoiceStatusChangedEvent() { InvoiceId = invoice.Id, NewState = stateChange, OldState = stateBefore });
+                        stateBefore = stateChange;
+                    }
+
+                    
                     if (invoice.Status == "complete" ||
                        ((invoice.Status == "invalid" || invoice.Status == "expired") && invoice.MonitoringExpiration < DateTimeOffset.UtcNow))
                     {
@@ -111,7 +121,7 @@ namespace BTCPayServer.Services.Invoices
         }
 
 
-        private async Task<(bool NeedSave, UTXOChanges Changes)> UpdateInvoice(UTXOChanges changes, InvoiceEntity invoice)
+        private async Task<(bool NeedSave, UTXOChanges Changes)> UpdateInvoice(UTXOChanges changes, InvoiceEntity invoice, List<string> stateChanges)
         {
             bool needSave = false;
             //Fetch unknown payments
@@ -139,10 +149,7 @@ namespace BTCPayServer.Services.Invoices
                 needSave = true;
                 await _InvoiceRepository.UnaffectAddress(invoice.Id);
                 invoice.Status = "expired";
-                if (invoice.FullNotifications)
-                {
-                    _NotificationManager.Notify(invoice);
-                }
+                stateChanges.Add(invoice.Status);
             }
 
             if (invoice.Status == "new" || invoice.Status == "expired")
@@ -153,10 +160,7 @@ namespace BTCPayServer.Services.Invoices
                     if (invoice.Status == "new")
                     {
                         invoice.Status = "paid";
-                        if (invoice.FullNotifications)
-                        {
-                            _NotificationManager.Notify(invoice);
-                        }
+                        stateChanges.Add(invoice.Status);
                         invoice.ExceptionStatus = null;
                         await _InvoiceRepository.UnaffectAddress(invoice.Id);
                         needSave = true;
@@ -216,11 +220,8 @@ namespace BTCPayServer.Services.Invoices
                 {
                     await _InvoiceRepository.UnaffectAddress(invoice.Id);
                     invoice.Status = "invalid";
+                    stateChanges.Add(invoice.Status);
                     needSave = true;
-                    if (invoice.FullNotifications)
-                    {
-                        _NotificationManager.Notify(invoice);
-                    }
                 }
                 else
                 {
@@ -229,7 +230,7 @@ namespace BTCPayServer.Services.Invoices
                     {
                         await _InvoiceRepository.UnaffectAddress(invoice.Id);
                         invoice.Status = "confirmed";
-                        _NotificationManager.Notify(invoice);
+                        stateChanges.Add(invoice.Status);
                         needSave = true;
                     }
                 }
@@ -243,8 +244,7 @@ namespace BTCPayServer.Services.Invoices
                 if (totalConfirmed >= invoice.GetTotalCryptoDue())
                 {
                     invoice.Status = "complete";
-                    if (invoice.FullNotifications)
-                        _NotificationManager.Notify(invoice);
+                    stateChanges.Add(invoice.Status);
                     needSave = true;
                 }
             }
@@ -356,6 +356,10 @@ namespace BTCPayServer.Services.Invoices
                     _WatchRequests.Add(pending);
                 }
             }, null, 0, (int)PollInterval.TotalMilliseconds);
+
+            leases.Add(_EventAggregator.Subscribe<NewBlockEvent>(async b => { await NotifyBlock(); }));
+            leases.Add(_EventAggregator.Subscribe<TxOutReceivedEvent>(async b => { await NotifyReceived(b.ScriptPubKey); }));
+
             return Task.CompletedTask;
         }
 
@@ -402,6 +406,7 @@ namespace BTCPayServer.Services.Invoices
 
         public Task StopAsync(CancellationToken cancellationToken)
         {
+            leases.Dispose();
             _UpdatePendingInvoices.Dispose();
             _Cts.Cancel();
             return Task.WhenAny(_RunningTask.Task, Task.Delay(-1, cancellationToken));