.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/health
app.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/health
app.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。

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