From 67038ddd5e44e3b91005eee34a6b5e055ed0e3e1 Mon Sep 17 00:00:00 2001
From: Taloth Saldono <Taloth@users.noreply.github.com>
Date: Thu, 15 Mar 2018 22:48:05 +0100
Subject: [PATCH] Cache EventAggregator Subscribers.

---
 .../Messaging/Events/EventAggregator.cs       | 49 ++++++++++++++++---
 1 file changed, 42 insertions(+), 7 deletions(-)

diff --git a/src/NzbDrone.Core/Messaging/Events/EventAggregator.cs b/src/NzbDrone.Core/Messaging/Events/EventAggregator.cs
index f447cf237..4f49324a9 100644
--- a/src/NzbDrone.Core/Messaging/Events/EventAggregator.cs
+++ b/src/NzbDrone.Core/Messaging/Events/EventAggregator.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using NLog;
@@ -14,12 +15,38 @@ namespace NzbDrone.Core.Messaging.Events
         private readonly Logger _logger;
         private readonly IServiceFactory _serviceFactory;
         private readonly TaskFactory _taskFactory;
+        private readonly Dictionary<string, object> _eventSubscribers;
+
+        private class EventSubscribers<TEvent> where TEvent : class, IEvent
+        {
+            private IServiceFactory _serviceFactory;
+
+            public IHandle<TEvent>[] _syncHandlers;
+            public IHandleAsync<TEvent>[] _asyncHandlers;
+            public IHandleAsync<IEvent>[] _globalHandlers;
+
+            public EventSubscribers(IServiceFactory serviceFactory)
+            {
+                _serviceFactory = serviceFactory;
+
+                _syncHandlers = serviceFactory.BuildAll<IHandle<TEvent>>()
+                                              .OrderBy(GetEventHandleOrder)
+                                              .ToArray();
+
+                _globalHandlers = serviceFactory.BuildAll<IHandleAsync<IEvent>>()
+                                              .ToArray();
+
+                _asyncHandlers = serviceFactory.BuildAll<IHandleAsync<TEvent>>()
+                                               .ToArray();
+            }
+        }
 
         public EventAggregator(Logger logger, IServiceFactory serviceFactory)
         {
             _logger = logger;
             _serviceFactory = serviceFactory;
             _taskFactory = new TaskFactory();
+            _eventSubscribers = new Dictionary<string, object>();
         }
 
         public void PublishEvent<TEvent>(TEvent @event) where TEvent : class, IEvent
@@ -47,12 +74,20 @@ namespace NzbDrone.Core.Messaging.Events
 
             _logger.Trace("Publishing {0}", eventName);
 
+            EventSubscribers<TEvent> subscribers;
+            lock (_eventSubscribers)
+            {
+                object target;
+                if (!_eventSubscribers.TryGetValue(eventName, out target))
+                {
+                    _eventSubscribers[eventName] = target = new EventSubscribers<TEvent>(_serviceFactory);
+                }
+
+                subscribers = target as EventSubscribers<TEvent>;
+            }
 
             //call synchronous handlers first.
-            var handlers = _serviceFactory.BuildAll<IHandle<TEvent>>()
-                                          .OrderBy(GetEventHandleOrder)
-                                          .ToList();
-
+            var handlers = subscribers._syncHandlers;
             foreach (var handler in handlers)
             {
                 try
@@ -67,7 +102,7 @@ namespace NzbDrone.Core.Messaging.Events
                 }
             }
 
-            foreach (var handler in _serviceFactory.BuildAll<IHandleAsync<IEvent>>())
+            foreach (var handler in subscribers._globalHandlers)
             {
                 var handlerLocal = handler;
 
@@ -78,7 +113,7 @@ namespace NzbDrone.Core.Messaging.Events
                 .LogExceptions();
             }
 
-            foreach (var handler in _serviceFactory.BuildAll<IHandleAsync<TEvent>>())
+            foreach (var handler in subscribers._asyncHandlers)
             {
                 var handlerLocal = handler;
 
@@ -102,7 +137,7 @@ namespace NzbDrone.Core.Messaging.Events
             return string.Format("{0}<{1}>", eventType.Name.Remove(eventType.Name.IndexOf('`')), eventType.GetGenericArguments()[0].Name);
         }
 
-        private int GetEventHandleOrder<TEvent>(IHandle<TEvent> eventHandler) where TEvent : class, IEvent
+        internal static int GetEventHandleOrder<TEvent>(IHandle<TEvent> eventHandler) where TEvent : class, IEvent
         {
             // TODO: Convert "Handle" to nameof(eventHandler.Handle) after .net 4.5
             var method = eventHandler.GetType().GetMethod("Handle", new Type[] {typeof(TEvent)});