How to add Health Checks to ASP.NET Core project. A coding story.

public class Startup{   public IConfiguration Configuration { get; set; }   public Startup(IConfiguration configuration)   {      this.Configuration = configuration;   }   public void ConfigureServices(IServiceCollection services)   {      var connectionString = this.Configuration.GetConnectionString("DefaultConnection");      var rabbitMqConnectionString = this.Configuration.GetConnectionString("RabbitMQ");      var downstreamServiceUrl = this.Configuration["DownstreamService:BaseUrl"];      services.AddHealthChecks()            .AddSqlServer(               connectionString,               name: "Database",               failureStatus: HealthStatus.Degraded,               timeout: TimeSpan.FromSeconds(1),               tags: new string[] { "services" })            .AddRabbitMQ(               rabbitMqConnectionString,               name: "RabbitMQ",               failureStatus: HealthStatus.Degraded,               timeout: TimeSpan.FromSeconds(1),               tags: new string[] { "services" })            .AddUrlGroup(               new Uri($"{downstreamServiceUrl}/health"),               name: "Downstream API Health Check",               failureStatus: HealthStatus.Unhealthy,               timeout: TimeSpan.FromSeconds(3),               tags: new string[] { "services" });   }   public void Configure(IApplicationBuilder app)   {      app.UseRouting();      app.UseEndpoints(endpoints =>      {            endpoints.MapCustomHealthCheck();            endpoints.MapGet("/{**path}", async context =>            {               await context.Response.WriteAsync(                  "Navigate to /health to see the health status.");            });      });   }}

public static class EndpointRouteBuilderExtensions{   /// <summary>   /// Adds a Health Check endpoint to the <see cref="IEndpointRouteBuilder"/> with the specified template.   /// </summary>   /// <param name="endpoints">The <see cref="IEndpointRouteBuilder"/> to add endpoint to.</param>   /// <param name="pattern">The URL pattern of the liveness endpoint.</param>   /// <param name="servicesPattern">The URL pattern of the readiness endpoint.</param>   /// <returns></returns>   public static IEndpointRouteBuilder MapCustomHealthCheck(      this IEndpointRouteBuilder endpoints,      string pattern = "/health",      string servicesPattern = "/health/ready")   {      if (endpoints == null)      {            throw new ArgumentNullException(nameof(endpoints));      }      endpoints.MapHealthChecks(pattern, new HealthCheckOptions()      {            Predicate = (check) => !check.Tags.Contains("services"),            AllowCachingResponses = false,            ResponseWriter = WriteResponse,      });      endpoints.MapHealthChecks(servicesPattern, new HealthCheckOptions()      {            Predicate = (check) => true,            AllowCachingResponses = false,            ResponseWriter = WriteResponse,      });      return endpoints;   }   private static Task WriteResponse(HttpContext context, HealthReport result)   {      context.Response.ContentType = "application/json; charset=utf-8";      var options = new JsonWriterOptions      {            Indented = true      };      using var stream = new MemoryStream();      using (var writer = new Utf8JsonWriter(stream, options))      {            writer.WriteStartObject();            writer.WriteString("status", result.Status.ToString());            writer.WriteStartObject("results");            foreach (var entry in result.Entries)            {               writer.WriteStartObject(entry.Key);               writer.WriteString("status", entry.Value.Status.ToString());               writer.WriteEndObject();            }            writer.WriteEndObject();            writer.WriteEndObject();      }      var json = Encoding.UTF8.GetString(stream.ToArray());      return context.Response.WriteAsync(json);   }}