1. 探针集成实现高可用

• Liveness
• Readiness
• Startup

1.1 LivenessProbe

• 判断服务是否存活
• 结束“非存活”状态服务
• 根据重启策略决定是否重启服务

1.2 ReadinessProbe

• 判断服务是否“就绪”
• “就绪”状态的服务可以接收请求
• 非“就绪”状态的服务将会被从流量负载中摘除

1.3 StartupProbe

• 检测应用程序是否启动成功
• 启动探针执行成功后，将不再执行，除非应用重启
• 当启动探针检测成功后，其它探针才开始工作
• 适合启动较慢的应用配置
• Kuberbetes 1.16以后的支持

// startup
internal static bool Ready { get; set; } = true;
internal static bool Live { get; set; } = true;

public void ConfigureServices(IServiceCollection services)
{
	...
	// 注册健康检查
	services.AddHealthChecks()
            .AddMySql(Configuration.GetValue<string>("Mysql"), "mysql", tags: new string[] { "mysql", "live", "all" })// tags标签分组
             .AddRabbitMQ(s =>
             {
                 var connectionFactory = new RabbitMQ.Client.ConnectionFactory();
                 Configuration.GetSection("RabbitMQ").Bind(connectionFactory);
                 return connectionFactory;
             }, "rabbitmq", tags: new string[] { "rabbitmq", "live", "all" })
             .AddCheck("liveChecker", () =>
             {
                 return Live ? HealthCheckResult.Healthy() : HealthCheckResult.Unhealthy();
             }, new string[] { "live", "all" })
             .AddCheck("readyChecker", () =>
             {
                 return Ready ? HealthCheckResult.Healthy() : HealthCheckResult.Unhealthy();
             }, new string[] { "ready", "all" });
}

// 
 public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
 {
 	...
 	app.UseEndpoints(endpoints =>
            {
                endpoints.MapMetrics();
                endpoints.MapHealthChecks("/live", new HealthCheckOptions { Predicate = registration => registration.Tags.Contains("live") });// 检查标记了live的检查项
                endpoints.MapHealthChecks("/ready", new HealthCheckOptions { Predicate = registration => registration.Tags.Contains("ready") });
                endpoints.MapHealthChecks("/hc", new Microsoft.AspNetCore.Diagnostics.HealthChecks.HealthCheckOptions
                {
                    ResponseWriter = HealthChecks.UI.Client.UIResponseWriter.WriteHealthCheckUIResponse
                });// 没有传检查项，检查所有
                endpoints.MapControllers();
                endpoints.MapGrpcService<GeekTime.Ordering.API.Grpc.OrderServiceImpl>();
            });
 }
 
 // Controller调用
 // 设置Ready的值
 [HttpGet]
 public IActionResult SetReady([FromQuery]bool ready)
 {
     Startup.Ready = ready;
     if (!ready)
     {
         Task.Run(async () =>
         {
             await Task.Delay(60000);
             Startup.Ready = true;
         });
     }
     return Content($"{Environment.MachineName} : Ready={Startup.Ready}");
 }
 
 // 设置live
[HttpGet]
public IActionResult SetLive([FromQuery]bool live)
 {
     Startup.Live = live;
     return Content($"{Environment.MachineName} : Live={Startup.Live}");
 }

// 程序退出
[HttpGet]
public IActionResult Exit([FromServices]IHostApplicationLifetime application)
  {
      Task.Run(async () =>
      {
          await Task.Delay(3000);
          application.StopApplication();
      });
      return Content($"{Environment.MachineName} : Stopping");
  }

2. 健康检查看板

AspNetCore.Diagnostics.HealthCheck项目，开源社区项目插件

2.1 组件包

• 探针检测端：AspNetCore.HealthChecks.UI
• 应用端输出：AspNetCore.HealthChecks.UI.Client
• 应用端检查项：AspNetCore.HealthChecks.Xxx

// startup
public void ConfigureServices(IServiceCollection services)
{
     services.AddMvc();
     services.AddHealthChecks();
     services.AddHealthChecksUI();
 }

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
       if (env.IsDevelopment())
       {
           app.UseDeveloperExceptionPage();
       }

       app.UseRouting();
       app.UseEndpoints(endpoints =>
       {
           endpoints.MapHealthChecks("/live");
           endpoints.MapHealthChecks("/ready");
           endpoints.MapHealthChecks("/hc");
           endpoints.MapMetrics();
           endpoints.MapHealthChecksUI();// 使得dashboard生效
           endpoints.MapControllers();
       });
   }

// 配置文件配置需要检查的项目
"HealthChecksUI": {
    "HealthChecks": [
      {
        "Name": "geektime-ordering-api",
        "Uri": "http://geektime-ordering-api/hc"
      },
      {
        "Name": "geektime-mobile-apiaggregator",
        "Uri": "http://geektime-mobile-apiaggregator/hc"
      },
      {
        "Name": "geektime-mobile-gateway",
        "Uri": "http://geektime-mobile-gateway/hc"
      }
    ],