ASP.NET Core - 自訂 Health Checks Response

透前一篇： Health Checks 監控 SQL Server, WebAPI 與 Redis 健康狀態， 你大概已經知道如何監控不同的服務，但總會懷疑為什麼只能取的整體的狀態態，我們能不能看到每一個服務的狀態呢？ 答案是肯定的，本篇文章將簡單介紹如何自訂 Health Checks Response，讓所有的服務運作情況一目了然！

那有美美的圖形介面給老闆看? 答案是有的，在下一篇：ASP.NET Core Health Checks UI 圖形化介面呈現服務健康狀態 會詳細說明。

HealthChecks 內有個 HealthReport 物件存有整體狀態(Status)、整體執行時間 (TotalDuration) 與相依服務的狀態 (HealthReportEntry)。每一個 Entry 內有各自的資料(Data)、狀態(Status)、執行時間(Duration)、標籤(Tags)、例外(Exception)、描述(Description)。我們先建立自訂 Response，如下列程式碼：

	namespace HealthCheckDemo.Messages
	{
	public class HealthCheckResponse
	{
	public string Status { get; set; }
	public string TotalDuration { get; set; }
	public DependencyService[] DependencyServices { get; set; }
	}
	public class DependencyService
	{
	public string Key { get; set; }
	public string Status { get; set; }
	public string Duration { get; set; }
	public string Tags { get; set; }
	public string Exception { get; set; }
	}
	}

view raw HealthCheckResponse.cs hosted with ❤ by GitHub

在 Startup.cs 內新增一個方法 CreateHealthCheckResponse，內容如下：

	private Task CreateHealthCheckResponse(HttpContext httpContext, HealthReport result)
	{
	httpContext.Response.ContentType = "application/json";
	var response = new HealthCheckResponse()
	{
	Status = result.Status.ToString(),
	TotalDuration = result.TotalDuration.TotalSeconds.ToString("0:0.00"),
	DependencyServices = result.Entries.Select(service => new DependencyService()
	{
	Key = service.Key,
	Duration = service.Value.Duration.TotalSeconds.ToString("0:0.00"),
	Exception = service.Value.Exception?.Message,
	Status = service.Value.Status.ToString(),
	Tags = string.Join(",", service.Value.Tags?.ToArray())
	}).ToArray()
	};
	return httpContext.Response.WriteAsync(JsonConvert.SerializeObject(response, Formatting.Indented));
	}

view raw CreateHealthCheckResponse.cs hosted with ❤ by GitHub

回到 Startup.cs 的 Configure 方法，加上剛剛自訂 HealthCheck Response，更改程式碼如下：

整體程式碼樣貌如下：

	using HealthCheckDemo.Messages;
	using Microsoft.AspNetCore.Builder;
	using Microsoft.AspNetCore.Diagnostics.HealthChecks;
	using Microsoft.AspNetCore.Hosting;
	using Microsoft.AspNetCore.Http;
	using Microsoft.Extensions.Configuration;
	using Microsoft.Extensions.DependencyInjection;
	using Microsoft.Extensions.Diagnostics.HealthChecks;
	using Microsoft.Extensions.Hosting;
	using Newtonsoft.Json;
	using System;
	using System.Linq;
	using System.Threading.Tasks;
	namespace HealthCheckDemo
	{
	public class Startup
	{
	public Startup(IConfiguration configuration)
	{
	Configuration = configuration;
	}
	public IConfiguration Configuration { get; }
	// This method gets called by the runtime. Use this method to add services to the container.
	public void ConfigureServices(IServiceCollection services)
	{
	services.AddControllers();
	var redisString = "";
	services.AddDistributedRedisCache(options =>
	{
	options.InstanceName = "";
	options.Configuration = redisString;
	});
	var connectionString = Configuration.GetConnectionString("BloggingDatabase");
	var weatherServiceUri = "https://localhost:44385";
	services.AddHealthChecks()
	.AddSqlServer(connectionString)
	.AddRedis(redisString)
	.AddUrlGroup(new Uri($"{weatherServiceUri}/weatherforecast"), "Weather API Health Check", HealthStatus.Degraded, timeout: new System.TimeSpan(0,0,3));
	}
	// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
	public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
	{
	if (env.IsDevelopment())
	{
	app.UseDeveloperExceptionPage();
	}
	app.UseHttpsRedirection();
	app.UseRouting();
	app.UseAuthorization();
	app.UseEndpoints(endpoints =>
	{
	endpoints.MapControllers();
	endpoints.MapHealthChecks("/health", new HealthCheckOptions()
	{
	ResponseWriter = CreateHealthCheckResponse
	});
	});
	}
	private Task CreateHealthCheckResponse(HttpContext httpContext, HealthReport result)
	{
	httpContext.Response.ContentType = "application/json";
	var response = new HealthCheckResponse()
	{
	Status = result.Status.ToString(),
	TotalDuration = result.TotalDuration.TotalSeconds.ToString("0:0.00"),
	DependencyServices = result.Entries.Select(service => new DependencyService()
	{
	Key = service.Key,
	Duration = service.Value.Duration.TotalSeconds.ToString("0:0.00"),
	Exception = service.Value.Exception?.Message,
	Status = service.Value.Status.ToString(),
	Tags = string.Join(",", service.Value.Tags?.ToArray())
	}).ToArray()
	};
	return httpContext.Response.WriteAsync(JsonConvert.SerializeObject(response, Formatting.Indented));
	}
	}
	}

view raw Startup.cs hosted with ❤ by GitHub

接下來執行，即可看見每一個服務結果。

若您的團隊已經有既有的監控系統，您可以自己客製 CreateHealthCheckResponse，以符合監控服務需求。倘若有相關管理人員進行監控，你可以在下一篇學習如何產生圖形化介面，方便閱讀。