gaepdit · dougwaldron · Jul 30, 2026 · Jul 30, 2026 · Jul 30, 2026 · Jul 30, 2026
diff --git a/src/WebApp/Pages/Error.cshtml b/src/WebApp/Pages/Error.cshtml
@@ -4,12 +4,5 @@
     ViewData["Title"] = "Error";
 }
 
-<h1 class="text-danger">Error.</h1>
-<h2 class="text-danger">An error occurred while processing your request.</h2>
-
-@if (Model.ShowRequestId)
-{
-    <p>
-        <strong>Request ID:</strong> <code>@Model.RequestId</code>
-    </p>
-}
+<h1 class="text-danger-emphasis">@ViewData["Title"]</h1>
+<p class="lead">An error occurred while processing your request.</p>
diff --git a/src/WebApp/Pages/Error.cshtml.cs b/src/WebApp/Pages/Error.cshtml.cs
@@ -1,14 +1,7 @@
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.RazorPages;
-using System.Diagnostics;
 
 namespace WebApp.Pages;
 
 [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
-[IgnoreAntiforgeryToken]
-public class ErrorModel : PageModel
-{
-    public string? RequestId { get; set; }
-    public bool ShowRequestId => !string.IsNullOrEmpty(RequestId);
-    public void OnGet() => RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier;
-}
+public class ErrorModel : PageModel;
diff --git a/src/WebApp/Pages/Index.cshtml b/src/WebApp/Pages/Index.cshtml
@@ -122,13 +122,9 @@
 <div class="mt-4">
     <small class="text-body-secondary">
         <a href="https://github.com/gaepdit/server-checkup" target="_blank" rel="noopener">Server Checkup</a>
-        @if (Model.Version is not null)
+        @if (!string.IsNullOrEmpty(AppSettings.Version))
         {
-            @: | Version @Model.Version
-        }
-        @if (Model.Build is not null)
-        {
-            @: <em>(@Model.Build)</em>
+            @:| Version: <em>@AppSettings.Version</em>
         }
     </small>
 </div>

diff --git a/src/WebApp/Pages/Index.cshtml.cs b/src/WebApp/Pages/Index.cshtml.cs
@@ -1,7 +1,6 @@
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.RazorPages;
 using ServerCheckupLibrary;
-using System.Reflection;
 using WebApp.Platform;
 
 namespace WebApp.Pages;
@@ -14,9 +13,6 @@ public class IndexModel : PageModel
     public ResultMessage? ExternalServiceCheckMessage { get; private set; }
     public ResultMessage? DotnetVersionCheckMessage { get; private set; }
 
-    public string? Version { get; private set; }
-    public string? Build { get; private set; }
-
     public IActionResult OnGet()
     {
         if (User.Identity is not { IsAuthenticated: true })
@@ -47,14 +43,6 @@ public IActionResult OnGet()
             DotnetVersionCheckMessage = new ResultMessage(Context.Info, ".NET version checks are disabled.");
         }
 
-        // Get app version.
-        var entryAssembly = Assembly.GetEntryAssembly();
-        var segments = (entryAssembly?.GetCustomAttribute<AssemblyInformationalVersionAttribute>()?
-            .InformationalVersion ?? entryAssembly?.GetName().Version?.ToString() ?? "").Split('+');
-
-        Version = segments[0];
-        if (segments.Length > 0) Build = segments[1][..Math.Min(7, segments[1].Length)];
-
         return Page();
     }
 }
diff --git a/src/WebApp/Pages/Shared/_Layout.cshtml b/src/WebApp/Pages/Shared/_Layout.cshtml
@@ -7,6 +7,7 @@
     <link rel="icon" href="@Url.Content("~/icon.svg")" type="image/svg+xml">
     <link rel="stylesheet" href="~/lib/bootstrap/dist/css/bootstrap.min.css" />
     <link rel="stylesheet" href="~/css/site.css" />
+    <partial name="Shared/_MonitoringScriptsPartial" />
 </head>
 <body>
 <div class="container pt-3">

diff --git a/src/WebApp/Pages/Shared/_MonitoringScriptsPartial.cshtml b/src/WebApp/Pages/Shared/_MonitoringScriptsPartial.cshtml
@@ -0,0 +1,39 @@
+@using WebApp.Platform
+@{
+    // DataDog
+    var ddClientToken = AppSettings.DataDogSettings.ClientToken;
+    var ddApplicationId = AppSettings.DataDogSettings.ApplicationId;
+    const string service = "checkup";
+
+    if (!string.IsNullOrEmpty(ddClientToken) && !string.IsNullOrEmpty(ddApplicationId))
+    {
+        <script asp-add-nonce>
+            @* @formatter:off *@
+            (function(h,o,u,n,d) {
+                h=h[d]=h[d]||{q:[],onReady:function(c){h.q.push(c)}}
+                d=o.createElement(u);d.async=1;d.src=n;d.crossOrigin=''
+                n=o.getElementsByTagName(u)[0];n.parentNode.insertBefore(d,n)
+            })(window,document,'script','https://www.datadoghq-browser-agent.com/us3/v7/datadog-rum.js','DD_RUM');
+            @* @formatter:on  *@
+
+            window.DD_RUM.onReady(function () {
+                window.DD_RUM.init({
+                    clientToken: '@ddClientToken',
+                    applicationId: '@ddApplicationId',
+                    site: 'us3.datadoghq.com',
+                    service: '@service',
+                    env: '@AppSettings.ShortEnv',
+                    version: '@AppSettings.SimpleVersion',
+                    forwardErrorsToLogs: true,
+                    forwardConsoleLogs: ['error', 'warn'],
+                    sessionSampleRate: 100,
+                    sessionReplaySampleRate: 20,
+                    beforeSend: (log) => {
+                        // discard debug logs
+                        if (log.level === 'debug') return false;
+                    },
+                });
+            })
+        </script>
+    }
+}
diff --git a/src/WebApp/Platform/AppSettings.cs b/src/WebApp/Platform/AppSettings.cs
@@ -1,9 +1,10 @@
 using JetBrains.Annotations;
 using ServerCheckupLibrary.Checks;
+using System.Reflection;
 
 namespace WebApp.Platform;
 
-public static class AppSettings
+internal static class AppSettings
 {
     public static CheckEmailOptions CheckEmailOptions { get; } = new();
     public static CheckDatabaseOptions CheckDatabaseOptions { get; } = new();
@@ -12,6 +13,45 @@ public static class AppSettings
     public static CheckDotnetVersionOptions CheckDotnetVersionOptions { get; } = new();
     public static string ServerName { get; set; } = string.Empty;
     public static DevOptions DevOptions { get; } = new();
+
+    public static string? Version { get; private set; }
+    public static string? SimpleVersion => Version?.Split('+')[0];
+
+    private static string Env { get; } = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") ?? "unknown";
+    public static string ShortEnv => Env switch { "Production" => "prod", "Staging" => "uat", _ => "dev" };
+    public static DataDog DataDogSettings { get; } = new();
+
+    public record DataDog
+    {
+        public string? ClientToken { get; [UsedImplicitly] init; }
+        public string? ApplicationId { get; [UsedImplicitly] init; }
+    }
+
+    public static void BindAppSettings(this IHostApplicationBuilder builder)
+    {
+        // Set default timeout for regular expressions.
+        // https://learn.microsoft.com/en-us/dotnet/standard/base-types/best-practices#use-time-out-values
+        AppDomain.CurrentDomain.SetData("REGEX_DEFAULT_MATCH_TIMEOUT", TimeSpan.FromMilliseconds(100));
+
+        Version = GetVersion();
+        ServerName = builder.Configuration.GetValue<string>(nameof(ServerName)) ?? "Unknown";
+
+        builder.Configuration.GetSection(nameof(CheckEmailOptions)).Bind(CheckEmailOptions);
+        builder.Configuration.GetSection(nameof(CheckDatabaseOptions)).Bind(CheckDatabaseOptions);
+        builder.Configuration.GetSection(nameof(CheckDatabaseEmailOptions)).Bind(CheckDatabaseEmailOptions);
+        builder.Configuration.GetSection(nameof(CheckExternalServiceOptions)).Bind(CheckExternalServiceOptions);
+        builder.Configuration.GetSection(nameof(CheckDotnetVersionOptions)).Bind(CheckDotnetVersionOptions);
+        builder.Configuration.GetSection(nameof(DevOptions)).Bind(DevOptions);
+        builder.Configuration.GetSection(nameof(DataDogSettings)).Bind(DataDogSettings);
+    }
+
+    private static string GetVersion()
+    {
+        var entryAssembly = Assembly.GetEntryAssembly();
+        var segments = (entryAssembly?.GetCustomAttribute<AssemblyInformationalVersionAttribute>()?
+            .InformationalVersion ?? entryAssembly?.GetName().Version?.ToString() ?? "").Split('+');
+        return segments[0] + (segments.Length > 0 ? $"+{segments[1][..Math.Min(7, segments[1].Length)]}" : "");
+    }
 }
 
 [UsedImplicitly(ImplicitUseTargetFlags.Members)]

diff --git a/src/WebApp/Platform/AuthenticationServices.cs b/src/WebApp/Platform/AuthenticationServices.cs
@@ -0,0 +1,48 @@
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Authentication.Cookies;
+using Microsoft.AspNetCore.Authentication.OpenIdConnect;
+using Microsoft.IdentityModel.Protocols.OpenIdConnect;
+using Microsoft.IdentityModel.Tokens;
+
+namespace WebApp.Platform;
+
+public static class AuthenticationServices
+{
+    public static void ConfigureAuthentication(this IHostApplicationBuilder builder)
+    {
+        if (AppSettings.DevOptions.UseLocalAuth)
+        {
+            // When running locally, use a built-in authenticated user.
+            builder.Services
+                .AddAuthentication(LocalAuthenticationHandler.BasicAuthenticationScheme)
+                .AddScheme<AuthenticationSchemeOptions, LocalAuthenticationHandler>(
+                    LocalAuthenticationHandler.BasicAuthenticationScheme, null);
+        }
+        else
+        {
+            // When running on the server, require an OIDC login provider (configured in the app settings file).
+            builder.Services
+                .AddAuthentication(options =>
+                {
+                    options.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
+                    options.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;
+                })
+                .AddCookie()
+                .AddOpenIdConnect(configureOptions: options =>
+                {
+                    var configSection = builder.Configuration.GetSection("OIDC");
+
+                    options.Authority = configSection["Authority"];
+                    options.ClientId = configSection["ClientId"];
+                    options.ClientSecret = configSection["ClientSecret"];
+                    options.CallbackPath = configSection["CallbackPath"];
+
+                    options.Scope.Add("email");
+                    options.SignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;
+                    options.ResponseType = OpenIdConnectResponseType.Code;
+                    options.MapInboundClaims = false;
+                    options.TokenValidationParameters = new TokenValidationParameters { NameClaimType = "email" };
+                });
+        }
+    }
+}
diff --git a/src/WebApp/Program.cs b/src/WebApp/Program.cs
@@ -1,67 +1,21 @@
-using Microsoft.AspNetCore.Authentication;
-using Microsoft.AspNetCore.Authentication.Cookies;
-using Microsoft.AspNetCore.Authentication.OpenIdConnect;
-using Microsoft.IdentityModel.Protocols.OpenIdConnect;
-using Microsoft.IdentityModel.Tokens;
-using ServerCheckupLibrary.Checks;
 using ServerCheckupLibrary.Hubs;
 using WebApp.Platform;
 using ZLogger;
 
 var builder = WebApplication.CreateBuilder(args);
 var isDevelopment = builder.Environment.IsDevelopment();
 
-// Configure logging
+// Configure logging.
 builder.Logging.ClearProviders().AddZLoggerConsole(options => options.UseJsonFormatter());
 
-// Persist data protection keys
+// Persist data protection keys.
 builder.Services.AddDataProtection();
 
 // Bind application settings.
-builder.Configuration.GetSection(nameof(CheckEmailOptions)).Bind(AppSettings.CheckEmailOptions);
-builder.Configuration.GetSection(nameof(CheckDatabaseOptions)).Bind(AppSettings.CheckDatabaseOptions);
-builder.Configuration.GetSection(nameof(CheckDatabaseEmailOptions)).Bind(AppSettings.CheckDatabaseEmailOptions);
-builder.Configuration.GetSection(nameof(CheckExternalServiceOptions)).Bind(AppSettings.CheckExternalServiceOptions);
-builder.Configuration.GetSection(nameof(CheckDotnetVersionOptions)).Bind(AppSettings.CheckDotnetVersionOptions);
-builder.Configuration.GetSection(nameof(DevOptions)).Bind(AppSettings.DevOptions);
-AppSettings.ServerName = builder.Configuration.GetValue<string>(nameof(AppSettings.ServerName)) ?? "Unknown";
-
-// Configure authentication.
-if (AppSettings.DevOptions.UseLocalAuth)
-{
-    // When running locally, use a built-in authenticated user.
-    builder.Services
-        .AddAuthentication(LocalAuthenticationHandler.BasicAuthenticationScheme)
-        .AddScheme<AuthenticationSchemeOptions, LocalAuthenticationHandler>(
-            LocalAuthenticationHandler.BasicAuthenticationScheme, null);
-}
-else
-{
-    // When running on the server, require an OIDC login provider (configured in the appsettings file).
-    builder.Services
-        .AddAuthentication(options =>
-        {
-            options.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
-            options.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;
-        })
-        .AddCookie()
-        .AddOpenIdConnect(configureOptions: options =>
-        {
-            var configSection = builder.Configuration.GetSection("OIDC");
-
-            options.Authority = configSection["Authority"];
-            options.ClientId = configSection["ClientId"];
-            options.ClientSecret = configSection["ClientSecret"];
-            options.CallbackPath = configSection["CallbackPath"];
-
-            options.Scope.Add("email");
-            options.SignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;
-            options.ResponseType = OpenIdConnectResponseType.Code;
-            options.MapInboundClaims = false;
-            options.TokenValidationParameters = new TokenValidationParameters { NameClaimType = "email" };
-        });
-}
+builder.BindAppSettings();
 
+// Configure authentication and authorization.
+builder.ConfigureAuthentication();
 builder.Services.AddAuthorization();
 
 // Add SignalR

diff --git a/src/WebApp/appsettings-example.json b/src/WebApp/appsettings-example.json
@@ -68,8 +68,12 @@
     "Instance": "https://login.microsoftonline.com/",
     "Domain": "qualified.domain.name",
     "TenantId": "00000000-0000-0000-0000-000000000000",
-    "ClientId": "00000000-0000-0000-00000000000000000",
+    "ClientId": "00000000-0000-0000-0000-000000000000",
     "CallbackPath": "/signin-oidc"
   },
+  "DataDogSettings": {
+    "ClientToken": "pub0000000000000000000",
+    "ApplicationId": "00000000-0000-0000-0000-000000000000"
+  },
   "AllowedHosts": "*"
 }
diff --git a/src/WebApp/appsettings.json b/src/WebApp/appsettings.json
@@ -32,6 +32,10 @@
     "ClientId": "",
     "CallbackPath": "/signin-oidc"
   },
+  "DataDogSettings": {
+    "ClientToken": "",
+    "ApplicationId": ""
+  },
   "Logging": {
     "LogLevel": {
       "Default": "Information",