Extensions.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Diagnostics.HealthChecks;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Diagnostics.HealthChecks;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.ServiceDiscovery;
using OpenTelemetry;
using OpenTelemetry.Metrics;
using OpenTelemetry.Trace;
using System.Text.Json;

namespace Microsoft.Extensions.Hosting;

// Adds common .NET Aspire services: service discovery, resilience, health checks, and OpenTelemetry.
// This project should be referenced by each service project in your solution.
// To learn more about using this project, see https://aka.ms/dotnet/aspire/service-defaults
public static class Extensions
{
    public static TBuilder AddServiceDefaults<TBuilder>(this TBuilder builder) where TBuilder : IHostApplicationBuilder
    {
        builder.ConfigureOpenTelemetry();

        builder.AddDefaultHealthChecks();

        builder.Services.AddServiceDiscovery();

        builder.Services.ConfigureHttpClientDefaults(http =>
        {
            // Turn on resilience by default
            http.AddStandardResilienceHandler();

            // Turn on service discovery by default
            http.AddServiceDiscovery();
        });

        // Uncomment the following to restrict the allowed schemes for service discovery.
        // builder.Services.Configure<ServiceDiscoveryOptions>(options =>
        // {
        //     options.AllowedSchemes = ["https"];
        // });

        return builder;
    }

    public static TBuilder ConfigureOpenTelemetry<TBuilder>(this TBuilder builder) where TBuilder : IHostApplicationBuilder
    {
        builder.Logging.AddOpenTelemetry(logging =>
        {
            logging.IncludeFormattedMessage = true;
            logging.IncludeScopes = true;
        });

        builder.Services.AddOpenTelemetry()
            .WithMetrics(metrics =>
            {
                metrics.AddAspNetCoreInstrumentation()
                    .AddHttpClientInstrumentation()
                    .AddRuntimeInstrumentation();
            })
            .WithTracing(tracing =>
            {
                tracing.AddSource(builder.Environment.ApplicationName)
                    .AddAspNetCoreInstrumentation()
                    // Uncomment the following line to enable gRPC instrumentation (requires the OpenTelemetry.Instrumentation.GrpcNetClient package)
                    //.AddGrpcClientInstrumentation()
                    .AddHttpClientInstrumentation();
            });

        builder.AddOpenTelemetryExporters();

        // Add browser telemetry support using OpenTelemetry Protocol (OTLP) over HTTP and CORS
        builder.Services.AddCors(options =>
        {
            options.AddPolicy("AllowAll", builder =>
            {
                builder.AllowAnyOrigin()
                       .AllowAnyMethod()
                       .AllowAnyHeader();
            });
        });

        return builder;
    }

    private static TBuilder AddOpenTelemetryExporters<TBuilder>(this TBuilder builder) where TBuilder : IHostApplicationBuilder
    {
        var useOtlpExporter = !string.IsNullOrWhiteSpace(builder.Configuration["OTEL_EXPORTER_OTLP_ENDPOINT"]);

        if (useOtlpExporter)
        {
            builder.Services.AddOpenTelemetry().UseOtlpExporter();
        }

        // Uncomment the following lines to enable the Azure Monitor exporter (requires the Azure.Monitor.OpenTelemetry.AspNetCore package)
        //if (!string.IsNullOrEmpty(builder.Configuration["APPLICATIONINSIGHTS_CONNECTION_STRING"]))
        //{
        //    builder.Services.AddOpenTelemetry()
        //       .UseAzureMonitor();
        //}

        return builder;
    }

    public static TBuilder AddDefaultHealthChecks<TBuilder>(this TBuilder builder) where TBuilder : IHostApplicationBuilder
    {
        builder.Services.AddHealthChecks()
            // Add a default liveness check to ensure app is responsive
            .AddCheck("self", () => HealthCheckResult.Healthy(), ["live"]);

        return builder;
    }

    public static WebApplication MapDefaultEndpoints(this WebApplication app)
    {
        // Adding health checks endpoints to applications in non-development environments has security implications.
        // See https://aka.ms/dotnet/aspire/healthchecks for details before enabling these endpoints in non-development environments.
        if (app.Environment.IsDevelopment())
        {
            // All health checks must pass for app to be considered ready to accept traffic after starting
            app.MapHealthChecks("/health");

            // Only health checks tagged with the "live" tag must pass for app to be considered alive
            app.MapHealthChecks("/alive", new HealthCheckOptions
            {
                Predicate = r => r.Tags.Contains("live")
            });
        }
        else
        {
            // Considerations for non-development environments
            app.MapHealthChecks("/health", new HealthCheckOptions
            {
                Predicate = _ => true,
                ResponseWriter = async (context, report) =>
                {
                    context.Response.ContentType = "application/json";
                    var result = JsonSerializer.Serialize(new
                    {
                        status = report.Status.ToString(),
                        checks = report.Entries.Select(e => new
                        {
                            name = e.Key,
                            status = e.Value.Status.ToString(),
                            exception = e.Value.Exception?.Message,
                            duration = e.Value.Duration.ToString()
                        })
                    });
                    await context.Response.WriteAsync(result);
                }
            });

            app.MapHealthChecks("/alive", new HealthCheckOptions
            {
                Predicate = r => r.Tags.Contains("live"),
                ResponseWriter = async (context, report) =>
                {
                    context.Response.ContentType = "application/json";
                    var result = JsonSerializer.Serialize(new
                    {
                        status = report.Status.ToString(),
                        checks = report.Entries.Select(e => new
                        {
                            name = e.Key,
                            status = e.Value.Status.ToString(),
                            exception = e.Value.Exception?.Message,
                            duration = e.Value.Duration.ToString()
                        })
                    });
                    await context.Response.WriteAsync(result);
                }
            });
        }

        return app;
    }
}