当前位置:首页 » ASP.NET技术教程

Asp.Net Core API网关Ocelot

2017-11-15 18:20 本站整理 浏览(3)

首先,让我们简单了解下什么是API网关?

  API网关是一个服务器,是系统的唯一入口。从面向对象设计的角度看,它与外观模式类似。API网关封装了系统内部架构,为每个客户端提供一个定制的API。它可能还具有其它职责,如身份验证、监控、负载均衡、缓存、请求分片与管理、静态响应处理。
    API网关方式的核心要点是,所有的客户端和消费端都通过统一的网关接入微服务,在网关层处理所有的非业务功能。通常,网关也是提供REST/HTTP的访问API。服务端通过API-GW注册和管理服务。

其次,我们了解下Ocelot框架

Ocelot的目标是使用.NET运行微服务/面向服务架构,我们需要一个统一的入口进入我们的系统。

Ocelot是一堆特定顺序的中间件。

Ocelot框架内部集成了IdentityServer和Consul(服务注册发现)。

Ocelot开源地址:https://github.com/TomPallister/Ocelot

接下来,我们就针对Ocelot的具体用法展开介绍。

这里使用的Ocelot版本为2.0,.Net Core版本2.0

1、搭建Asp.net Core WebApi项目,引用Ocelot.dll。

Nuget控制台,执行Ocelot安装。

PM>Install-Package Ocelot
GET https://api.nuget.org/v3/registration3-gz-semver2/ocelot/index.json
  OK https://api.nuget.org/v3/registration3-gz-semver2/ocelot/index.json 104 毫秒
  GET https://api.nuget.org/v3/registration3-gz-semver2/ocelot/page/1.5.0-unstable0134/2.0.0.json
  OK https://api.nuget.org/v3/registration3-gz-semver2/ocelot/page/1.5.0-unstable0134/2.0.0.json 108 毫秒
正在还原 J:\Demo\RichCodeBox\APIGatewayApp\APIGatewayApp.csproj 的包...
  GET https://api.nuget.org/v3-flatcontainer/ocelot/index.json
  OK https://api.nuget.org/v3-flatcontainer/ocelot/index.json 476 毫秒
  GET https://api.nuget.org/v3-flatcontainer/ocelot/2.0.0/ocelot.2.0.0.nupkg
  OK https://api.nuget.org/v3-flatcontainer/ocelot/2.0.0/ocelot.2.0.0.nupkg 125 毫秒
  GET https://api.nuget.org/v3-flatcontainer/identityserver4.accesstokenvalidation/index.json
  GET https://api.nuget.org/v3-flatcontainer/cachemanager.core/index.json
  GET https://api.nuget.org/v3-flatcontainer/cachemanager.microsoft.extensions.configuration/index.json
  GET https://api.nuget.org/v3-flatcontainer/cachemanager.microsoft.extensions.logging/index.json
  GET https://api.nuget.org/v3-flatcontainer/consul/index.json
  GET https://api.nuget.org/v3-flatcontainer/polly/index.json
  GET https://api.nuget.org/v3-flatcontainer/identityserver4/index.json
  OK https://api.nuget.org/v3-flatcontainer/identityserver4.accesstokenvalidation/index.json 133 毫秒
  GET https://api.nuget.org/v3-flatcontainer/identityserver4.accesstokenvalidation/2.1.0/identityserver4.accesstokenvalidation.2.1.0.nupkg
  OK https://api.nuget.org/v3-flatcontainer/cachemanager.microsoft.extensions.logging/index.json 286 毫秒
  OK https://api.nuget.org/v3-flatcontainer/polly/index.json 287 毫秒
  OK https://api.nuget.org/v3-flatcontainer/identityserver4.accesstokenvalidation/2.1.0/identityserver4.accesstokenvalidation.2.1.0.nupkg 160 毫秒
  GET https://api.nuget.org/v3-flatcontainer/cachemanager.microsoft.extensions.logging/1.1.1/cachemanager.microsoft.extensions.logging.1.1.1.nupkg

2、修改Startup程序。

   /// <summary>
        /// 
        /// </summary>
        /// <param name="environment"></param>
        public Startup(IHostingEnvironment environment)
        {
            var builder = new Microsoft.Extensions.Configuration.ConfigurationBuilder();
            builder.SetBasePath(environment.ContentRootPath)
                   .AddJsonFile("appsettings.json", false, reloadOnChange: true)
                   .AddJsonFile($"appsettings.{environment.EnvironmentName}.json", optional: false, reloadOnChange: true)
                   .AddJsonFile("configuration.json", optional: false, reloadOnChange: true)
                   .AddEnvironmentVariables();


            Configuration = builder.Build();
        }
 /// <summary>
        ///modified:配置
        /// </summary>
        public IConfigurationRoot Configuration { get; }

        /// <summary>
        /// 配置服务
        /// </summary>
        /// <param name="services"></param>
        public void ConfigureServices(IServiceCollection services)
        {
            Action<ConfigurationBuilderCachePart> settings = (x) =>
            {
                x.WithMicrosoftLogging(log =>
                {
                    log.AddConsole(LogLevel.Debug);

                }).WithDictionaryHandle();
            };
            services.AddOcelot(Configuration, settings);
            //services.AddMvc();
        }

        /// <summary>
        /// 配置Ocelot
        /// </summary>
        /// <param name="app"></param>
        /// <param name="env"></param>
        public async void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            //if (env.IsDevelopment())
            //{
            //    app.UseDeveloperExceptionPage();
            //}
            await app.UseOcelot();
            //app.UseMvc();
        }
        /// <summary>
        /// 入口程序
        /// </summary>
        /// <param name="args"></param>
        public static void Main(string[] args)
        {
            IWebHostBuilder builder = new WebHostBuilder();
            builder.ConfigureServices(s =>
            {
                s.AddSingleton(builder);
            });
            builder.UseKestrel()
                   .UseContentRoot(Directory.GetCurrentDirectory())
                   .UseIISIntegration()
                   .UseStartup<Startup>()
                   .UseApplicationInsights();
            var host = builder.Build();
            host.Run();
        }

3、配置Ocelot。

我们新建一个名为configuration的json文件,配置如下:

{
  "ReRoutes": [
    {
      "DownstreamPathTemplate": "/api/values",
      "DownstreamScheme": "http",
      "DownstreamHost": "localhost",
      "DownstreamPort": 8801,
      "UpstreamPathTemplate": "/api/values",
      "UpstreamHttpMethod": [ "Get" ],
      "QoSOptions": {
        "ExceptionsAllowedBeforeBreaking": 3,
        "DurationOfBreak": 10,
        "TimeoutValue": 5000
      },
      "HttpHandlerOptions": {
        "AllowAutoRedirect": false,
        "UseCookieContainer": false
      },
      "AuthenticationOptions": {

      }
    },
    {
      "DownstreamPathTemplate": "/api/product",
      "DownstreamScheme": "http",
      "DownstreamPort": 8802,
      "DownstreamHost": "localhost",
      "UpstreamPathTemplate": "/api/product",
      "UpstreamHttpMethod": [ "Get" ],
      "QoSOptions": {
        "ExceptionsAllowedBeforeBreaking": 3,
        "DurationOfBreak": 10,
        "TimeoutValue": 5000
      },
      "AuthenticationOptions": {

      }
    }
  ],
  "GlobalConfiguration": {
    "RequestIdKey": "OcRequestId",
    "AdministrationPath": "/admin"
  }
}

在这里,我们配置了两个服务,端口分别为8801和8802的。

Ocelot支持负载均衡(提供轮询、最少访问)。Ocelot大部分功能,都可以通过中间件来完成,也可以实现和重写中间件。

Ocelot原理非常简单,这里的配置文件,体现了上游请求和下游服务间的映射关系,你可以理解为,上游是客户端直接调用的URL ,下游,则是对应我们开发的服务。

4、新增两个WebApi项目,分别为APIUserServiec和APIProductService。

API服务 端口(Port)
APIUserServiec 8801
APIProductService 8802

解决方案如下:

5、配置VS启动端口:

依次类推,分别设置端口。

6、启动项目。

配置多个项目启动。

F5启动项目。

再通过API网关,访问商品服务:http://localhost:5000/api/product。

常见问题:

首次在启动API网关时,触发以下错误。

Sequence contains no matching element

根据错误详细信息,可知原因是由于系统调用AddIdentityServer方法时,触发异常。

刚开始,怀疑是配置文件configuration.json文件配置导致的,Ocelot2.0版,采用官方配置仍然触发该异常,由此排除这种可能。接下来,直接从github上克隆源代码,查看。

找到触发错误的地方,

private static void AddIdentityServer(this IServiceCollection services, IIdentityServerConfiguration identityServerConfiguration, IConfigurationRoot configurationRoot) 
        {
            services.TryAddSingleton<IIdentityServerConfiguration>(identityServerConfiguration);
            services.TryAddSingleton<IHashMatcher, HashMatcher>();
            var identityServerBuilder = services
                .AddIdentityServer(o => {
                    o.IssuerUri = "Ocelot";
                })
                .AddInMemoryApiResources(Resources(identityServerConfiguration))
                .AddInMemoryClients(Client(identityServerConfiguration))
                .AddResourceOwnerValidator<OcelotResourceOwnerPasswordValidator>();

            //todo - refactor a method so we know why this is happening
            var whb = services.First(x => x.ServiceType == typeof(IWebHostBuilder));//这个地方触发了错误
            var urlFinder = new BaseUrlFinder((IWebHostBuilder)whb.ImplementationInstance);
            var baseSchemeUrlAndPort = urlFinder.Find();
            JwtSecurityTokenHandler.DefaultInboundClaimTypeMap.Clear();

            services.AddAuthentication(IdentityServerAuthenticationDefaults.AuthenticationScheme)
                .AddIdentityServerAuthentication(o =>
                {
                    var adminPath = configurationRoot.GetValue("GlobalConfiguration:AdministrationPath", string.Empty);
                    o.Authority = baseSchemeUrlAndPort + adminPath;
                    o.ApiName = identityServerConfiguration.ApiName;
                    o.RequireHttpsMetadata = identityServerConfiguration.RequireHttps;
                    o.SupportedTokens = SupportedTokens.Both;
                    o.ApiSecret = identityServerConfiguration.ApiSecret;
                });

                //todo - refactor naming..
                if (string.IsNullOrEmpty(identityServerConfiguration.CredentialsSigningCertificateLocation) || string.IsNullOrEmpty(identityServerConfiguration.CredentialsSigningCertificatePassword))
                {
                    identityServerBuilder.AddDeveloperSigningCredential();
                }
                else
                {
                    //todo - refactor so calls method?
                    var cert = new X509Certificate2(identityServerConfiguration.CredentialsSigningCertificateLocation, identityServerConfiguration.CredentialsSigningCertificatePassword);
                    identityServerBuilder.AddSigningCredential(cert);
                }
var whb = services.First(x => x.ServiceType == typeof(IWebHostBuilder));

这就代码触发了错误,是由于表达式条件不成立,导致First发生异常,这就简单了,我们修改Main函数,

把这句代码:

 var builder = new WebHostBuilder();

改成:

IWebHostBuilder builder = new WebHostBuilder();

这样,就解决了问题,API网关启动成功。

这样,使用Ocelot框架搭建API网关的工作已经完成,尝试通过访问API网关,来访问下游的服务。

此实例源码:https://gitee.com/lichaoqiang/RichCodeBox.git

欢迎大家一起研究探讨,开启你的微服务之路。