.NET6之MiniAPI(十三)：健康检查

程序员开发程序，是“生”的过程，运维人员负责日常运维，是“养”的过程，在养的过程，运维人员希望在第一时间了解程序的状况，健康检查，是最基础的手段。

var builder = WebApplication.CreateBuilder(args);//注入健康检查服务builder.Services.AddHealthChecks();var app = builder.Build();app.MapGet("/test", () =>{    return DateTime.Now;});//添加中间件，设置健康检查的访问路径是/healthapp.MapHealthChecks("/health");app.Run();

还可以通过重写来改变返回的字符串：

app.MapHealthChecks("/health", new HealthCheckOptions{    ResponseWriter = (context, result) =>   {       var backContent = "this is health";       return context.Response.WriteAsync(backContent);   }});

当然，这样的健康检查只是host有没有启动，如果有更深层次的检查，可以通过实现IHealthCheck来实现。

using Microsoft.Extensions.Diagnostics.HealthChecks;var builder = WebApplication.CreateBuilder(args);//注入自定义健康检查类builder.Services.AddHealthChecks()   .AddCheck<TestHealthCheck>("test_health_check");var app = builder.Build();app.MapGet("/test", () =>{    return DateTime.Now;});//添加中间件，设置健康检查的访问路径是/healthapp.MapHealthChecks("/health");app.Run();public class TestHealthCheck : IHealthCheck{    public Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)    {       //这是一个三方的获取空闲内存的库        var client = new MemoryMetricsClient();        var metrics = client.GetMetrics();             Console.WriteLine("Free : " + metrics.Free);        //假业务要求，内存大于1000M，就健康        var healthCheckResultHealthy = metrics.Free > 1000;        if (healthCheckResultHealthy)        {            return Task.FromResult(                HealthCheckResult.Healthy("healthy"));        }        return Task.FromResult(            new HealthCheckResult(context.Registration.FailureStatus,            "unhealthy"));    }}

有了这个实现，就可以很方便地实现业务中的各种判定服务是否健康了。

上面的所有健康检查都是拉模式，意思就是外部监控服务会请求本服务的/health，获取信息，来判定是否健康，在asp.net core也提供了推的模式，如下：

using Microsoft.Extensions.Diagnostics.HealthChecks;using MiniDemo05;var builder = WebApplication.CreateBuilder(args);builder.Services.AddHealthChecks()   .AddCheck<TestHealthCheck>("test_health_check");//配置推送的参数builder.Services.Configure<HealthCheckPublisherOptions>(options =>{    options.Delay = TimeSpan.FromSeconds(1);    options.Period = TimeSpan.FromSeconds(5);});//注入推送服务builder.Services.AddSingleton<IHealthCheckPublisher, HealthPublisher>();var app = builder.Build();app.MapGet("/test", () =>{    return DateTime.Now;});app.Run();public class TestHealthCheck : IHealthCheck{    public Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)    {        var client = new MemoryMetricsClient();        var metrics = client.GetMetrics();        Console.WriteLine("Total: " + metrics.Total);        Console.WriteLine("Used : " + metrics.Used);        Console.WriteLine("Free : " + metrics.Free);        var healthCheckResultHealthy = metrics.Free > 6000;        if (healthCheckResultHealthy)        {            return Task.FromResult(                HealthCheckResult.Healthy("healthy"));        }        return Task.FromResult(            new HealthCheckResult(context.Registration.FailureStatus,            "unhealthy"));    }}public class HealthPublisher : IHealthCheckPublisher{    private readonly ILogger<HealthPublisher> _logger;    public HealthPublisher(ILogger<HealthPublisher> logger)    {        _logger = logger;    }    public Task PublishAsync(HealthReport report, CancellationToken cancellationToken)    {        _logger.LogInformation($"{DateTime.Now.ToString()},{ report.Status}");        return Task.CompletedTask;    }}

如果监控参数收集是一个url，我们可以在HealthPublisher中把健康的结果推送上去。