Improve Boilerplate response caching (#9782)

src/Templates/Boilerplate/Bit.Boilerplate/src/Server/Boilerplate.Server.Api/Services/AppResponseCachePolicy.cs

@@ -4,8 +4,15 @@
 
 namespace Boilerplate.Server.Api.Services;
 
+/// <summary>
+/// An implementation of this interface can update how the current request is cached.
+/// </summary>
 public class AppResponseCachePolicy(IHostEnvironment env) : IOutputCachePolicy
 {
+    /// <summary>
+    /// Updates the <see cref="OutputCacheContext"/> before the cache middleware is invoked.
+    /// At that point the cache middleware can still be enabled or disabled for the request.
+    /// </summary>
     public async ValueTask CacheRequestAsync(OutputCacheContext context, CancellationToken cancellation)
     {
         var responseCacheAtt = context.HttpContext.GetResponseCacheAttribute();
@@ -35,6 +42,7 @@ public async ValueTask CacheRequestAsync(OutputCacheContext context, Cancellatio
         if (env.IsDevelopment())
         {
             // To enhance the developer experience, return from here to make it easier for developers to debug cacheable responses.
+            edgeCacheTtl = -1;
             outputCacheTtl = -1;
             browserCacheTtl = -1;
         }
@@ -76,22 +84,33 @@ public async ValueTask CacheRequestAsync(OutputCacheContext context, Cancellatio
         }
 
         // ASP.NET Core Output Cache
-        if (outputCacheTtl != -1)
+        if (outputCacheTtl > 0)
         {
             context.Tags.Add(requestUrl);
             context.AllowCacheLookup = true;
             context.AllowCacheStorage = true;
             context.ResponseExpirationTimeSpan = TimeSpan.FromSeconds(outputCacheTtl);
         }
 
+        //#if (api == "Integrated")
+        context.HttpContext.Items["AppResponseCachePolicy__DisableStreamPrerendering"] = outputCacheTtl > 0 || edgeCacheTtl > 0;
+        //#endif
         context.HttpContext.Response.Headers.TryAdd("App-Cache-Response", FormattableString.Invariant($"Output:{outputCacheTtl},Edge:{edgeCacheTtl},Browser:{browserCacheTtl}"));
     }
 
+    /// <summary>
+    /// Updates the <see cref="OutputCacheContext"/> before the cached response is used.
+    /// At that point the freshness of the cached response can be updated.
+    /// </summary>
     public async ValueTask ServeFromCacheAsync(OutputCacheContext context, CancellationToken cancellation)
     {
 
     }
 
+    /// <summary>
+    /// Updates the <see cref="OutputCacheContext"/> before the response is served and can be cached.
+    /// At that point cacheability of the response can be updated.
+    /// </summary>
     public async ValueTask ServeResponseAsync(OutputCacheContext context, CancellationToken cancellation)
     {
         var response = context.HttpContext.Response;

src/Templates/Boilerplate/Bit.Boilerplate/src/Server/Boilerplate.Server.Web/Components/App.razor

@@ -65,7 +65,7 @@
         <LoadingComponent @rendermode="null" />
     }
 
-    @if (HttpContext.Request.IsCrawlerClient())
+    @if (HttpContext.Request.DisableStreamPrerendering())
     {
         // For StreamRenderingDisabledContainer, read comments in App.razor.cs
         <StreamRenderingDisabledContainer>

src/Templates/Boilerplate/Bit.Boilerplate/src/Server/Boilerplate.Server.Web/Extensions/HttpRequestExtensions.cs

@@ -28,6 +28,14 @@ public static Uri GetUri(this HttpRequest request)
         return new Uri($"{request.Scheme}://{((!request.Host.HasValue) ? "UNKNOWN-HOST" : ((request.Host.Value.IndexOf(',') > 0) ? "MULTIPLE-HOST" : request.Host.Value))}{(request.PathBase.HasValue ? request.PathBase.Value : string.Empty)}{(request.Path.HasValue ? request.Path.Value : string.Empty)}{(request.QueryString.HasValue ? request.QueryString.Value : string.Empty)}");
     }
 
+    public static bool DisableStreamPrerendering(this HttpRequest request)
+    {
+        if (request.HttpContext.Items.TryGetValue("AppResponseCachePolicy__DisableStreamPrerendering", out var val) && val is true)
+            return true;  // The response from streaming pre-rendering is not suitable for caching in ASP.NET Core's output caching mechanism or on CDN edge servers.
+
+        return request.IsCrawlerClient();
+    }
+
     public static bool IsCrawlerClient(this HttpRequest request)
     {
         var agent = GetLoweredUserAgent(request);

src/Templates/Boilerplate/Bit.Boilerplate/src/Server/Boilerplate.Server.Web/Program.Middlewares.cs

@@ -202,6 +202,8 @@ private static void UseSiteMap(this WebApplication app)
 
             var baseUrl = context.Request.GetBaseUrl();
 
+            context.Response.Headers.ContentType = "application/xml";
+
             await context.Response.WriteAsync(string.Format(SITEMAP_INDEX_FORMAT, baseUrl), context.RequestAborted);
         }).CacheOutput("AppResponseCachePolicy").WithTags("Sitemaps");
 

src/Templates/Boilerplate/Bit.Boilerplate/src/Server/Boilerplate.Server.Web/Services/AppResponseCachePolicy.cs

@@ -4,8 +4,15 @@
 
 namespace Boilerplate.Server.Web.Services;
 
+/// <summary>
+/// An implementation of this interface can update how the current request is cached.
+/// </summary>
 public class AppResponseCachePolicy(IHostEnvironment env) : IOutputCachePolicy
 {
+    /// <summary>
+    /// Updates the <see cref="OutputCacheContext"/> before the cache middleware is invoked.
+    /// At that point the cache middleware can still be enabled or disabled for the request.
+    /// </summary>
     public async ValueTask CacheRequestAsync(OutputCacheContext context, CancellationToken cancellation)
     {
         var responseCacheAtt = context.HttpContext.GetResponseCacheAttribute();
@@ -35,6 +42,7 @@ public async ValueTask CacheRequestAsync(OutputCacheContext context, Cancellatio
         if (env.IsDevelopment())
         {
             // To enhance the developer experience, return from here to make it easier for developers to debug cacheable responses.
+            edgeCacheTtl = -1;
             outputCacheTtl = -1;
             browserCacheTtl = -1;
         }
@@ -74,22 +82,31 @@ public async ValueTask CacheRequestAsync(OutputCacheContext context, Cancellatio
         }
 
         // ASP.NET Core Output Cache
-        if (outputCacheTtl != -1)
+        if (outputCacheTtl > 0)
         {
             context.Tags.Add(requestUrl);
             context.AllowCacheLookup = true;
             context.AllowCacheStorage = true;
             context.ResponseExpirationTimeSpan = TimeSpan.FromSeconds(outputCacheTtl);
         }
 
+        context.HttpContext.Items["AppResponseCachePolicy__DisableStreamPrerendering"] = outputCacheTtl > 0 || edgeCacheTtl > 0;
         context.HttpContext.Response.Headers.TryAdd("App-Cache-Response", FormattableString.Invariant($"Output:{outputCacheTtl},Edge:{edgeCacheTtl},Browser:{browserCacheTtl}"));
     }
 
+    /// <summary>
+    /// Updates the <see cref="OutputCacheContext"/> before the cached response is used.
+    /// At that point the freshness of the cached response can be updated.
+    /// </summary>
     public async ValueTask ServeFromCacheAsync(OutputCacheContext context, CancellationToken cancellation)
     {
 
     }
 
+    /// <summary>
+    /// Updates the <see cref="OutputCacheContext"/> before the response is served and can be cached.
+    /// At that point cacheability of the response can be updated.
+    /// </summary>
     public async ValueTask ServeResponseAsync(OutputCacheContext context, CancellationToken cancellation)
     {
         var response = context.HttpContext.Response;