作者：依樂祝
原文地址：https://www.cnblogs.com/yilezhu/p/9852711.html

上篇文章給大家分享了如何集成我寫的一個Ocelot擴展插件把Ocelot的配置存儲到數據庫中。並沒有對實現原理進行相應的闡述。今天抽空把實現的原理給大家說道說道。明白原理後，大家就可以自行改寫進行擴展來滿足自身需要了！
再次感覺張隊的審稿，並給出的修改意見！

源碼解析過程

大家可以自行分析Ocelot的源碼，我通過分析ocelot的源碼得出，如果要實現重寫配置文件的方式，只需要寫一個類來實現IFileConfigurationRepository這個接口即可。

代碼如下：

 /// <summary>
    /// yilezhu
    /// 2018.10.22
    /// 實現從SQLSERVER數據庫中提取配置信息
    /// </summary>
    public class SqlServerFileConfigurationRepository : IFileConfigurationRepository
    {
        private readonly IOcelotCache<FileConfiguration> _cache;
        private readonly IOcelotLogger _logger;
        private readonly ConfigAuthLimitCacheOptions _option;
        public SqlServerFileConfigurationRepository(ConfigAuthLimitCacheOptions option, IOcelotCache<FileConfiguration> cache, IOcelotLoggerFactory loggerFactory)
        {
            _option = option;
            _cache = cache;
            _logger = loggerFactory.CreateLogger<SqlServerFileConfigurationRepository>();
        }

        public Task<Response> Set(FileConfiguration fileConfiguration)
        {
            _cache.AddAndDelete(_option.CachePrefix + "FileConfiguration", fileConfiguration, TimeSpan.FromSeconds(1800), "");
            return Task.FromResult((Response)new OkResponse());
        }

        /// <summary>
        /// 提取配置信息
        /// </summary>
        /// <returns></returns>
        public async Task<Response<FileConfiguration>> Get()
        {
            var config = _cache.Get(_option.CachePrefix + "FileConfiguration", "");

            if (config != null)
            {
                return new OkResponse<FileConfiguration>(config);
            }
            #region 提取配置信息
            var file = new FileConfiguration();
            string glbsql = "select top 1 * from OcelotGlobalConfiguration where IsDefault=1";
            //提取全局配置信息
            using (var connection = new SqlConnection(_option.DbConnectionStrings))
            {
                var result = await connection.QueryFirstOrDefaultAsync<OcelotGlobalConfiguration>(glbsql);
                if (result != null)
                {
                    var glb = new FileGlobalConfiguration();
                    glb.BaseUrl = result.BaseUrl;
                    glb.DownstreamScheme = result.DownstreamScheme;
                    glb.RequestIdKey = result.RequestIdKey;
                    if (!String.IsNullOrEmpty(result.HttpHandlerOptions))
                    {
                        glb.HttpHandlerOptions = result.HttpHandlerOptions.ToObject<FileHttpHandlerOptions>();
                    }
                    if (!String.IsNullOrEmpty(result.LoadBalancerOptions))
                    {
                        glb.LoadBalancerOptions = result.LoadBalancerOptions.ToObject<FileLoadBalancerOptions>();
                    }
                    if (!String.IsNullOrEmpty(result.QoSOptions))
                    {
                        glb.QoSOptions = result.QoSOptions.ToObject<FileQoSOptions>();
                    }
                    if (!String.IsNullOrEmpty(result.ServiceDiscoveryProvider))
                    {
                        glb.ServiceDiscoveryProvider = result.ServiceDiscoveryProvider.ToObject<FileServiceDiscoveryProvider>();
                    }
                    file.GlobalConfiguration = glb;

                    //提取路由信息

                    string routesql = "select * from OcelotReRoutes where OcelotGlobalConfigurationId=@OcelotGlobalConfigurationId and IsStatus=1";
                    var routeresult = (await connection.QueryAsync<OcelotReRoutes>(routesql, new { OcelotGlobalConfigurationId=result.Id })).AsList();
                    if (routeresult != null && routeresult.Count > 0)
                    {
                        var reroutelist = new List<FileReRoute>();
                        foreach (var model in routeresult)
                        {
                            var m = new FileReRoute();
                            if (!String.IsNullOrEmpty(model.AuthenticationOptions))
                            {
                                m.AuthenticationOptions = model.AuthenticationOptions.ToObject<FileAuthenticationOptions>();
                            }
                            if (!String.IsNullOrEmpty(model.CacheOptions))
                            {
                                m.FileCacheOptions = model.CacheOptions.ToObject<FileCacheOptions>();
                            }
                            if (!String.IsNullOrEmpty(model.DelegatingHandlers))
                            {
                                m.DelegatingHandlers = model.DelegatingHandlers.ToObject<List<string>>();
                            }
                            if (!String.IsNullOrEmpty(model.LoadBalancerOptions))
                            {
                                m.LoadBalancerOptions = model.LoadBalancerOptions.ToObject<FileLoadBalancerOptions>();
                            }
                            if (!String.IsNullOrEmpty(model.QoSOptions))
                            {
                                m.QoSOptions = model.QoSOptions.ToObject<FileQoSOptions>();
                            }
                            if (!String.IsNullOrEmpty(model.DownstreamHostAndPorts))
                            {
                                m.DownstreamHostAndPorts = model.DownstreamHostAndPorts.ToObject<List<FileHostAndPort>>();
                            }
                            //開始賦值
                            m.DownstreamPathTemplate = model.DownstreamPathTemplate;
                            m.DownstreamScheme = model.DownstreamScheme;
                            m.Key = model.Key;
                            m.Priority = model.Priority ?? 0;
                            m.RequestIdKey = model.RequestIdKey;
                            m.ServiceName = model.ServiceName;
                            m.Timeout = model.Timeout ?? 0;
                            m.UpstreamHost = model.UpstreamHost;
                            if (!String.IsNullOrEmpty(model.UpstreamHttpMethod))
                            {
                                m.UpstreamHttpMethod = model.UpstreamHttpMethod.ToObject<List<string>>();
                            }
                            m.UpstreamPathTemplate = model.UpstreamPathTemplate;
                            reroutelist.Add(m);
                        }
                        file.ReRoutes = reroutelist;
                    }
                }
                else
                {
                    throw new Exception("未監測到配置信息");
                }
            }
            #endregion
            if (file.ReRoutes == null || file.ReRoutes.Count == 0)
            {
                return new OkResponse<FileConfiguration>(null);
            }
            return new OkResponse<FileConfiguration>(file);
        }
    }
 

當然，既然我們已經重新實現了這個接口，那麽就得進行相應的DI了。這裏我們擴展下IOcelotBuilder方法，代碼如下,主要就是進行相應的服務的DI：

/// <summary>
    /// yilezhu
    /// 2018.10.22
    /// 基於Ocelot擴展的依賴註入
    /// </summary>
    public static class ServiceCollectionExtensions
    {
        /// <summary>
        /// 添加默認的註入方式，所有需要傳入的參數都是用默認值
        /// </summary>
        /// <param name="builder"></param>
        /// <returns></returns>
        public static IOcelotBuilder AddAuthLimitCache(this IOcelotBuilder builder, Action<ConfigAuthLimitCacheOptions> option)
        {
            builder.Services.Configure(option);
            builder.Services.AddSingleton(
                resolver => resolver.GetRequiredService<IOptions<ConfigAuthLimitCacheOptions>>().Value);
            #region 註入其他配置信息
            //重寫提取Ocelot配置信息，
            builder.Services.AddSingleton(DataBaseConfigurationProvider.Get);
            //builder.Services.AddHostedService<FileConfigurationPoller>();
            builder.Services.AddSingleton<IFileConfigurationRepository, SqlServerFileConfigurationRepository>();
            //註入自定義限流配置
            //註入認證信息
            #endregion
            return builder;
        }
    }
 

接下來就是重寫，OcelotBuild裏面配置文件的獲取方式了。這裏我選擇的是對IApplicationBuilder進行擴展，因為這樣方便做一些其他的事情，比如，重寫限流，集成自定義的驗證等等。具體代碼如下：

   /// <summary>
    /// yilezhu
    /// 2018.10.22
    /// 擴展IApplicationBuilder，新增use方法
    /// </summary>
    public static class OcelotMiddlewareExtensions
    {
        /// <summary>
        /// 擴展UseOcelot
        /// </summary>
        /// <param name="builder"></param>
        /// <returns></returns>
        public static async Task<IApplicationBuilder> UseAhphOcelot(this IApplicationBuilder builder)
        {
            await builder.UseAhphOcelot(new OcelotPipelineConfiguration());
            return builder;
        }

        /// <summary>
        /// 重寫Ocelot,帶參數
        /// </summary>
        /// <param name="builder"></param>
        /// <param name="pipelineConfiguration"></param>
        /// <returns></returns>
        public static async Task<IApplicationBuilder> UseAhphOcelot(this IApplicationBuilder builder, OcelotPipelineConfiguration pipelineConfiguration)
        {
            var configuration = await CreateConfiguration(builder);

            ConfigureDiagnosticListener(builder);

            return CreateOcelotPipeline(builder, pipelineConfiguration);
        }

        private static async Task<IInternalConfiguration> CreateConfiguration(IApplicationBuilder builder)
        {
            // make configuration from file system?
            // earlier user needed to add ocelot files in startup configuration stuff, asp.net will map it to this
            //var fileConfig = builder.ApplicationServices.GetService<IOptionsMonitor<FileConfiguration>>();
            var fileConfig = await builder.ApplicationServices.GetService<IFileConfigurationRepository>().Get();
            // now create the config
            var internalConfigCreator = builder.ApplicationServices.GetService<IInternalConfigurationCreator>();
            var internalConfig = await internalConfigCreator.Create(fileConfig.Data);
            //Configuration error, throw error message
            if (internalConfig.IsError)
            {
                ThrowToStopOcelotStarting(internalConfig);
            }

            // now save it in memory
            var internalConfigRepo = builder.ApplicationServices.GetService<IInternalConfigurationRepository>();
            internalConfigRepo.AddOrReplace(internalConfig.Data);

            //fileConfig.OnChange(async (config) =>
            //{
            //    var newInternalConfig = await internalConfigCreator.Create(config);
            //    internalConfigRepo.AddOrReplace(newInternalConfig.Data);
            //});

            var adminPath = builder.ApplicationServices.GetService<IAdministrationPath>();

            var configurations = builder.ApplicationServices.GetServices<OcelotMiddlewareConfigurationDelegate>();

            // Todo - this has just been added for consul so far...will there be an ordering problem in the future? Should refactor all config into this pattern?
            foreach (var configuration in configurations)
            {
                await configuration(builder);
            }

            if (AdministrationApiInUse(adminPath))
            {
                //We have to make sure the file config is set for the ocelot.env.json and ocelot.json so that if we pull it from the 
                //admin api it works...boy this is getting a spit spags boll.
                var fileConfigSetter = builder.ApplicationServices.GetService<IFileConfigurationSetter>();

                //  await SetFileConfig(fileConfigSetter, fileConfig.Data);
            }

            return GetOcelotConfigAndReturn(internalConfigRepo);
        }

        private static bool AdministrationApiInUse(IAdministrationPath adminPath)
        {
            return adminPath != null;
        }

        //private static async Task SetFileConfig(IFileConfigurationSetter fileConfigSetter, IOptionsMonitor<FileConfiguration> fileConfig)
        //{
        //    var response = await fileConfigSetter.Set(fileConfig.CurrentValue);

        //    if (IsError(response))
        //    {
        //        ThrowToStopOcelotStarting(response);
        //    }
        //}

        private static bool IsError(Response response)
        {
            return response == null || response.IsError;
        }

        private static IInternalConfiguration GetOcelotConfigAndReturn(IInternalConfigurationRepository provider)
        {
            var ocelotConfiguration = provider.Get();

            if (ocelotConfiguration?.Data == null || ocelotConfiguration.IsError)
            {
                ThrowToStopOcelotStarting(ocelotConfiguration);
            }

            return ocelotConfiguration.Data;
        }

        private static void ThrowToStopOcelotStarting(Response config)
        {
            throw new Exception($"Unable to start Ocelot, errors are: {string.Join(",", config.Errors.Select(x => x.ToString()))}");
        }

        private static IApplicationBuilder CreateOcelotPipeline(IApplicationBuilder builder, OcelotPipelineConfiguration pipelineConfiguration)
        {
            var pipelineBuilder = new OcelotPipelineBuilder(builder.ApplicationServices);

            //重寫自定義管道
            pipelineBuilder.BuildAhphOcelotPipeline(pipelineConfiguration);

            var firstDelegate = pipelineBuilder.Build();

            /*
            inject first delegate into first piece of asp.net middleware..maybe not like this
            then because we are updating the http context in ocelot it comes out correct for
            rest of asp.net..
            */

            builder.Properties["analysis.NextMiddlewareName"] = "TransitionToOcelotMiddleware";

            builder.Use(async (context, task) =>
            {
                var downstreamContext = new DownstreamContext(context);
                await firstDelegate.Invoke(downstreamContext);
            });

            return builder;
        }

        private static void ConfigureDiagnosticListener(IApplicationBuilder builder)
        {
            var env = builder.ApplicationServices.GetService<IHostingEnvironment>();
            var listener = builder.ApplicationServices.GetService<OcelotDiagnosticListener>();
            var diagnosticListener = builder.ApplicationServices.GetService<DiagnosticListener>();
            diagnosticListener.SubscribeWithAdapter(listener);
        }
    }

這其中最主要的代碼就是，重寫配置文件獲取這塊。我在下面進行了截圖，並圈出來了，大家自行查看吧。

代碼重寫好了。由於我們服務註冊時通過擴展IOcelotBuilder，所以，我們需要在ConfigureServices方法引入Ocelot服務的時候比Ocelot多寫一個方法，並傳入相關的配置信息，如下所示：

services.AddOcelot()//註入Ocelot服務
                    .AddAuthLimitCache(option=> {
                        option.DbConnectionStrings = "Server=.;Database=Ocelot;User ID=sa;Password=1;";
                    });

這裏的目的就是為了註入我們實現了IFileConfigurationRepository接口的SqlServerFileConfigurationRepository這個類。

接下來就是在管道中使用我們重寫的Ocelot服務了。如下所示，在Configure方法中按如下代碼進行使用：

app.UseAhphOcelot().Wait();

好了，以上就是實現的整個過程了。經過這麽一分析是不是覺得很簡單呢。當然具體為什麽按照上面處理就能夠從數據庫獲取配置了呢，這個還需要你分析了源碼後才能了解。我也只是給你引路，傳達我實現的思路。

源碼

https://github.com/yilezhu/Ocelot.ConfigAuthLimitCache

總結

今天抽空對上篇文章進行了補充說明，目的是給大家闡述下，配置文件存儲到數據庫中的實現過程及原理。讓你能夠根據自身需要來進行改寫來滿足你的業務需求。當然我也只是給你引路，具體為什麽這樣實現下就能夠成功呢？答案在Ocelot的源碼中。

如果你想了解更多Ocelot的定制相關的·內容可以看我一個朋友寫的系列博客，博客地址：https://www.cnblogs.com/jackcao/p/9928879.html 【.NET Core微服務實戰-統一身份認證】網關篇，這裏給你詳細介紹了如何進行自定義限流以及客戶端授權並重寫Ocelot緩存成Redis！有興趣的可以看下！

Ocelot簡易教程目錄

1. Ocelot簡易教程（一）之Ocelot是什麽
2. Ocelot簡易教程（二）之快速開始1
3. Ocelot簡易教程（二）之快速開始2
4. Ocelot簡易教程（三）之主要特性及路由詳解
5. Ocelot簡易教程（四）之請求聚合以及服務發現
6. Ocelot簡易教程（五）之集成IdentityServer認證以及授權
7. Ocelot簡易教程（六）之重寫配置文件存儲方式並優化響應數據
8. Ocelot簡易教程（七）之配置文件數據庫存儲插件源碼解析

Ocelot簡易教程（七）之配置文件數據庫存儲插件源碼解析