From e8cb30fbc4cb5ee71aec1ed5a6e29b7681aed8ab Mon Sep 17 00:00:00 2001
From: Stephan <stephane@umbraco.dk>
Date: Fri, 25 Jan 2019 12:33:20 +0100
Subject: [PATCH] Fix exception when replacing IServerRegistrar

---
 .../Runtime/CoreRuntimeComposer.cs            | 18 ++++++----
 ...aseServerRegistrarAndMessengerComponent.cs | 36 ++++++++++++-------
 2 files changed, 35 insertions(+), 19 deletions(-)

diff --git a/src/Umbraco.Core/Runtime/CoreRuntimeComposer.cs b/src/Umbraco.Core/Runtime/CoreRuntimeComposer.cs
index 5535d5c67b..83cc456127 100644
--- a/src/Umbraco.Core/Runtime/CoreRuntimeComposer.cs
+++ b/src/Umbraco.Core/Runtime/CoreRuntimeComposer.cs
@@ -73,16 +73,20 @@ namespace Umbraco.Core.Runtime
             // register a server registrar, by default it's the db registrar
             composition.RegisterUnique<IServerRegistrar>(f =>
             {
-                if ("true".InvariantEquals(ConfigurationManager.AppSettings["umbracoDisableElectionForSingleServer"]))
-                    return new SingleServerRegistrar(f.GetInstance<IRuntimeState>());
-                return new DatabaseServerRegistrar(
-                    new Lazy<IServerRegistrationService>(f.GetInstance<IServerRegistrationService>),
-                    new DatabaseServerRegistrarOptions());
+                // TODO this is a hack, use proper configuration!
+                // also: we still register the full IServerMessenger because
+                // even on 1 single server we can have 2 concurrent app domains
+                var singleServer = "true".InvariantEquals(ConfigurationManager.AppSettings["umbracoDisableElectionForSingleServer"]);
+                return singleServer
+                    ? (IServerRegistrar) new SingleServerRegistrar(f.GetInstance<IRuntimeState>())
+                    : new DatabaseServerRegistrar(
+                        new Lazy<IServerRegistrationService>(f.GetInstance<IServerRegistrationService>),
+                        new DatabaseServerRegistrarOptions());
             });
 
             // by default we'll use the database server messenger with default options (no callbacks),
-            // this will be overridden by either the legacy thing or the db thing in the corresponding
-            // components in the web project - todo - should obsolete the legacy thing
+            // this will be overridden by the db thing in the corresponding components in the web
+            // project
             composition.RegisterUnique<IServerMessenger>(factory
                 => new DatabaseServerMessenger(
                     factory.GetInstance<IRuntimeState>(),
diff --git a/src/Umbraco.Web/Components/DatabaseServerRegistrarAndMessengerComponent.cs b/src/Umbraco.Web/Components/DatabaseServerRegistrarAndMessengerComponent.cs
index 2e3132a82c..589502e6a2 100644
--- a/src/Umbraco.Web/Components/DatabaseServerRegistrarAndMessengerComponent.cs
+++ b/src/Umbraco.Web/Components/DatabaseServerRegistrarAndMessengerComponent.cs
@@ -106,30 +106,36 @@ namespace Umbraco.Web.Components
 
         public DatabaseServerRegistrarAndMessengerComponent(IRuntimeState runtime, IServerRegistrar serverRegistrar, IServerMessenger serverMessenger, IServerRegistrationService registrationService, ILogger logger, IndexRebuilder indexRebuilder)
         {
-            _registrar = serverRegistrar as DatabaseServerRegistrar;
-            if (_registrar == null) throw new Exception("panic: registar.");
-
-            _messenger = serverMessenger as BatchedDatabaseServerMessenger;
-            if (_messenger == null) throw new Exception("panic: messenger");
-
             _runtime = runtime;
             _logger = logger;
             _registrationService = registrationService;
             _indexRebuilder = indexRebuilder;
 
-            _touchTaskRunner = new BackgroundTaskRunner<IBackgroundTask>("ServerRegistration",
-                new BackgroundTaskRunnerOptions { AutoStart = true }, logger);
-            _processTaskRunner = new BackgroundTaskRunner<IBackgroundTask>("ServerInstProcess",
-                new BackgroundTaskRunnerOptions { AutoStart = true }, logger);
+            // create task runner for DatabaseServerRegistrar
+            _registrar = serverRegistrar as DatabaseServerRegistrar;
+            if (_registrar != null)
+            {
+                _touchTaskRunner = new BackgroundTaskRunner<IBackgroundTask>("ServerRegistration",
+                    new BackgroundTaskRunnerOptions { AutoStart = true }, logger);
+            }
+
+            // create task runner for BatchedDatabaseServerMessenger
+            _messenger = serverMessenger as BatchedDatabaseServerMessenger;
+            if (_messenger != null)
+            {
+                _processTaskRunner = new BackgroundTaskRunner<IBackgroundTask>("ServerInstProcess",
+                    new BackgroundTaskRunnerOptions { AutoStart = true }, logger);
+            }
         }
 
         public void Initialize()
         { 
             //We will start the whole process when a successful request is made
-            UmbracoModule.RouteAttempt += RegisterBackgroundTasksOnce;
+            if (_registrar != null || _messenger != null)
+                UmbracoModule.RouteAttempt += RegisterBackgroundTasksOnce;
 
             // must come last, as it references some _variables
-            _messenger.Startup();
+            _messenger?.Startup();
         }
 
         public void Terminate()
@@ -175,6 +181,9 @@ namespace Umbraco.Web.Components
 
         private IBackgroundTask RegisterInstructionProcess()
         {
+            if (_messenger == null)
+                return null;
+
             var task = new InstructionProcessTask(_processTaskRunner,
                 60000, //delay before first execution
                 _messenger.Options.ThrottleSeconds*1000, //amount of ms between executions
@@ -186,6 +195,9 @@ namespace Umbraco.Web.Components
 
         private IBackgroundTask RegisterTouchServer(IServerRegistrationService registrationService, string serverAddress)
         {
+            if (_registrar == null)
+                return null;
+
             var task = new TouchServerTask(_touchTaskRunner,
                 15000, //delay before first execution
                 _registrar.Options.RecurringSeconds*1000, //amount of ms between executions