Updating HostWarmupMiddleware to work with placeholder simulation locally. (#9660)

* Updating WarmupMiddleware to work with placeholder simulation locally.

* Update release notes

* run warmup code for HP call when in placeholdersimulation mode.

* Updates to trigger warmup code when home page is requested in placeholder simulation mode.

Author: kshyju

release_notes.md

@@ -26,6 +26,7 @@
 - Upgrading dependent packages to latest versions. #9646
    - Azure.Identity (1.10.0 to 1.10.3)
    - Azure.Core (1.34.0 to 1.35.0)
+- Updating HostWarmupMiddleware to trigger warmup code on home page request when testing locally using DebugPlaceholder or ReleasePlaceholder configuration.
 - Bug fix: Comparisons in the Azure Key Vault Secrets Repository are now case insensitive (#9644)
   - This fixes a bug where keys could be automatically recreated if they had been manually added to Key Vault with all lowercase secret names
 - Update DotNetIsolatedNativeHost version to 1.0.3 (#9671)

src/WebJobs.Script.WebHost/Middleware/HostWarmupMiddleware.cs

@@ -53,7 +53,7 @@ public HostWarmupMiddleware(
 
         public Task Invoke(HttpContext httpContext)
         {
-            if (IsWarmUpRequest(httpContext.Request, _webHostEnvironment.InStandbyMode, _environment))
+            if (_webHostEnvironment.InStandbyMode)
             {
                 return WarmupInvoke(httpContext);
             }
@@ -167,6 +167,13 @@ public async Task HostWarmupAsync(HttpRequest request)
 
         public static bool IsWarmUpRequest(HttpRequest request, bool inStandbyMode, IEnvironment environment)
         {
+            // In placeholder simulation mode, we want the homepage request to also trigger warmup code.
+            var isWarmupViaHomePageRequest = Utility.IsInPlaceholderSimulationMode && inStandbyMode && request.Path.Value == "/";
+            if (isWarmupViaHomePageRequest)
+            {
+                return true;
+            }
+
             return inStandbyMode
                 && ((environment.IsAppService() && request.IsAppServiceInternalRequest(environment)) || environment.IsAnyLinuxConsumption())
                 && (request.Path.StartsWithSegments(_warmupRoutePath) || request.Path.StartsWithSegments(_warmupRouteAlternatePath));

src/WebJobs.Script/Utility.cs

@@ -44,6 +44,18 @@ public static class Utility
         private const string SasVersionQueryParam = "sv";
         private const string SasTokenExpirationDate = "se";
 
+        /// <summary>
+        /// Gets a value indicating whether the host is running in placeholder simulation mode.
+        /// This mode is used for testing placeholder scenarios locally.
+        /// Running using either "DebugPlaceholder" or "ReleasePlaceholder" configuration mode will
+        /// cause the host to run in placeholder simulation mode.
+        /// </summary>
+#if PLACEHOLDERSIMULATION
+        public const bool IsInPlaceholderSimulationMode = true;
+#else
+        public const bool IsInPlaceholderSimulationMode = false;
+#endif
+
         private static readonly Regex FunctionNameValidationRegex = new Regex(@"^[a-z][a-z0-9_\-]{0,127}$(?<!^host$)", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant);
         private static readonly Regex BindingNameValidationRegex = new Regex(string.Format("^([a-zA-Z][a-zA-Z0-9]{{0,127}}|{0})$", Regex.Escape(ScriptConstants.SystemReturnParameterBindingName)));
 
@@ -52,12 +64,6 @@ public static class Utility
 
         private static List<string> dotNetLanguages = new List<string>() { DotNetScriptTypes.CSharp, DotNetScriptTypes.DotNetAssembly };
 
-#if PLACEHOLDERSIMULATION
-        private static bool isInPlaceholderSimulationMode = true;
-#else
-        private static bool isInPlaceholderSimulationMode = false;
-#endif
-
         public static int ColdStartDelayMS { get; set; } = 5000;
 
         internal static bool TryGetHostService<TService>(IScriptHostManager scriptHostManager, out TService service) where TService : class
@@ -780,7 +786,7 @@ public static void ExecuteAfterDelay(Action targetAction, TimeSpan delay, Cancel
         public static void ExecuteAfterColdStartDelay(IEnvironment environment, Action targetAction, CancellationToken cancellationToken = default)
         {
             // for Dynamic SKUs where coldstart is important, we want to delay the action
-            if (isInPlaceholderSimulationMode || environment.IsDynamicSku())
+            if (IsInPlaceholderSimulationMode || environment.IsDynamicSku())
             {
                 ExecuteAfterDelay(targetAction, TimeSpan.FromMilliseconds(ColdStartDelayMS), cancellationToken);
             }