From 154b59c84b9f365391e381405b6dcc0da3031d9d Mon Sep 17 00:00:00 2001
From: Stephan <stephane@umbraco.dk>
Date: Mon, 11 Feb 2019 14:09:40 +0100
Subject: [PATCH] Fix redirect tracking

---
 .../Routing/RedirectTrackingComponent.cs      | 36 ++++++++++++-------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/src/Umbraco.Web/Routing/RedirectTrackingComponent.cs b/src/Umbraco.Web/Routing/RedirectTrackingComponent.cs
index c49dffd6e4..acbd022f2e 100644
--- a/src/Umbraco.Web/Routing/RedirectTrackingComponent.cs
+++ b/src/Umbraco.Web/Routing/RedirectTrackingComponent.cs
@@ -38,16 +38,24 @@ namespace Umbraco.Web.Routing
         {
             get
             {
-                var oldRoutes =
-                    (Dictionary<ContentIdAndCulture, ContentKeyAndOldRoute>) UmbracoContext.Current.HttpContext.Items[
-                        ContextKey3];
+                var oldRoutes = (Dictionary<ContentIdAndCulture, ContentKeyAndOldRoute>) UmbracoContext.Current.HttpContext.Items[ContextKey3];
                 if (oldRoutes == null)
-                    UmbracoContext.Current.HttpContext.Items[ContextKey3] =
-                        oldRoutes = new Dictionary<ContentIdAndCulture, ContentKeyAndOldRoute>();
+                    UmbracoContext.Current.HttpContext.Items[ContextKey3] = oldRoutes = new Dictionary<ContentIdAndCulture, ContentKeyAndOldRoute>();
                 return oldRoutes;
             }
         }
 
+        private static bool HasOldRoutes
+        {
+            get
+            {
+                if (Current.UmbracoContext == null) return false;
+                if (Current.UmbracoContext.HttpContext == null) return false;
+                if (Current.UmbracoContext.HttpContext.Items[ContextKey3] == null) return false;
+                return true;
+            }
+        }
+
         private static bool LockedEvents
         {
             get => Moving && UmbracoContext.Current.HttpContext.Items[ContextKey2] != null;
@@ -97,8 +105,8 @@ namespace Umbraco.Web.Routing
             ContentService.Published += ContentService_Published;
             ContentService.Moving += ContentService_Moving;
             ContentService.Moved += ContentService_Moved;
-            ContentCacheRefresher.CacheUpdated += ContentCacheRefresher_CacheUpdated;
 
+            ContentCacheRefresher.CacheUpdated += ContentCacheRefresher_CacheUpdated;
 
             // kill all redirects once a content is deleted
             //ContentService.Deleted += ContentService_Deleted;
@@ -111,21 +119,26 @@ namespace Umbraco.Web.Routing
         public void Terminate()
         { }
 
-        private static void ContentCacheRefresher_CacheUpdated(ContentCacheRefresher sender,
-            CacheRefresherEventArgs args)
+        private static void ContentCacheRefresher_CacheUpdated(ContentCacheRefresher sender, CacheRefresherEventArgs args)
         {
+            // that event is a distributed even that triggers on all nodes
+            // BUT it should totally NOT run on nodes other that the one that handled the other events
+            // and besides, it cannot run on a background thread!
+            if (!HasOldRoutes)
+                return;
+
             // sanity checks
             if (args.MessageType != MessageType.RefreshByPayload)
             {
                 throw new InvalidOperationException("ContentCacheRefresher MessageType should be ByPayload.");
             }
+
             if (args.MessageObject == null)
             {
                 return;
             }
 
-            var payloads = args.MessageObject as ContentCacheRefresher.JsonPayload[];
-            if (payloads == null)
+            if (!(args.MessageObject is ContentCacheRefresher.JsonPayload[]))
             {
                 throw new InvalidOperationException("ContentCacheRefresher MessageObject should be JsonPayload[].");
             }
@@ -137,8 +150,7 @@ namespace Umbraco.Web.Routing
             {
                 // assuming we cannot have 'CacheUpdated' for only part of the infos else we'd need
                 // to set a flag in 'Published' to indicate which entities have been refreshed ok
-                CreateRedirect(oldRoute.Key.ContentId, oldRoute.Key.Culture, oldRoute.Value.ContentKey,
-                    oldRoute.Value.OldRoute);
+                CreateRedirect(oldRoute.Key.ContentId, oldRoute.Key.Culture, oldRoute.Value.ContentKey, oldRoute.Value.OldRoute);
                 removeKeys.Add(oldRoute.Key);
             }