C#配置Eureka Client的教训

因为需要将毕设算法模块接入到一个现有的微服务系统中，我需要将我的项目包装成一个Eureka Client，并通过Eureka提供的Service Discovery来完成对其它微服务的调用。又由于我的毕设采用C#完成，需要借助开源项目SteelToe来完成。但是在开发过程中发生了一个折磨了我四天的问题，原来是配置错误导致的

为了便于测试，我们可以直接利用配置好的一个Eureka Server镜像：

docker pull steeltoeoss/eureka-server
docker run --publish 8761:8761 steeltoeoss/eureka-server

Eureka Server最好在Client之前上线。

客户端1：被调用者FakeExternalSystem

在基础的模板上，我们还需要做出如下更改：

项目文件：xxx.csproj

  <ItemGroup>
    ......
    <PackageReference Include="Steeltoe.Discovery.ClientCore" Version="3.1.3" />
    <PackageReference Include="Steeltoe.Discovery.Eureka" Version="3.1.3" />
    <PackageReference Include="Steeltoe.Extensions.Logging.DynamicSerilogBase" Version="3.1.3" />
    <PackageReference Include="Steeltoe.Management.EndpointCore" Version="3.1.3" />
    <PackageReference Include="Steeltoe.Management.TracingCore" Version="3.1.3" />
  </ItemGroup>

主文件：Program.cs

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services
    .AddEndpointsApiExplorer()
    .AddSwaggerGen()
    .PostConfigure<AspNetCoreInstrumentationOptions>(options =>
    {
        options.Enrich = (activity, eventName, rawObject) =>
        {
            if (eventName.Equals("OnStartActivity"))
            {
                if (rawObject is HttpRequest httpRequest)
                {
                    activity.SetTag("requestProtocol", httpRequest.Protocol);
                }
            }
        };
    })
    .AddControllers();

builder.WebHost
    .ConfigureLogging((builderContext, loggingBuilder) =>
    {
        // Add Serilog Dynamic Logger
        loggingBuilder.AddDynamicSerilog();
    })
    .AddHealthActuator()
    .AddInfoActuator()
    .AddLoggersActuator()
    .AddServiceDiscovery(options => options.UseEureka())
    ;

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();

}

app.MapControllers();
app.Run();

应用配置：appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "spring": {
    "application": {
      "name": "WeatherForecast"
    }
  },
  "eureka": {
    "client": {
      "serviceUrl": "http://localhost:8761/eureka/",
      "shouldFetchRegistry": "false",//WeatherForecast不会调用其它服务，可以设为false
      "shouldRegisterWithEureka": true,
      "validateCertificates": false
    },
    "instance": {
      "port": "8080",//这里需要和launchsettings里一致
      "ipAddress": "localhost",//如果用docker的话，记得改成172那个docker内网地址
      "preferIpAddress": true
    }
  },
  "AllowedHosts": "*"
}

客户端2：调用者Dsc.Server

项目文件和Program.cs的变动和上一节相同，但是要注意把自己写的服务Inject进去(这里的服务是InternalServiceProvider)，并注入DiscoveryHttpMessageHandler和HttpClientFactory。

Program.cs

......
//Transient
builder.Services.AddTransient<DiscoveryHttpMessageHandler>();
//注入用于InternalServiceProvider的HttpClientFactory
builder.Services.AddHttpClient<InternalServiceProvider>()
//为Factory生成的Client自定义Handler
    .AddHttpMessageHandler<DiscoveryHttpMessageHandler>();
//自己写的服务
builder.Services.AddSingleton<InternalServiceProvider>();
......

InternalServiceProvider.cs

public class InternalServiceProvider
{
    private readonly ILogger<InternalServiceProvider> _logger;
    private readonly IHttpClientFactory _http;

    public InternalServiceProvider(
        ILogger<InternalServiceProvider> logger,
        IHttpClientFactory http)
    {
        _logger = logger;
        _http = http;
    }
    public async ValueTask<string> GetStringAsync(
        string serviceName,string ifName)
    {
        return await _http.CreateClient(nameof(InternalServiceProvider)).GetStringAsync($"http://{serviceName}/{ifName}");
    }
}

然后我们在控制器里给一个这样的Api：

  [HttpGet("")]
  public async Task<ActionResult<string>> Get()
  {
      return await _internalServiceProvider.GetStringAsync("WeatherForecast", "WeatherForecast");
  }

最关键的还是应用配置：appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "spring": {
    "application": {
      "name": "Dsc"
    }
  },
  "eureka": {
    "client": {
      "serviceUrl": "http://localhost:8761/eureka/",
      "shouldFetchRegistry": "true",//非常关键，因为我们需要调用其他服务，所以一定一定要设为true！！！
      "shouldRegisterWithEureka": true,
      "validateCertificates": false
    },
    "instance": {
      "port": "8081",
      "ipAddress": "localhost",
      "preferIpAddress": true
    }
  },
  "AllowedHosts": "*"
}

使用docker

你可以这样获取每个容器的ip地址：

docker inspect --format='{{.Name}} - {{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' $(docker ps -aq)

然后把appsettings.json的eureka:instance:ipAddress改为容器地址，端口号改为80即可。