.NET中的健康检查(Health Checks)是什么？如何在微服务中实现它？

Install-Package Microsoft.Extensions.Diagnostics.HealthChecks.EntityFrameworkCore

builder.Services.AddHealthChecks()
    .AddDbContextCheck<AppDbContext>() // 检查数据库上下文
    .AddRedis("redisConnectionString", name: "redis") // 检查 Redis
    .AddUrlGroup(new Uri("https://api.external.com/health"), name: "external-api");

// 启用健康检查中间件
app.MapHealthChecks("/health");
app.MapHealthChecks("/health-details", new HealthCheckOptions()
{
    ResponseWriter = WriteDetailedResponse // 输出详细信息（谨慎用于生产）
});

static Task WriteDetailedResponse(HttpContext context, HealthReport report)
{
    context.Response.ContentType = "application/json";
    var response = new
    {
        Status = report.Status,
        Checks = report.Entries.Select(e => new
        {
            e.Key,
            e.Value.Status,
            e.Value.Description
        })
    };
    return context.Response.WriteAsJsonAsync(response);
}

livenessProbe:
  httpGet:
    path: /health
    port: 80
  initialDelaySeconds: 30
  periodSeconds: 10

readinessProbe:
  httpGet:
    path: /health
    port: 80
  initialDelaySeconds: 5
  periodSeconds: 5

public class CustomHealthCheck : IHealthCheck
{
    public async Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)
    {
        // 自定义逻辑：比如检查磁盘空间、外部服务凭证等
        var isHealthy = await SomeBusinessCondition();
        if (isHealthy)
            return HealthCheckResult.Healthy("Custom check passed.");
        
        return HealthCheckResult.Unhealthy("Custom check failed.");
    }
}

services.AddHealthChecks().AddCheck<CustomHealthCheck>("custom");