Fixing host specialization tracing

Author: mathewc

src/WebJobs.Script.WebHost/App_Start/WebHostResolver.cs

@@ -8,6 +8,7 @@
 using Microsoft.Azure.WebJobs.Script.Config;
 using Microsoft.Azure.WebJobs.Script.Diagnostics;
 using Microsoft.Azure.WebJobs.Script.Eventing;
+using Microsoft.Azure.WebJobs.Script.WebHost.Properties;
 using Microsoft.Azure.WebJobs.Script.WebHost.WebHooks;
 
 namespace Microsoft.Azure.WebJobs.Script.WebHost
@@ -95,7 +96,7 @@ public WebHookReceiverManager GetWebHookReceiverManager(WebHostSettings settings
             }
         }
 
-        private void EnsureInitialized(WebHostSettings settings)
+        internal void EnsureInitialized(WebHostSettings settings)
         {
             if (!WebScriptHostManager.InStandbyMode)
             {
@@ -108,9 +109,12 @@ private void EnsureInitialized(WebHostSettings settings)
                     _activeReceiverManager = new WebHookReceiverManager(_activeHostManager.SecretManager);
                     InitializeFileSystem();
 
-                    // here we're undergoing the one and only one
-                    // standby mode specialization
-                    _activeScriptHostConfig.TraceWriter.Info("Host has been specialized");
+                    if (_standbyHostManager != null)
+                    {
+                        // we're undergoing the one and only one
+                        // standby mode specialization
+                        _activeScriptHostConfig.TraceWriter.Info(Resources.HostSpecializationTrace);
+                    }
 
                     _standbyHostManager?.Dispose();
                     _standbyReceiverManager?.Dispose();

src/WebJobs.Script.WebHost/Properties/Resources.Designer.cs

@@ -259,6 +259,9 @@
     ]
 }</value>
   </data>
+  <data name="HostSpecializationTrace" xml:space="preserve">
+    <value>Host has been specialized</value>
+  </data>
   <data name="SwaggerFileDeleteError" xml:space="preserve">
     <value>Error deleting Swagger document</value>
   </data>

src/WebJobs.Script.WebHost/Properties/Resources.resx

@@ -8,6 +8,7 @@
 using Microsoft.Azure.WebJobs.Script.Config;
 using Microsoft.Azure.WebJobs.Script.Eventing;
 using Microsoft.Azure.WebJobs.Script.WebHost;
+using Microsoft.Azure.WebJobs.Script.WebHost.Properties;
 using Moq;
 using Xunit;
 
@@ -87,6 +88,48 @@ public void GetWebScriptHostManager_ReturnsExpectedValue()
             TestGetter(_webHostResolver.GetWebScriptHostManager);
         }
 
+        [Fact]
+        public void EnsureInitialized_NonPlaceholderMode()
+        {
+            using (new TestEnvironment())
+            {
+                _traceWriter.Traces.Clear();
+
+                var settings = GetWebHostSettings();
+                _settingsManager.SetSetting(EnvironmentSettingNames.AzureWebsitePlaceholderMode, "0");
+                Assert.False(WebScriptHostManager.InStandbyMode);
+                _webHostResolver.EnsureInitialized(settings);
+
+                // ensure specialization message is NOT written
+                var traces = _traceWriter.Traces.ToArray();
+                var traceEvent = traces.SingleOrDefault(p => p.Message.Contains(Resources.HostSpecializationTrace));
+                Assert.Null(traceEvent);
+            }
+        }
+
+        [Fact]
+        public void EnsureInitialized_PlaceholderMode()
+        {
+            using (new TestEnvironment())
+            {
+                _traceWriter.Traces.Clear();
+
+                var settings = GetWebHostSettings();
+                _settingsManager.SetSetting(EnvironmentSettingNames.AzureWebsitePlaceholderMode, "1");
+                Assert.True(WebScriptHostManager.InStandbyMode);
+                _webHostResolver.EnsureInitialized(settings);
+
+                _settingsManager.SetSetting(EnvironmentSettingNames.AzureWebsitePlaceholderMode, "0");
+                Assert.False(WebScriptHostManager.InStandbyMode);
+                _webHostResolver.EnsureInitialized(settings);
+
+                var traces = _traceWriter.Traces.ToArray();
+                var traceEvent = traces.Last();
+                Assert.Equal(Resources.HostSpecializationTrace, traceEvent.Message);
+                Assert.Equal(TraceLevel.Info, traceEvent.Level);
+            }
+        }
+
         private void TestGetter<T>(Func<WebHostSettings, T> func)
         {
             using (new TestEnvironment())
@@ -96,8 +139,6 @@ private void TestGetter<T>(Func<WebHostSettings, T> func)
                 T next = default(T);
                 try
                 {
-                    _traceWriter.Traces.Clear();
-
                     _settingsManager.SetSetting(EnvironmentSettingNames.AzureWebsitePlaceholderMode, "1");
 
                     var settings = GetWebHostSettings();
@@ -109,11 +150,6 @@ private void TestGetter<T>(Func<WebHostSettings, T> func)
                     Assert.NotNull(current);
                     Assert.NotSame(prev, current);
 
-                    var traces = _traceWriter.Traces.ToArray();
-                    var traceEvent = traces.Last();
-                    Assert.Equal("Host has been specialized", traceEvent.Message);
-                    Assert.Equal(TraceLevel.Info, traceEvent.Level);
-
                     // test only set one way
                     _settingsManager.SetSetting(EnvironmentSettingNames.AzureWebsitePlaceholderMode, "1");
                     next = func(settings);