Gating host specialization on WEBSITE_CONFIGURATION_READY (#2867)

Author: mathewc

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

@@ -137,7 +137,7 @@ internal void EnsureInitialized(WebHostSettings settings)
                     // 1) We _were_ in standby mode and now we're ready to specialize
                     // 2) We're doing non-specialization normal initialization
                     if (_activeHostManager == null && 
-                        (_standbyHostManager == null || _settingsManager.ContainerReady))
+                        (_standbyHostManager == null || (_settingsManager.ContainerReady && _settingsManager.ConfigurationReady)))
                     {
                         _specializationTimer?.Dispose();
                         _specializationTimer = null;
@@ -290,12 +290,12 @@ private void OnSpecializationTimerTick(object state)
         {
             EnsureInitialized((WebHostSettings)state);
 
-            // We know we've just specialized, since this timer only runs
-            // when in standby mode. We want to initialize the host manager
-            // immediately. Note that the host might also be initialized
-            // concurrently  by incoming http requests, but the initialization
-            // here ensures that it takes place in the absence of any http
-            // traffic.
+            // If the active manager is not null, we know we've just specialized,
+            // since this timer only runs when in standby mode. We want to initialize
+            // the host manager immediately.
+            // Note that the host might also be initialized concurrently by incoming
+            // http requests, but the initialization here ensures that it takes place
+            // in the absence of any http traffic.
             _activeHostManager?.EnsureInitialized();
         }
 

src/WebJobs.Script/Config/ScriptSettingsManager.cs

@@ -28,6 +28,8 @@ public static ScriptSettingsManager Instance
 
         public virtual bool ContainerReady => !string.IsNullOrEmpty(GetSetting(EnvironmentSettingNames.AzureWebsiteContainerReady));
 
+        public virtual bool ConfigurationReady => !string.IsNullOrEmpty(GetSetting(EnvironmentSettingNames.AzureWebsiteConfigurationReady));
+
         public string WebsiteSku => GetSetting(EnvironmentSettingNames.AzureWebsiteSku);
 
         public bool IsDynamicSku => WebsiteSku == ScriptConstants.DynamicSku;

src/WebJobs.Script/EnvironmentSettingNames.cs

@@ -14,7 +14,6 @@ public static class EnvironmentSettingNames
         public const string AzureWebsiteZipDeployment = "WEBSITE_USE_ZIP";
         public const string RemoteDebuggingPort = "REMOTEDEBUGGINGPORT";
         public const string AzureWebsitePlaceholderMode = "WEBSITE_PLACEHOLDER_MODE";
-        public const string AzureWebsiteContainerReady = "WEBSITE_CONTAINER_READY";
         public const string AzureWebsiteHomePath = "HOME";
         public const string AzureWebJobsScriptRoot = "AzureWebJobsScriptRoot";
         public const string CompilationReleaseMode = "AzureWebJobsDotNetReleaseCompilation";
@@ -26,5 +25,18 @@ public static class EnvironmentSettingNames
         public const string AppInsightsInstrumentationKey = "APPINSIGHTS_INSTRUMENTATIONKEY";
         public const string ProxySiteExtensionEnabledKey = "ROUTING_EXTENSION_VERSION";
         public const string FunctionsExtensionVersion = "FUNCTIONS_EXTENSION_VERSION";
+
+        /// <summary>
+        /// Environment variable dynamically set by the platform when it is safe to
+        /// start specializing the host instance (e.g. file system is ready, etc.)
+        /// </summary>
+        public const string AzureWebsiteContainerReady = "WEBSITE_CONTAINER_READY";
+
+        /// <summary>
+        /// Environment variable dynamically set by the platform when configuration has been
+        /// completely initialized (e.g. EnvSettings module has ran) and it is safe to read
+        /// configuration values.
+        /// </summary>
+        public const string AzureWebsiteConfigurationReady = "WEBSITE_CONFIGURATION_READY";
     }
 }

test/WebJobs.Script.Tests.Integration/Host/StandbyManagerTests.cs

@@ -66,6 +66,7 @@ public async Task StandbyMode_EndToEnd()
             {
                 { EnvironmentSettingNames.AzureWebsitePlaceholderMode, "1" },
                 { EnvironmentSettingNames.AzureWebsiteContainerReady, null },
+                { EnvironmentSettingNames.AzureWebsiteConfigurationReady, null },
                 { EnvironmentSettingNames.AzureWebsiteInstanceId, "87654639876900123453445678890144" }
             };
             using (var env = new TestScopedEnvironmentVariable(vars))
@@ -114,6 +115,7 @@ public async Task StandbyMode_EndToEnd()
                 // Now specialize the host
                 ScriptSettingsManager.Instance.SetSetting(EnvironmentSettingNames.AzureWebsitePlaceholderMode, "0");
                 ScriptSettingsManager.Instance.SetSetting(EnvironmentSettingNames.AzureWebsiteContainerReady, "1");
+                ScriptSettingsManager.Instance.SetSetting(EnvironmentSettingNames.AzureWebsiteConfigurationReady, "1");
 
                 // give time for the specialization to happen
                 string[] logLines = null;

test/WebJobs.Script.Tests.Integration/Host/StandbyModeTests.cs

@@ -117,6 +117,7 @@ public void EnsureInitialized_PlaceholderMode()
 
                 _settingsManager.SetSetting(EnvironmentSettingNames.AzureWebsitePlaceholderMode, "0");
                 _settingsManager.SetSetting(EnvironmentSettingNames.AzureWebsiteContainerReady, "1");
+                _settingsManager.SetSetting(EnvironmentSettingNames.AzureWebsiteConfigurationReady, "1");
                 Assert.False(WebScriptHostManager.InStandbyMode);
                 _webHostResolver.EnsureInitialized(settings);
 
@@ -144,6 +145,7 @@ private void TestGetter<T>(Func<WebHostSettings, T> func)
 
                     _settingsManager.SetSetting(EnvironmentSettingNames.AzureWebsitePlaceholderMode, "0");
                     _settingsManager.SetSetting(EnvironmentSettingNames.AzureWebsiteContainerReady, "1");
+                    _settingsManager.SetSetting(EnvironmentSettingNames.AzureWebsiteConfigurationReady, "1");
                     current = func(settings);
                     Assert.NotNull(current);
                     Assert.NotSame(prev, current);