上一篇定義了兩種使用Jaeger的方式：中間件和action過濾器，下面這個例子定義了兩個服務 WebAPI01，請求WebAPI02，采用的是中間件的請求方式。

引入JaegerSharp包（或發(fā)布到自己的Nuget庫里引用）

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){//命名客戶端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OpenTracingservices.AddOpenTracing();//注入Jaegerif (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" }

調用下游服務 WebAPI02，下游服務 WebAPI02與WebAPI01類似，需要引入JaegerSharp，添加配置文件，指向同一個Jaeger的host，如果WebAPI02有下游API調用，繼續(xù)配置調用。

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中請求WebAPI02");var result = await GetWebAPI02();return $"WebAPI01請求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";}}} }

下載Jaeger(https://www.jaegertracing.io/download/)，我用的是1.21.0的Windows版本，因為我的開發(fā)環(huán)境是Windows，運行jaeger-all-in-one.exe

，再跑自己的應用，訪問完鏈路后，打開localhost:16686，查看結果如下：

查詢WebAPI01結果

點擊WebAPI01:HTTP GET?7151a0a結果如下，鏈路清晰

總結

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