.NET6之MiniAPI(二十八)：Tracing

　　Log，Metrics，Tracing是为服务正常运行保驾护航的三件套，前面有介绍过Log和Metrics，本篇说明说一下Tracing。Tracing的思路和Metrics一样，通过三方服务，来达成效果，这里选用的是Jaeger，通过在MiniAPI项目中引入Jaeger和OpenTracing的库，来向Jaeger推送跟踪数据，通过访问http://localhost:16686/search，来查看跟踪结果。

 　　Jaeger下载地址：

​​　　https://www.jaegertracing.io/download/​​

　　接来了定议两个项目，Order项目和Stock项目，Order通过httpclient调用Stock来查看商品库存，这样，两个项目就开成了一个调用链路。

Order项目

using Jaeger;
using OpenTracing.Propagation;
using OpenTracing;
using OpenTracing.Util;
using Jaeger.Samplers;
using Jaeger.Senders.Thrift;
using Jaeger.Senders;
using Jaeger.Reporters;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddHttpClient();
//注入OpenTracing服务
builder.Services.AddOpenTracing();
builder.Services.AddSingleton<ITracer>(serviceProvider =>
{
    var serviceName = serviceProvider.GetRequiredService<IWebHostEnvironment>().ApplicationName;
    var loggerFactory = serviceProvider.GetRequiredService<ILoggerFactory>();
    //配置跟踪
    Jaeger.Configuration.SenderConfiguration.DefaultSenderResolver = new SenderResolver(loggerFactory)
        .RegisterSenderFactory<ThriftSenderFactory>();  
    var tracer = new Tracer.Builder(serviceName)
        //添加日志框架
        .WithLoggerFactory(loggerFactory)
        //添加数据采集器
        .WithSampler(new ConstSampler(true))   
        .Build();
    //注册全局跟踪器
    GlobalTracer.Register(tracer);
    return tracer;
});

var app = builder.Build();

app.MapGet("/order", async (ILogger<Program> logger, IHttpClientFactory clientFactory, ITracer tracer) =>
{
    using (var scope = tracer.BuildSpan("订单系统").StartActive(true))
    {
        logger.LogInformation("订单查询库存");
        var client = clientFactory.CreateClient();
        var content = await client.GetStringAsync("http://localhost:5160/stock/D0001");
        return $"stock调用结果：{content}";
    }
});

app.Run();

Stock项目

using Jaeger;
using Jaeger.Reporters;
using Jaeger.Samplers;
using Jaeger.Senders;
using Jaeger.Senders.Thrift;
using OpenTracing;
using OpenTracing.Util;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddOpenTracing();
builder.Services.AddSingleton<ITracer>(serviceProvider =>
{
    var serviceName = serviceProvider.GetRequiredService<IWebHostEnvironment>().ApplicationName;
    var loggerFactory = serviceProvider.GetRequiredService<ILoggerFactory>();
    Jaeger.Configuration.SenderConfiguration.DefaultSenderResolver = new SenderResolver(loggerFactory)
        .RegisterSenderFactory<ThriftSenderFactory>();
    var tracer = new Tracer.Builder(serviceName)
        .WithLoggerFactory(loggerFactory)
        .WithSampler(new ConstSampler(true))
        .Build();
    GlobalTracer.Register(tracer);
    return tracer;
});
var app = builder.Build();

app.MapGet("/stock/{no}", (string no, ILogger<Program> logger, ITracer tracer) =>
{
    using (var scope = tracer.BuildSpan("库存系统").StartActive(true))
    {
        logger.LogInformation("按{0}查询库存", no);
        return new Product { No = no, Quantity = 1324, Name = "Surface Go 3" };
    }
});
app.Run();

public class Product
{
    public string? No { get; set; }
    public string? Name { get; set; }
    public int Quantity { get; set; }
}

　　用命令行运行下载的jaeger-all-in-one.exe，在浏览器或postman访问Order项目的/order地址，再进入Jaeger，查看结果：http://localhost:16686/search

 通过上面的UI，可以很方便地查看请求链条上的调用，当调用关系很复杂时，特别有用。

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