Some peer feedback addressed

Author: IEvangelist

docs/core/diagnostics/diagnostic-libraries.md

@@ -1,7 +1,7 @@
 ---
 title: Diagnostic libraries
 description: An overview of the available diagnostic libraries in .NET.
-ms.date: 10/16/2023
+ms.date: 10/20/2023
 ms.topic: overview
 ---
 

docs/core/diagnostics/snippets/exception-summary/Program.cs

@@ -12,14 +12,17 @@
 // Get the exception summarizer.
 var summarizer = provider.GetRequiredService<IExceptionSummarizer>();
 
-foreach (var exception in new Exception[]
-    {
-        new OperationCanceledException("Operation cancelled..."),
-        new TaskCanceledException("Task cancelled..."),
-        new SocketException(10_024, "Too many sockets open..."),
-        new WebException("Keep alive failure...",
-            WebExceptionStatus.KeepAliveFailure)
-    })
+// Define exceptions to summarize.
+Exception[] exceptions =
+[
+    new OperationCanceledException("Operation cancelled..."),
+    new TaskCanceledException("Task cancelled..."),
+    new SocketException(10_024, "Too many sockets open..."),
+    new WebException("Keep alive failure...",
+        WebExceptionStatus.KeepAliveFailure)
+];
+
+foreach (var exception in exceptions)
 {
     // Summarize the exception.
     var summary = summarizer.Summarize(exception);
@@ -28,9 +31,3 @@
 }
 
 Console.ReadLine();
-
-// Sample output:
-//   OperationCanceledException:TaskTimeout:Unknown
-//   TaskCanceledException:TaskTimeout:Unknown
-//   SocketException:TooManyOpenSockets:Unknown
-//   WebException:KeepAliveFailure:Unknown

docs/core/diagnostics/snippets/lifetime-health-checks/ExampleLifecycle.cs

@@ -0,0 +1,41 @@
+using System.Runtime.CompilerServices;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+internal class ExampleLifecycle(
+    HealthCheckService healthCheckService,
+    ILogger<ExampleLifecycle> logger) : IHostedLifecycleService
+{
+    Task IHostedService.StartAsync(CancellationToken cancellationToken) =>
+        CheckHealthAsync(cancellationToken: cancellationToken);
+
+    Task IHostedLifecycleService.StartedAsync(CancellationToken cancellationToken) =>
+        CheckHealthAsync(cancellationToken: cancellationToken);
+
+    Task IHostedLifecycleService.StartingAsync(CancellationToken cancellationToken) =>
+        CheckHealthAsync(cancellationToken: cancellationToken);
+
+    Task IHostedService.StopAsync(CancellationToken cancellationToken) =>
+        CheckHealthAsync(cancellationToken: cancellationToken);
+
+    Task IHostedLifecycleService.StoppedAsync(CancellationToken cancellationToken) =>
+        CheckHealthAsync(cancellationToken: cancellationToken);
+
+    Task IHostedLifecycleService.StoppingAsync(CancellationToken cancellationToken) =>
+        CheckHealthAsync(cancellationToken: cancellationToken);
+
+    public Task PostStartedAndPreStoppingAsync() => CheckHealthAsync();
+
+    private async Task CheckHealthAsync(
+         [CallerMemberName] string eventName = "",
+         CancellationToken cancellationToken = default)
+    {
+        var result =
+            await healthCheckService.CheckHealthAsync(cancellationToken);
+
+        logger.LogInformation(
+            "{EventName}: {Status} {TotalDuration}",
+            eventName, result.Status, result.TotalDuration);
+    }
+}

docs/core/diagnostics/snippets/lifetime-health-checks/Program.cs

@@ -5,44 +5,22 @@
 var builder = Host.CreateApplicationBuilder(args);
 
 var healthChecksBuilder = builder.Services
+    .AddSingleton<ExampleLifecycle>()
+    .AddHostedService<ExampleLifecycle>()
     .AddHealthChecks()
     .AddApplicationLifecycleHealthCheck();
 
+// You could use the healthChecksBuilder instance to add more checks...
+
 var app = builder.Build();
 
-var lifetime = app.Services.GetRequiredService<IHostApplicationLifetime>();
-var healthCheckService = app.Services.GetRequiredService<HealthCheckService>();
+var example = app.Services.GetRequiredService<ExampleLifecycle>();
 
-void ReportHealthCheck(string eventName)
+async Task DelayAndRepostAsync()
 {
-    // ⚠️ Normally, you would await the result of CheckHealthAsync, but this
-    // function is called in a synchronous context, so we block instead...
-    var result = healthCheckService!.CheckHealthAsync().GetAwaiter().GetResult();
-
-    Console.WriteLine($"{eventName}: {result.Status} {result.TotalDuration}");
+    // Ensure app started...
+    await Task.Delay(500);
+    await example.PostStartedAndPreStoppingAsync();
 }
 
-lifetime.ApplicationStarted.Register(() => ReportHealthCheck("Started"));
-lifetime.ApplicationStopping.Register(() => ReportHealthCheck("Stopping"));
-lifetime.ApplicationStopped.Register(() => ReportHealthCheck("Stopped"));
-
-app.Run();
-
-// Sample output:
-//   info: Microsoft.Hosting.Lifetime[0]
-//         Application started. Press Ctrl+C to shut down.
-//   info: Microsoft.Hosting.Lifetime[0]
-//         Hosting environment: Production
-//   info: Microsoft.Hosting.Lifetime[0]
-//         Content root path: .\lifecycle-health-checks\bin\Debug\net8.0
-//   Started: Healthy 00:00:00.0159571
-//   info: Microsoft.Hosting.Lifetime[0]
-//         Application is shutting down...
-//   fail: Microsoft.Extensions.Diagnostics.HealthChecks.DefaultHealthCheckService[103]
-//         Health check ApplicationLifecycle with status
-//         Unhealthy completed after 0.0067ms with message 'Stopping'
-//   Stopping: Unhealthy 00:00:00.0307552
-//   fail: Microsoft.Extensions.Diagnostics.HealthChecks.DefaultHealthCheckService[103]
-//         Health check ApplicationLifecycle with status
-//         Unhealthy completed after 0.0052ms with message 'Stopping'
-//   Stopped: Unhealthy 00:00:00.0015680
+await Task.WhenAll(DelayAndRepostAsync(), app.RunAsync());