Serve 503 when PocketBase is unavailable across all content pages

Elternbeirat.Web/Features/Posts/PostDetail.razor

@@ -1,19 +1,25 @@
 @page "/posts/{Slug}"
 
-@if (_post is null)
+@if (_unavailable)
 {
-    <PageTitle>Nicht gefunden</PageTitle>
+    <PageTitle>Vorübergehend nicht erreichbar</PageTitle>
+    <p>Der Beitrag ist gerade nicht erreichbar. Bitte später erneut versuchen.</p>
 }
-else
+else if (_post is not null)
 {
     <PageTitle>@_post.Title</PageTitle>
+    <nav>
+        <a href="/posts">&larr; Alle Beiträge</a>
+    </nav>
     <article>
-        <p class="post-meta">
-            <a href="/posts">&larr; Alle Beiträge</a>
-            <time datetime="@_post.Date.ToString("yyyy-MM-dd")">
-                @_post.Date.ToString("d. MMMM yyyy", German)
+        <header>
+            <h1>@_post.Title</h1>
+            <time class="post-meta" datetime="@_post.Date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)">
+                @_post.Date.ToString("d. MMMM yyyy", Cultures.German)
             </time>
-        </p>
+        </header>
         @Body
     </article>
 }
+@* No post and not unavailable: the slug was unknown; NavigationManager.NotFound()
+   already ran in OnParametersSetAsync and renders the not-found page. *@

Elternbeirat.Web/Features/Posts/PostDetail.razor.cs

@@ -1,33 +1,42 @@
-using System.Globalization;
 using Elternbeirat.Contracts;
 using Elternbeirat.PocketBase;
 using Elternbeirat.Web.Shared;
 using Microsoft.AspNetCore.Components;
-using Microsoft.AspNetCore.Http;
 
 namespace Elternbeirat.Web.Features.Posts;
 
 public partial class PostDetail
 {
-    private static readonly CultureInfo German = CultureInfo.GetCultureInfo("de-DE");
-
-    [LoggerMessage(Level = LogLevel.Warning, Message = "Could not load post '{slug}' from PocketBase.")]
-    private static partial void LogLoadFailed(ILogger logger, string slug, Exception exception);
+    [LoggerMessage(
+        Level = LogLevel.Error,
+        Message = "Could not load post '{Slug}' from PocketBase; content source is unavailable.")]
+    private static partial void LogSourceUnavailable(
+        ILogger logger,
+        string slug,
+        Exception exception);
 
     [Parameter]
     public string Slug { get; set; } = string.Empty;
 
     [Inject]
-    private PocketBaseClient PocketBase { get; set; } = default!;
+    private PocketBaseClient PocketBase { get; set; } = null!;
 
     [Inject]
-    private ILogger<PostDetail> Logger { get; set; } = default!;
+    private ILogger<PostDetail> Logger { get; set; } = null!;
+
+    [Inject]
+    private NavigationManager Navigation { get; set; } = null!;
 
     [CascadingParameter]
     private HttpContext? HttpContext { get; set; }
 
     private Post? _post;
 
+    // Set when the content source could not be reached or read. The markup then
+    // shows a "temporarily unavailable" note instead of a not-found page, matching
+    // the 503 this sets on the response.
+    private bool _unavailable;
+
     // The post body rendered from Markdown to HTML, ready to emit as a
     // MarkupString in the markup.
     private MarkupString Body => (MarkupString)Markdown.ToHtml(_post?.Body);
@@ -36,24 +45,23 @@ public partial class PostDetail
     {
         try
         {
-            var posts = await PocketBase.GetPostsAsync();
+            var posts = await PocketBase.GetPostsAsync(HttpContext?.RequestAborted ?? CancellationToken.None);
             _post = posts.FirstOrDefault(
-                p => string.Equals(p.Slug, Slug, StringComparison.OrdinalIgnoreCase));
+                post => string.Equals(post.Slug, Slug, StringComparison.OrdinalIgnoreCase));
         }
-        catch (HttpRequestException ex)
+        catch (PocketBaseUnavailableException exception)
         {
-            // Source unreachable -> treat as "not found" rather than a 500. The
-            // 404 branch below serves the friendly /not-found page.
-            LogLoadFailed(Logger, Slug, ex);
-            _post = null;
+            // The site works, its data store is down: 503, not 404.
+            LogSourceUnavailable(Logger, Slug, exception);
+            _unavailable = true;
+            SourceUnavailable.SetStatus(HttpContext);
+            return;
         }
 
-        // Unknown slug (or unreachable source) -> 404, so
-        // UseStatusCodePagesWithReExecute serves the /not-found page instead of an
-        // empty 200 response.
-        if (_post is null && HttpContext is not null)
+        if (_post is null)
         {
-            HttpContext.Response.StatusCode = StatusCodes.Status404NotFound;
+            // The source answered, but there is no post with this slug: a genuine 404.
+            Navigation.NotFound();
         }
     }
 }

Elternbeirat.Web/Features/Posts/PostList.razor

@@ -4,7 +4,11 @@
 
 <h1>Beiträge</h1>
 
-@if (_posts.Count == 0)
+@if (_unavailable)
+{
+    <p>Die Beiträge sind gerade nicht erreichbar. Bitte später erneut versuchen.</p>
+}
+else if (_posts.Count == 0)
 {
     <p>Zurzeit gibt es keine Beiträge.</p>
 }
@@ -15,8 +19,8 @@ else
         {
             <li>
                 <a href="@($"/posts/{post.Slug}")">@post.Title</a>
-                <time datetime="@post.Date.ToString("yyyy-MM-dd")">
-                    @post.Date.ToString("d. MMMM yyyy", German)
+                <time datetime="@post.Date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)">
+                    @post.Date.ToString("d. MMMM yyyy", Cultures.German)
                 </time>
             </li>
         }

Elternbeirat.Web/Features/Posts/PostList.razor.cs

@@ -1,36 +1,48 @@
-using System.Globalization;
 using Elternbeirat.Contracts;
 using Elternbeirat.PocketBase;
+using Elternbeirat.Web.Shared;
 using Microsoft.AspNetCore.Components;
 
 namespace Elternbeirat.Web.Features.Posts;
 
 public partial class PostList
 {
-    [LoggerMessage(Level = LogLevel.Warning, Message = "Could not load posts from PocketBase.")]
-    private static partial void LogLoadFailed(ILogger logger, Exception exception);
-
-    private static readonly CultureInfo German = CultureInfo.GetCultureInfo("de-DE");
+    [LoggerMessage(
+        Level = LogLevel.Error,
+        Message = "Could not load posts from PocketBase; content source is unavailable.")]
+    private static partial void LogSourceUnavailable(
+        ILogger logger,
+        Exception exception);
 
     [Inject]
-    private PocketBaseClient PocketBase { get; set; } = default!;
+    private PocketBaseClient PocketBase { get; set; } = null!;
 
     [Inject]
-    private ILogger<PostList> Logger { get; set; } = default!;
+    private ILogger<PostList> Logger { get; set; } = null!;
+
+    [CascadingParameter]
+    private HttpContext? HttpContext { get; set; }
 
     private IReadOnlyList<Post> _posts = [];
 
+    // Set when the content source could not be reached or read. The markup then
+    // shows a "temporarily unavailable" note instead of "no posts", matching the
+    // 503 this sets on the response.
+    private bool _unavailable;
+
     protected override async Task OnInitializedAsync()
     {
         try
         {
-            _posts = await PocketBase.GetPostsAsync();
+            _posts = await PocketBase.GetPostsAsync(HttpContext?.RequestAborted ?? CancellationToken.None);
         }
-        catch (HttpRequestException ex)
+        catch (PocketBaseUnavailableException exception)
         {
-            // Source unreachable -> show an empty list instead of a 500. The page
-            // stays up; the "keine Beiträge" note is rendered.
-            LogLoadFailed(Logger, ex);
+            // An empty list would claim there are no posts. The site works, its
+            // data store is down: 503 and an honest note.
+            LogSourceUnavailable(Logger, exception);
+            _unavailable = true;
+            SourceUnavailable.SetStatus(HttpContext);
         }
     }
 }