Harden code against System.AppDomainUnloadedException - Attempted t…

…o access an unloaded AppDomain. (#47) `AppDomainUnloadedException` thrown from `Server.Host.ServerHost.UnloadAllServers()` if an AppDomain has already been unloaded / disposed. Failure mode: ``` TestCleanup method Tests.ClusterTests.TestCleanup threw exception. System.AppDomainUnloadedException: System.AppDomainUnloadedException: Attempted to access an unloaded AppDomain.. at System.AppDomain.get_FriendlyName() at Server.Host.ServerHost.UnloadAllServers() in C:\projects\serverhost\ServerHost\ServerHost.cs:line 132 at Tests.ClusterTests.TestCleanup() in E:\Depot\Internal\DSoAP\Testing\DSoAP.Tests\ClusterTests.cs:line 56 ``` Fixes bug #46 Bump package version to `1.1.12`
jthelin · Oct 3, 2018 · a0cbb1d · a0cbb1d
1 parent fa47c11
commit a0cbb1d
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Showing 3 changed files with 46 additions and 12 deletions.
diff --git a/ServerHost/ServerHost.cs b/ServerHost/ServerHost.cs
@@ -30,7 +30,7 @@ public static class ServerHost
         /// <returns><c>ServerHostHandle</c> object containing metadata about the loaded server instance.</returns>
         /// <remarks>
         /// The <c>serverName</c> will be used for the name of the newly created AppDomain to host this new server instance.
-        /// Multiple copies of a server can be created if they arer each given a different server name.
+        /// Multiple copies of a server can be created if they are each given a different server name.
         /// </remarks>
         public static ServerHostHandle<TServer> LoadServerInNewAppDomain<TServer>(
             string serverName)
@@ -105,15 +105,23 @@ public static void UnloadServerInAppDomain(AppDomain appDomain)
         {
             if (appDomain == null) return;
 
+            string appDomainName = "UNKNOWN";
+
             try
             {
+                appDomainName = appDomain.FriendlyName;
+
                 appDomain.UnhandledException -= ReportUnobservedException;
 
                 AppDomain.Unload(appDomain);
             }
+            catch (CannotUnloadAppDomainException exc)
+            {
+                Log.Warn($"Unable to unload AppDomain {appDomainName} - " + exc.Message, exc);
+            }
             catch (Exception exc)
             {
-                Log.Warn($"Ignoring error unloading AppDomain {appDomain.FriendlyName} - {exc}");
+                Log.Warn($"Ignoring error unloading AppDomain {appDomainName} - " + exc.Message, exc);
             }
         }
 
@@ -122,16 +130,29 @@ public static void UnloadServerInAppDomain(AppDomain appDomain)
         /// </summary>
         public static void UnloadAllServers()
         {
-            foreach (string serverName in LoadedAppDomains.Keys.ToArray()) // Take working copy
+            string[] serverNames = LoadedAppDomains.Keys.ToArray(); // Take working copy
+
+            foreach (string serverName in serverNames)
             {
-                AppDomain appDomain;
-                if (LoadedAppDomains.TryRemove(serverName, out appDomain))
+                if (LoadedAppDomains.TryRemove(serverName, out AppDomain appDomain))
                 {
                     if (appDomain == null) continue;
 
-                    Log.Info($"Unloading Server {serverName} in AppDomain {appDomain.FriendlyName}");
+                    string appDomainName = null;
+                    try
+                    {
+                        // We may get AppDomainUnloadedException thrown here - X-ref: #46.
+
+                        appDomainName = appDomain.FriendlyName;
+
+                        Log.Info($"Unloading Server {serverName} in AppDomain {appDomainName}");
 
-                    UnloadServerInAppDomain(appDomain);
+                        UnloadServerInAppDomain(appDomain);
+                    }
+                    catch (Exception exc)
+                    {
+                        Log.Warn($"Ignoring error unloading AppDomain {appDomainName ?? serverName}. " + exc.Message, exc);
+                    }
                 }
             }
         }

diff --git a/ServerHost/ServerHost.csproj b/ServerHost/ServerHost.csproj
@@ -11,7 +11,7 @@
 
   <PropertyGroup>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
-    <Version>1.1.11</Version>
+    <Version>1.1.12</Version>
     <Authors>Jorgen Thelin</Authors>
     <Copyright>Copyright © Jorgen Thelin 2015-2018</Copyright>
     <Description>ServerHost - A .NET Server Hosting utility library, including in-process server host testing.</Description>
@@ -23,13 +23,13 @@
     <RepositoryUrl>https://github.com/jthelin/ServerHost.git</RepositoryUrl>
   </PropertyGroup>
 
-  <PropertyGroup Condition="'$(TRAVIS)' == 'true'" >
+  <PropertyGroup Condition="'$(TRAVIS)' == 'true'">
     <!-- Disable SourceLink when running Travis-CI build, due to bug. -->
     <!-- https://github.com/dotnet/sourcelink/issues/119 -->
     <EnableSourceLink>false</EnableSourceLink>
   </PropertyGroup>
 
-  <PropertyGroup Condition="'$(TRAVIS)' != 'true'" >
+  <PropertyGroup Condition="'$(TRAVIS)' != 'true'">
 
     <!-- SourceLink settings: https://github.com/dotnet/sourcelink#using-sourcelink -->
 

diff --git a/Tests/Tests.Net46/ServerHostTests.cs b/Tests/Tests.Net46/ServerHostTests.cs
@@ -63,17 +63,30 @@ public async Task UnloadServerInAppDomain()
             ServerHost.LoadServerInNewAppDomain<TestServer.Server>("Two");
             ServerHost.LoadServerInNewAppDomain<TestServer.Server>("Three");
 
-            var unload = Enumerable.Range(1, 4).Select(i =>
+            var unload = Enumerable.Range(1, 10).Select(i =>
             {
                 return Task.Run(async () =>
                 {
-                    await Task.Delay(100 - i);
+                    await Task.Delay(10 - i);
                     ServerHost.UnloadAllServers();
                 });
             });
             await Task.WhenAll(unload);
         }
 
+        [Fact]
+        [Trait("Category", "BVT")]
+        public void UnloadAllAppDomainsTwice()
+        {
+            ServerHost.LoadServerInNewAppDomain<TestServer.Server>("Four");
+            ServerHost.LoadServerInNewAppDomain<TestServer.Server>("Five");
+            ServerHost.LoadServerInNewAppDomain<TestServer.Server>("Six");
+
+            ServerHost.UnloadAllServers();
+
+            ServerHost.UnloadAllServers();
+        }
+
         [Fact]
         [Trait("Category", "BVT")]
         public void ServerHost_Version()