引入Jaeger——使用

　　上一篇定义了两种使用Jaeger的方式：中间件和action过滤器，下面这个例子定义了两个服务 WebAPI01，请求WebAPI02，采用的是中间件的请求方式。

引入JaegerSharp包（或发布到自己的Nuget库里引用）

WebAPI01的Startup

using JaegerSharp;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.OpenApi.Models;
using System;

namespace WebAPI01
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }
        public IConfiguration Configuration { get; }
        public void ConfigureServices(IServiceCollection services)
        {
            //命名客户端
            services.AddHttpClient("WebAPI02", client =>
            {
                client.BaseAddress = new Uri(Configuration.GetSection("DownStreamUrl").Value);
            });
            services.AddControllers();
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "WebAPI01", Version = "v1" });
            });
            //添加OpenTracing
            services.AddOpenTracing();
            //注入Jaeger
            if (Convert.ToBoolean(Configuration.GetSection("OpenTracing:Enable")?.Value))
            {
                var agentHost = Configuration.GetSection("OpenTracing:Agent").GetValue<string>("Host");
                var agentPort = Configuration.GetSection("OpenTracing:Agent").GetValue<int>("Port");
                var agentMaxPacketSize = Configuration.GetSection("OpenTracing:Agent").GetValue<int>("MaxPacketSize");
                services.AddJaegerSharp(agentHost, agentPort, agentMaxPacketSize);
            }
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseSwagger();
                app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "WebAPI01 v1"));
            }

            app.UseHttpsRedirection();
            if (Convert.ToBoolean(Configuration.GetSection("OpenTracing:Enable")?.Value))
            {
                app.UseJaegerSharp();
            }
            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

WebAPI01的appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "OpenTracing": {
    "Enable": true,
    "Agent": {
      "Host": "localhost",
      "Port": 6831,
      "MaxPacketSize": 0
    }
  },
  "DownStreamUrl": "https://localhost:6001"
}

　　调用下游服务 WebAPI02，下游服务 WebAPI02与WebAPI01类似，需要引入JaegerSharp，添加配置文件，指向同一个Jaeger的host，如果WebAPI02有下游API调用，继续配置调用。

using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using System.Net.Http;
using System.Threading.Tasks;

namespace WebAPI01.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class HomeController : ControllerBase
    {
        private readonly IHttpClientFactory _clientFactory;
        private readonly ILogger<HomeController> _logger;

        public HomeController(ILogger<HomeController> logger, IHttpClientFactory clientFactory)
        {
            _clientFactory = clientFactory;
            _logger = logger;
        }

        [HttpGet]
        public async Task<string> Get()
        {
            _logger.LogInformation("WebAPI01中请求WebAPI02");
            var result = await GetWebAPI02();
            return $"WebAPI01请求WebAPI02返回值 :{ result}";
        }

        async Task<string> GetWebAPI02()
        {
            using var client = _clientFactory.CreateClient("WebAPI02");
            var request = new HttpRequestMessage(HttpMethod.Get, "/home");
            using var response = await client.SendAsync(request);
            if (response.IsSuccessStatusCode)
            {
                var result = await response.Content.ReadAsStringAsync();
                return result;
            }
            else
            {
                return "error";
            }
        }
    }
}

下载Jaeger(https://www.jaegertracing.io/download/)，我用的是1.21.0的Windows版本，因为我的开发环境是Windows，运行jaeger-all-in-one.exe

，再跑自己的应用，访问完链路后，打开localhost:16686，查看结果如下：

查询WebAPI01结果

 点击WebAPI01:HTTP GET 7151a0a结果如下，链路清晰

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