[Blazor] Auto render mode improvements

src/Components/Web.JS/src/Boot.Web.ts

@@ -37,7 +37,6 @@ function boot(options?: Partial<WebStartOptions>) : Promise<void> {
   started = true;
   options = options || {};
   options.logLevel ??= LogLevel.Error;
-  Blazor._internal.loadWebAssemblyQuicklyTimeout = 3000;
 
   // Defined here to avoid inadvertently imported enhanced navigation
   // related APIs in WebAssembly or Blazor Server contexts.

src/Components/Web.JS/src/GlobalExports.ts

@@ -78,7 +78,6 @@ export interface IBlazor {
     receiveWebAssemblyDotNetDataStream?: (streamId: number, data: any, bytesRead: number, errorMessage: string) => void;
     receiveWebViewDotNetDataStream?: (streamId: number, data: any, bytesRead: number, errorMessage: string) => void;
     attachWebRendererInterop?: typeof attachWebRendererInterop;
-    loadWebAssemblyQuicklyTimeout?: number;
 
     // JSExport APIs
     dotNetExports?: {

src/Components/Web.JS/src/Services/WebRootComponentManager.ts

@@ -9,7 +9,6 @@ import { disposeCircuit, hasStartedServer, isCircuitAvailable, startCircuit, sta
 import { hasLoadedWebAssemblyPlatform, hasStartedLoadingWebAssemblyPlatform, hasStartedWebAssembly, isFirstUpdate, loadWebAssemblyPlatformIfNotStarted, resolveInitialUpdate, setWaitForRootComponents, startWebAssembly, updateWebAssemblyRootComponents, waitForBootConfigLoaded } from '../Boot.WebAssembly.Common';
 import { MonoConfig } from 'dotnet-runtime';
 import { RootComponentManager } from './RootComponentManager';
-import { Blazor } from '../GlobalExports';
 import { getRendererer } from '../Rendering/Renderer';
 import { isPageLoading } from './NavigationEnhancement';
 import { setShouldPreserveContentOnInteractiveComponentDisposal } from '../Rendering/BrowserRenderer';
@@ -100,12 +99,18 @@ export class WebRootComponentManager implements DescriptorHandler, RootComponent
       return;
     }
 
-    if (descriptor.type === 'auto' || descriptor.type === 'webassembly') {
-      // Eagerly start loading the WebAssembly runtime, even though we're not
-      // activating the component yet. This is becuase WebAssembly resources
-      // may take a long time to load, so starting to load them now potentially reduces
-      // the time to interactvity.
+    // When encountering a component with a WebAssembly or Auto render mode,
+    // start loading the WebAssembly runtime, even though we're not
+    // activating the component yet. This is becuase WebAssembly resources
+    // may take a long time to load, so starting to load them now potentially reduces
+    // the time to interactvity.
+    if (descriptor.type === 'webassembly') {
       this.startLoadingWebAssemblyIfNotStarted();
+    } else if (descriptor.type === 'auto') {
+      // If the WebAssembly runtime starts downloading because an Auto component was added to
+      // the page, we limit the maximum number of parallel WebAssembly resource downloads to 1
+      // so that the performance of any Blazor Server circuit is minimally impacted.
+      this.startLoadingWebAssemblyIfNotStarted(/* maxParallelDownloadsOverride */ 1);
     }
 
     const ssrComponentId = this._nextSsrComponentId++;
@@ -120,26 +125,20 @@ export class WebRootComponentManager implements DescriptorHandler, RootComponent
     this.circuitMayHaveNoRootComponents();
   }
 
-  private async startLoadingWebAssemblyIfNotStarted() {
+  private async startLoadingWebAssemblyIfNotStarted(maxParallelDownloadsOverride?: number) {
     if (hasStartedLoadingWebAssemblyPlatform()) {
       return;
     }
 
     setWaitForRootComponents();
 
     const loadWebAssemblyPromise = loadWebAssemblyPlatformIfNotStarted();
-
-    // If WebAssembly resources can't be loaded within some time limit,
-    // we take note of this fact so that "auto" components fall back
-    // to using Blazor Server.
-    setTimeout(() => {
-      if (!hasLoadedWebAssemblyPlatform()) {
-        this.onWebAssemblyFailedToLoadQuickly();
-      }
-    }, Blazor._internal.loadWebAssemblyQuicklyTimeout);
-
     const bootConfig = await waitForBootConfigLoaded();
 
+    if (maxParallelDownloadsOverride !== undefined) {
+      bootConfig.maxParallelDownloads = maxParallelDownloadsOverride;
+    }
+
     if (!areWebAssemblyResourcesLikelyCached(bootConfig)) {
       // Since WebAssembly resources aren't likely cached,
       // they will probably need to be fetched over the network.
@@ -299,6 +298,8 @@ export class WebRootComponentManager implements DescriptorHandler, RootComponent
         this.updateWebAssemblyRootComponents(batchJson);
       }
     }
+
+    this.circuitMayHaveNoRootComponents();
   }
 
   private updateWebAssemblyRootComponents(operationsJson: string) {

src/Components/test/E2ETest/ServerRenderingTests/InteractivityTest.cs

@@ -597,22 +597,6 @@ public void DynamicallyAddedSsrComponents_CanGetRemoved_BeforeStreamingRendering
         AssertBrowserLogDoesNotContainErrors();
     }
 
-    [Fact]
-    public void AutoRenderMode_UsesBlazorServer_IfWebAssemblyResourcesTakeTooLongToLoad()
-    {
-        Navigate(ServerPathBase);
-        Browser.Equal("Hello", () => Browser.Exists(By.TagName("h1")).Text);
-        ForceWebAssemblyResourceCacheMiss();
-        BlockWebAssemblyResourceLoad();
-
-        Navigate($"{ServerPathBase}/streaming-interactivity");
-        Browser.Equal("Not streaming", () => Browser.FindElement(By.Id("status")).Text);
-
-        Browser.Click(By.Id(AddAutoPrerenderedId));
-        Browser.Equal("True", () => Browser.FindElement(By.Id("is-interactive-0")).Text);
-        Browser.Equal("Server", () => Browser.FindElement(By.Id("render-mode-0")).Text);
-    }
-
     [Fact]
     public void AutoRenderMode_UsesBlazorWebAssembly_AfterAddingWebAssemblyRootComponent()
     {
@@ -659,8 +643,6 @@ public void AutoRenderMode_UsesBlazorServerOnFirstLoad_ThenWebAssemblyOnSuccessi
         Navigate(ServerPathBase);
         Browser.Equal("Hello", () => Browser.Exists(By.TagName("h1")).Text);
         BlockWebAssemblyResourceLoad();
-        UseLongWebAssemblyLoadTimeout();
-        ForceWebAssemblyResourceCacheMiss();
 
         Navigate($"{ServerPathBase}/streaming-interactivity");
         Browser.Equal("Not streaming", () => Browser.FindElement(By.Id("status")).Text);
@@ -697,8 +679,6 @@ public void AutoRenderMode_UsesBlazorServer_IfBootResourceHashChanges()
         Navigate(ServerPathBase);
         Browser.Equal("Hello", () => Browser.Exists(By.TagName("h1")).Text);
         BlockWebAssemblyResourceLoad();
-        UseLongWebAssemblyLoadTimeout();
-        ForceWebAssemblyResourceCacheMiss();
 
         Navigate($"{ServerPathBase}/streaming-interactivity");
         Browser.Equal("Not streaming", () => Browser.FindElement(By.Id("status")).Text);
@@ -715,14 +695,11 @@ public void AutoRenderMode_UsesBlazorServer_IfBootResourceHashChanges()
         Browser.Click(By.Id($"remove-counter-link-1"));
         Browser.DoesNotExist(By.Id("is-interactive-1"));
 
-        UseLongWebAssemblyLoadTimeout();
         Browser.Navigate().Refresh();
 
         Browser.Equal("True", () => Browser.FindElement(By.Id("is-interactive-0")).Text);
         Browser.Equal("WebAssembly", () => Browser.FindElement(By.Id("render-mode-0")).Text);
 
-        BlockWebAssemblyResourceLoad();
-        UseLongWebAssemblyLoadTimeout();
         ForceWebAssemblyResourceCacheMiss("dummy hash");
         Browser.Navigate().Refresh();
 
@@ -766,8 +743,6 @@ public void AutoRenderMode_CanUseBlazorServer_WhenMultipleAutoComponentsAreAdded
         Navigate(ServerPathBase);
         Browser.Equal("Hello", () => Browser.Exists(By.TagName("h1")).Text);
         BlockWebAssemblyResourceLoad();
-        UseLongWebAssemblyLoadTimeout();
-        ForceWebAssemblyResourceCacheMiss();
 
         Navigate($"{ServerPathBase}/streaming-interactivity");
         Browser.Equal("Not streaming", () => Browser.FindElement(By.Id("status")).Text);
@@ -911,6 +886,36 @@ public void AutoRenderMode_UsesBlazorServer_AfterWebAssemblyComponentsNoLongerEx
         Browser.Equal("Server", () => Browser.FindElement(By.Id("render-mode-3")).Text);
     }
 
+    [Fact]
+    public void WebAssemblyRenderMode_DownloadsWebAssemblyResourcesInParallel()
+    {
+        Navigate($"{ServerPathBase}/streaming-interactivity?ClearSiteData=True");
+        Browser.Equal("Not streaming", () => Browser.FindElement(By.Id("status")).Text);
+
+        Browser.Click(By.Id(AddWebAssemblyPrerenderedId));
+        Browser.Equal("True", () => Browser.FindElement(By.Id("is-interactive-0")).Text);
+        Browser.Equal("WebAssembly", () => Browser.FindElement(By.Id("render-mode-0")).Text);
+
+        Browser.True(() => GetMaxParallelWebAssemblyResourceDownloadCount() > 1);
+    }
+
+    [Fact]
+    public void AutoRenderMode_DoesNotDownloadWebAssemblyResourcesInParallel()
+    {
+        Navigate($"{ServerPathBase}/streaming-interactivity?ClearSiteData=True");
+        Browser.Equal("Not streaming", () => Browser.FindElement(By.Id("status")).Text);
+
+        Browser.Click(By.Id(AddAutoPrerenderedId));
+        Browser.Equal("True", () => Browser.FindElement(By.Id("is-interactive-0")).Text);
+        Browser.Equal("Server", () => Browser.FindElement(By.Id("render-mode-0")).Text);
+
+        Browser.Click(By.Id(AddWebAssemblyPrerenderedId));
+        Browser.Equal("True", () => Browser.FindElement(By.Id("is-interactive-1")).Text);
+        Browser.Equal("WebAssembly", () => Browser.FindElement(By.Id("render-mode-1")).Text);
+
+        Browser.Equal(1, GetMaxParallelWebAssemblyResourceDownloadCount);
+    }
+
     [Fact]
     public void Circuit_ShutsDown_WhenAllBlazorServerComponentsGetRemoved()
     {
@@ -1135,6 +1140,9 @@ public void NavigationManagerCanRefreshSSRPageWhenServerInteractivityEnabled()
 
     private void BlockWebAssemblyResourceLoad()
     {
+        // Force a WebAssembly resource cache miss so that we can fall back to using server interactivity
+        ForceWebAssemblyResourceCacheMiss();
+
         ((IJavaScriptExecutor)Browser).ExecuteScript("sessionStorage.setItem('block-load-boot-resource', 'true')");
 
         // Clear caches so that we can block the resource load
@@ -1146,11 +1154,6 @@ private void UnblockWebAssemblyResourceLoad()
         ((IJavaScriptExecutor)Browser).ExecuteScript("window.unblockLoadBootResource()");
     }
 
-    private void UseLongWebAssemblyLoadTimeout()
-    {
-        ((IJavaScriptExecutor)Browser).ExecuteScript("sessionStorage.setItem('use-long-auto-timeout', 'true')");
-    }
-
     private void ForceWebAssemblyResourceCacheMiss(string resourceHash = null)
     {
         if (resourceHash is not null)
@@ -1164,6 +1167,11 @@ private void ForceWebAssemblyResourceCacheMiss(string resourceHash = null)
         }
     }
 
+    private long GetMaxParallelWebAssemblyResourceDownloadCount()
+    {
+        return (long)((IJavaScriptExecutor)Browser).ExecuteScript("return window['__aspnetcore__testing__max__parallel__resource__download__count'] || 0;");
+    }
+
     private string InteractiveCallsiteUrl(bool prerender, int? serverIncrement = default, int? webAssemblyIncrement = default)
     {
         var result = $"{ServerPathBase}/interactive-callsite?suppress-autostart&prerender={prerender}";

src/Components/test/E2ETest/Tests/StatePersistenceTest.cs

@@ -31,7 +31,7 @@ public StatePersistenceTest(
     public override Task InitializeAsync()
         => InitializeAsync(BrowserFixture.StreamingContext + _nextStreamingIdContext++);
 
-    // Validates that we can use persisted state across server, webasembly, and auto modes, with and without
+    // Validates that we can use persisted state across server, webassembly, and auto modes, with and without
     // streaming rendering.
     // For streaming rendering, we validate that the state is captured and restored after streaming completes.
     // For enhanced navigation we validate that the state is captured at the time components are rendered for
@@ -101,6 +101,12 @@ public void CanRenderComponentWithPersistedState(bool suppressEnhancedNavigation
             RenderComponentsWithPersistentStateAndValidate(suppressEnhancedNavigation, mode, renderMode, streaming, interactiveRuntime: "server");
 
             UnblockWebAssemblyResourceLoad();
+
+            if (suppressEnhancedNavigation)
+            {
+                RenderWebAssemblyComponentAndWaitForWebAssemblyRuntime(returnUrl: Browser.Url);
+            }
+
             Browser.Navigate().Refresh();
 
             RenderComponentsWithPersistentStateAndValidate(suppressEnhancedNavigation, mode, renderMode, streaming, interactiveRuntime: "wasm");
@@ -123,16 +129,19 @@ public async Task StateIsProvidedEveryTimeACircuitGetsCreated(string streaming)
         }
         Browser.Click(By.Id("page-with-components-link"));
 
-        RenderComponentsWithPersistentStateAndValidate(suppresEnhancedNavigation: false, mode, typeof(InteractiveServerRenderMode), streaming);
+        RenderComponentsWithPersistentStateAndValidate(suppressEnhancedNavigation: false, mode, typeof(InteractiveServerRenderMode), streaming);
         Browser.Click(By.Id("page-no-components-link"));
         // Ensure that the circuit is gone.
         await Task.Delay(1000);
         Browser.Click(By.Id("page-with-components-link-and-state"));
-        RenderComponentsWithPersistentStateAndValidate(suppresEnhancedNavigation: false, mode, typeof(InteractiveServerRenderMode), streaming, stateValue: "other");
+        RenderComponentsWithPersistentStateAndValidate(suppressEnhancedNavigation: false, mode, typeof(InteractiveServerRenderMode), streaming, stateValue: "other");
     }
 
     private void BlockWebAssemblyResourceLoad()
     {
+        // Clear local storage so that the resource hash is not found
+        ((IJavaScriptExecutor)Browser).ExecuteScript("localStorage.clear()");
+
         ((IJavaScriptExecutor)Browser).ExecuteScript("sessionStorage.setItem('block-load-boot-resource', 'true')");
 
         // Clear caches so that we can block the resource load
@@ -145,7 +154,7 @@ private void UnblockWebAssemblyResourceLoad()
     }
 
     private void RenderComponentsWithPersistentStateAndValidate(
-        bool suppresEnhancedNavigation,
+        bool suppressEnhancedNavigation,
         string mode,
         Type renderMode,
         string streaming,
@@ -154,7 +163,7 @@ private void RenderComponentsWithPersistentStateAndValidate(
     {
         stateValue ??= "restored";
         // No need to navigate if we are using enhanced navigation, the tests will have already navigated to the page via a link.
-        if (suppresEnhancedNavigation)
+        if (suppressEnhancedNavigation)
         {
             // In this case we suppress auto start to check some server side state before we boot Blazor.
             if (streaming == null)
@@ -232,6 +241,18 @@ private void AssertPageState(
         }
     }
 
+    private void RenderWebAssemblyComponentAndWaitForWebAssemblyRuntime(string returnUrl = null)
+    {
+        Navigate("subdir/persistent-state/page-with-webassembly-interactivity");
+
+        Browser.Equal("True", () => Browser.FindElement(By.Id("is-interactive-counter")).Text);
+
+        if (returnUrl is not null)
+        {
+            Navigate(returnUrl);
+        }
+    }
+
     private void SuppressEnhancedNavigation(bool shouldSuppress)
         => EnhancedNavigationTestUtil.SuppressEnhancedNavigation(this, shouldSuppress);
 }

src/Components/test/testassets/Components.TestServer/RazorComponents/App.razor

@@ -21,10 +21,8 @@
         const enableClassicInitializers = sessionStorage.getItem('enable-classic-initializers') === 'true';
         const suppressEnhancedNavigation = sessionStorage.getItem('suppress-enhanced-navigation') === 'true';
         const blockLoadBootResource = sessionStorage.getItem('block-load-boot-resource') === 'true';
-        const useLongWebAssemblyTimeout = sessionStorage.getItem('use-long-auto-timeout') === 'true';
         sessionStorage.removeItem('suppress-enhanced-navigation');
         sessionStorage.removeItem('block-load-boot-resource');
-        sessionStorage.removeItem('use-long-auto-timeout');
         sessionStorage.removeItem('enable-classic-initializers');
 
         let loadBootResourceUnblocked = null;
@@ -34,6 +32,9 @@
             });
         }
 
+        let maxParallelResourceDownloadCount = 0;
+        let currentParallelResourceDownloadCount = 0;
+
         function callBlazorStart() {
             Blazor.start({
                 ssr: {
@@ -55,19 +56,21 @@
                                 // The following allows us to arbitrarily delay the loading of WebAssembly resources.
                                 // This is useful for guaranteeing that auto mode components will fall back on
                                 // using Blazor server.
+                                currentParallelResourceDownloadCount++;
                                 return fetch(`${document.baseURI}WasmMinimal/_framework/${name}?`, {
                                     method: "GET",
                                 }).then(async (response) => {
+                                    if (currentParallelResourceDownloadCount > maxParallelResourceDownloadCount) {
+                                        maxParallelResourceDownloadCount = currentParallelResourceDownloadCount;
+                                        window['__aspnetcore__testing__max__parallel__resource__download__count'] = maxParallelResourceDownloadCount;
+                                    }
+                                    currentParallelResourceDownloadCount--;
                                     await loadBootResourceUnblocked;
                                     return response;
                                 });
                         }
                     },
                 },
-            }).then(() => {
-                if (useLongWebAssemblyTimeout) {
-                    Blazor._internal.loadWebAssemblyQuicklyTimeout = 10000000;
-                }
             }).then(() => {
                 const startedParagraph = document.createElement('p');
                 startedParagraph.id = 'blazor-started';

src/Components/test/testassets/Components.TestServer/RazorComponents/Components/InteractiveStreamingRenderingComponent.razor

@@ -100,6 +100,9 @@ else
     ComponentState _state = new(ImmutableArray<CounterInfo>.Empty, NextCounterId: 0);
     bool _isStreaming = false;
 
+    [CascadingParameter]
+    public HttpContext HttpContext { get; set; }
+
     [SupplyParameterFromQuery]
     public string? InitialState { get; set; }
 
@@ -109,13 +112,21 @@ else
     [SupplyParameterFromQuery]
     public bool DisableKeys { get; set; }
 
+    [SupplyParameterFromQuery]
+    public bool ClearSiteData { get; set; }
+
     protected override async Task OnInitializedAsync()
     {
         if (InitialState is not null)
         {
             _state = ReadStateFromJson(InitialState);
         }
 
+        if (ClearSiteData)
+        {
+            HttpContext.Response.Headers["Clear-Site-Data"] = "\"*\"";
+        }
+
         if (ShouldStream)
         {
             _isStreaming = true;

src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/PageWithWebAssemblyInteractivity.razor

@@ -0,0 +1,8 @@
+@page "/persistent-state/page-with-webassembly-interactivity"
+
+<p>
+    This page is used to ensure that the WebAssembly runtime is downloaded and available
+    so that WebAssembly interactivity will get used for components with the Auto render mode
+</p>
+
+<TestContentPackage.Counter @rendermode="RenderMode.InteractiveWebAssembly" IncrementAmount="1" IdSuffix="counter" />