net core天马行空系列：移植Feign，结合Polly，实现回退，熔断，重试，超时，做最好用的声明式http服务调用端

系列目录

正文开始

hi，大家好，我就是高产似母猪的三合。距离上一篇文章，好像有点久了，我也不知道我都在干嘛，啊哈哈哈哈，今天这篇文章，从几个问题开始。

Feign是什么？

Feign它是一个声明式http服务调用端，做一个类比，如果把httpClient比作ado.net，那么feign就相当于ef/dapper。他是更顶层的封装，提供了更简单更友好的调用方式，更适合面向接口的编程习惯，通过接口+注解，就能实现http访问。因为微软爸爸认为网络请求是IO操作，用异步更为合适，所以feign只支持异步返回，即task<int>这种形式。

Feign用法

首先，注册服务的时候添加以下红线框出来的服务。

然后定义接口如下

最后注入使用

已经有webApiClient、refit了，为什么还要移植feign呢？

因为我觉得这两个组件还有一些不够完美的地方，比如没有和微软的DI更紧密的结合在一起，不是完全面向接口编程导致扩展性不佳，不支持回退，熔断，重试，超时等，于是我移植了java的feign项目，就有了这篇文章。

什么是回退、熔断、重试、超时？

回退：通俗来说就是备胎，如果方法调用报错了，比如调用的服务挂了，调用超时了等，就返回备胎里面的内容。定义回退类QueryEmployeeFallBack，该类也要实现IQueryEmployee接口

namespace Example.Feign
{
    public class QueryEmployeeFallBack : IQueryEmployee
    {
        public async Task<Employee> FindAsync([Param("")] string id, [Body] Employee user)
        {
            await Task.Delay(1000);
            return new Employee() {Name = "fallBack"};
        }

        public async Task<List<Employee>> GetEmployeeAsync(string url, int ab)
        {
            return await Task.FromResult(new List<Employee>(){new Employee(){Name = "fallBack"}});
        }

        public Task<int> GetEmployeeCountAsync()
        {
            return Task.FromResult(0);
        }
    }
}

重试：字面意思，就是方法调用报错了，则进行重试

超时：即给方法的执行限定时间，如果超出了这个时间，就默认为方法执行失败。

断路：如果执行方法出现错误，执行多次还是错误的话，就认为这个方法可能挂了，在设定的时间内就不会去调用这个方法，而是直接返回错误，实际场景比如调用的api服务可能因为访问量太大，快挂了，这时候我们试了3次还是报错后，在10s内就不会真正去访问这个api接口，而是直接报错，就可以避免给api接口造成更多压力。

移植的feign属于summerBoot项目的一部分，基于MIT协议开源，欢迎star，感兴趣的可以加Q群799648362

github地址：https://github.com/TripleView/SummerBoot

nuget搜索：SummerBoot

效果图

定义一个employee类用来测试

先新建一个webApi项目，写几个接口供http访问。

测试1.get请求，返回int类型，符合预期

测试2，带参数的get请求，返回List<Employee>，api接口正常接收到请求参数，调用返回正常，符合预期。

测试3.发送post请求，在body里添加内容，同时利用param注解改变参数名称，发送接收都正常，符合预期。

测试4，同时访问3个api接口，返回正常，符合预期

测试5，超时+回退，在feign客户端里定义超时时间为2000毫秒，即2s，api接口那边添加一行让线程停3s的代码，如果没超时应该返回1，但是超时了，日志里也显示超时，这时候就会进入回退，返回QueryEmployeeFallBack类对应方法的值0。

测试6，超时+重试+回退。定义重试3次，每次间隔1s，其余和测试5一致，日志显示，重试3次后进入回退，返回0，符合预期。

测试7，超时+重试+回退+熔断。关闭api接口，模拟服务挂了，定义重试3次，每次间隔1s，开启断路。日志提示重试3次，之间有进入熔断，返回0，符合预期。

源码解析，授人以渔

1.通过IL代码动态生成接口的实现类

核心类FeignProxyBuilder，这里要特别感谢苏州的黑洞视界同学，在IL代码方面给了我很大的帮助。这个类的核心思想，就是动态生成接口的实现类，生成的实现类只是一个空壳，他里面只有3个字段，第一个，List<object> 类型，用来存放调用方法时的实际参数，第二个，IServiceProvider，由构造函数传入，第三个，httpService类,这个类就是真正执行网络请求的类，也是由构造函数传入，这个实现类的作用就是当调用接口里的方法时，利用IL代码把传递进来的参数收集起来存放到list<object>的字段里，然后调用httpSerivce的方法，把参数集合，方法体信息methodInfo,还有IServiceProvider一起传入到httpService的代理方法里，httpService处理完毕后获得结果，利用IL代码清除掉list<object>字段里存放的参数，保证每次调用方法时，list<object>里都是空的，避免上次调用方法的参数没清空，影响到本次调用，最后返回方法调用结果。具体如何动态生成这个实现类，代码里都有详细注解了，同时IL处理时有个要义，调用实例前，一定都要加载类本身，即Ldarg_0。

public interface IProxyBuilder
    {
        Object Build(Type interfaceType,params object[] constructor);
        T Build<T>(params object[] constructor);
｝

namespace SummerBoot.Feign
{
    public interface IFeignProxyBuilder:IProxyBuilder
    {
    }
}

public class FeignProxyBuilder : IFeignProxyBuilder
    {
        public static Dictionary<string, MethodInfo> MethodsCache { get; set; } = new Dictionary<string, MethodInfo>();

        private Type targetType;

        private static ConcurrentDictionary<string, Type> TargetTypeCache { set; get; } =
            new ConcurrentDictionary<string, Type>();
        

        public object Build(Type interfaceType, params object[] constructor)
        {
            var cacheKey = interfaceType.FullName;
            var resultType = TargetTypeCache.GetOrAdd(cacheKey, (s)=> BuildTargetType(interfaceType, constructor));
            var result = Activator.CreateInstance(resultType, args: constructor);
            return result;
        }

        /// <summary>
        /// 动态生成接口的实现类
        /// </summary>
        /// <param name="interfaceType"></param>
        /// <param name="constructor"></param>
        /// <returns></returns>
        private Type BuildTargetType(Type interfaceType, params object[] constructor)
        {
            targetType = interfaceType;
            string assemblyName = targetType.Name + "ProxyAssembly";
            string moduleName = targetType.Name + "ProxyModule";
            string typeName = targetType.Name + "Proxy";

            AssemblyName assyName = new AssemblyName(assemblyName);
            AssemblyBuilder assyBuilder = AssemblyBuilder.DefineDynamicAssembly(assyName, AssemblyBuilderAccess.Run);
            ModuleBuilder modBuilder = assyBuilder.DefineDynamicModule(moduleName);

            //新类型的属性
            TypeAttributes newTypeAttribute = TypeAttributes.Class | TypeAttributes.Public;
            //父类型
            Type parentType;
            //要实现的接口
            Type[] interfaceTypes;

            if (targetType.IsInterface)
            {
                parentType = typeof(object);
                interfaceTypes = new Type[] { targetType };
            }
            else
            {
                parentType = targetType;
                interfaceTypes = Type.EmptyTypes;
            }
            //得到类型生成器            
            TypeBuilder typeBuilder = modBuilder.DefineType(typeName, newTypeAttribute, parentType, interfaceTypes);

            //定义一个字段存放httpService
            var httpType = typeof(HttpService);
            FieldBuilder httpServiceField = typeBuilder.DefineField("httpService",
                httpType, FieldAttributes.Public);
            
            //定义一个字段存放IServiceProvider
            var iServiceProviderType = typeof(IServiceProvider);
            FieldBuilder serviceProviderField = typeBuilder.DefineField("iServiceProvider",
                iServiceProviderType, FieldAttributes.Public);

            //定义一个集合存放参数集合
            FieldBuilder paramterArrField = typeBuilder.DefineField("paramterArr",
                typeof(List<object>), FieldAttributes.Public);
            //创建构造函数
            ConstructorBuilder constructorBuilder =
                typeBuilder.DefineConstructor(MethodAttributes.Public, CallingConventions.Standard, new Type[] { httpType, iServiceProviderType });

            //il创建构造函数，对httpService和IServiceProvider两个字段进行赋值，同时初始化存放参数的集合
            ILGenerator ilgCtor = constructorBuilder.GetILGenerator();
            ilgCtor.Emit(OpCodes.Ldarg_0); //加载当前类
            ilgCtor.Emit(OpCodes.Ldarg_1);
            ilgCtor.Emit(OpCodes.Stfld, httpServiceField);

            ilgCtor.Emit(OpCodes.Ldarg_0); //加载当前类
            ilgCtor.Emit(OpCodes.Ldarg_2);
            ilgCtor.Emit(OpCodes.Stfld, serviceProviderField);

            ilgCtor.Emit(OpCodes.Ldarg_0); //加载当前类
            ilgCtor.Emit(OpCodes.Newobj, typeof(List<object>).GetConstructors().First());
            ilgCtor.Emit(OpCodes.Stfld, paramterArrField);
            ilgCtor.Emit(OpCodes.Ret); //返回

            MethodInfo[] targetMethods = targetType.GetMethods();

            foreach (MethodInfo targetMethod in targetMethods)
            {
                //只挑出virtual的方法
                if (targetMethod.IsVirtual)
                {
                    //缓存接口的方法体，便于后续将方法体传递给httpService
                    string methodKey = Guid.NewGuid().ToString();
                    MethodsCache[methodKey] = targetMethod;

                    //得到方法的各个参数的类型和参数
                    var paramInfo = targetMethod.GetParameters();
                    var parameterType = paramInfo.Select(it => it.ParameterType).ToArray();
                    var returnType = targetMethod.ReturnType;
                    //方法返回值只能是task，即只支持异步，因为http操作是io操作
                    if (!typeof(Task).IsAssignableFrom(returnType)) throw new Exception("return type must be task<>");
                    var underType = returnType.IsGenericType ? returnType.GetGenericArguments().First() : returnType;

                    //通过emit生成方法体
                    MethodBuilder methodBuilder = typeBuilder.DefineMethod(targetMethod.Name, MethodAttributes.Public | MethodAttributes.Virtual, targetMethod.ReturnType, parameterType);
                    ILGenerator ilGen = methodBuilder.GetILGenerator();

                    MethodInfo executeMethod = null;
                    var methodTmp = httpType.GetMethod("ExecuteAsync");

                    if (methodTmp == null) throw new Exception("找不到执行方法");
                    executeMethod = methodTmp.IsGenericMethod ? methodTmp.MakeGenericMethod(underType) : methodTmp;

                    // 栈底放这玩意，加载字段前要加载类实例，即Ldarg_0
                    ilGen.Emit(OpCodes.Ldarg_0);
                    ilGen.Emit(OpCodes.Ldfld, httpServiceField);
                    
                    //把所有参数都放到list<object>里
                    ilGen.Emit(OpCodes.Ldarg_0);
                    ilGen.Emit(OpCodes.Ldfld, paramterArrField);
                    for (int i = 0; i < parameterType.Length; i++)
                    {
                        ilGen.Emit(OpCodes.Dup);
                        ilGen.Emit(OpCodes.Ldarg_S, i + 1);
                        if (parameterType[i].IsValueType)
                        {
                            ilGen.Emit(OpCodes.Box, parameterType[i]);
                        }
                        ilGen.Emit(OpCodes.Callvirt, typeof(List<object>).GetMethod("Add"));
                    }

                    // 当前栈[httpServiceField paramterArrField]
                    //从缓存里取出方法体
                    ilGen.Emit(OpCodes.Call,
                        typeof(FeignProxyBuilder).GetMethod("get_MethodsCache", BindingFlags.Static | BindingFlags.Public));
                    ilGen.Emit(OpCodes.Ldstr, methodKey);
                    ilGen.Emit(OpCodes.Call, typeof(Dictionary<string, MethodInfo>).GetMethod("get_Item"));

                    ilGen.Emit(OpCodes.Ldarg_0);
                    ilGen.Emit(OpCodes.Ldfld, serviceProviderField);

                    ilGen.Emit(OpCodes.Callvirt, executeMethod);
                    //清空list里的参数
                    ilGen.Emit(OpCodes.Ldarg_0);
                    ilGen.Emit(OpCodes.Ldfld, paramterArrField);
                    ilGen.Emit(OpCodes.Callvirt, typeof(List<object>).GetMethod("Clear"));
                    // pop the stack if return void
                    if (targetMethod.ReturnType == typeof(void))
                    {
                        ilGen.Emit(OpCodes.Pop);
                    }

                    // complete
                    ilGen.Emit(OpCodes.Ret);
                    typeBuilder.DefineMethodOverride(methodBuilder, targetMethod);
                }
            }

            var resultType = typeBuilder.CreateTypeInfo().AsType();
            return resultType;
        }

        public T Build<T>(params object[] constructor)
        {
            return (T)this.Build(typeof(T), constructor);
        }
    }

2.完全面向接口设计的feign源码

feign中的接口

1.IClient接口，这个接口代表的就是实际执行网络请求的类，他的默认实现类DefaultFeignClient 基于httpClient，也可以自己实现这个接口，换成其他网络请求客户端。在feign框架调用iclient之前，会把所有请求信息封装到requestTemplate里，iclient执行完毕后，也需要把所有返回信息封装到responseTemplate里，利用这两个类，解耦了feign框架与具体iclient实现类。

namespace SummerBoot.Feign
{
    /// <summary>
    /// 实际执行http请求的客户端
    /// </summary>
    public interface IClient
    {
        Task<ResponseTemplate> ExecuteAsync(RequestTemplate requestTemplate, CancellationToken cancellationToken);
        /// <summary>
        /// 默认的IClient类，内部采用httpClient
        /// </summary>
        public class DefaultFeignClient : IClient
        {
            private IHttpClientFactory HttpClientFactory { get; }
            public DefaultFeignClient(IHttpClientFactory iHttpClientFactory)
            {
                HttpClientFactory = iHttpClientFactory;
            }

            public async Task<ResponseTemplate> ExecuteAsync(RequestTemplate requestTemplate, CancellationToken cancellationToken)
            {
                var httpClient = HttpClientFactory.CreateClient();

                var httpRequest = new HttpRequestMessage(requestTemplate.HttpMethod, requestTemplate.Url);

                if (requestTemplate.HttpMethod == HttpMethod.Post)
                {
                    httpRequest.Content = new StringContent(requestTemplate.Body);
                }

                //处理header
                foreach (var requestTemplateHeader in requestTemplate.Headers)
                {
                    var uppperKey = requestTemplateHeader.Key.ToUpper();

                    var key = uppperKey.Replace("-", "");
                    //判断普通标头
                    if (HttpHeaderSupport.RequestHeaders.Contains(key))
                    {
                        httpRequest.Headers.Remove(requestTemplateHeader.Key);
                        httpRequest.Headers.Add(requestTemplateHeader.Key, requestTemplateHeader.Value);
                    }
                    //判断body标头
                    else if (HttpHeaderSupport.ContentHeaders.Contains(key))
                    {
                        httpRequest.Content.Headers.Remove(requestTemplateHeader.Key);
                        httpRequest.Content.Headers.Add(requestTemplateHeader.Key, requestTemplateHeader.Value);
                    }
                    //自定义标头
                    else
                    {
                        httpRequest.Headers.TryAddWithoutValidation(requestTemplateHeader.Key,
                            requestTemplateHeader.Value);
                    }
                }

                var httpResponse = await httpClient.SendAsync(httpRequest, cancellationToken);

                //把httpResponseMessage转化为responseTemplate
                var result = await ConvertResponseAsync(httpResponse);

                return result;
            }

            /// <summary>
            /// 把httpResponseMessage转化为responseTemplate
            /// </summary>
            /// <param name="responseMessage"></param>
            /// <returns></returns>
            private async Task<ResponseTemplate> ConvertResponseAsync(HttpResponseMessage responseMessage)
            {
                var responseTemplate = new ResponseTemplate
                {
                    HttpStatusCode = responseMessage.StatusCode
                };

                var headers = responseMessage.Headers;
                foreach (var httpResponseHeader in headers)
                {
                    responseTemplate.Headers.Add(httpResponseHeader);
                }

                var stream = new MemoryStream();
                await responseMessage.Content.CopyToAsync(stream);
                stream.Seek(0, SeekOrigin.Begin);
                responseTemplate.Body = stream;
                return responseTemplate;
            }
        }
    }
}

2.IFeignEncoder接口，这个接口的作用是定义序列化器，比如在post请求中，定义如何序列化参数然后放到body里，默认实现类DefaultEncoder 基于json，也可以实现该接口，换成其他种序列化方式。

namespace SummerBoot.Feign
{
    /// <summary>
    /// 序列化接口
    /// </summary>
    public interface IFeignEncoder
    {
        void Encoder(object obj, RequestTemplate requestTemplate);
        /// <summary>
        /// 默认的序列化器
        /// </summary>
        public class DefaultEncoder : IFeignEncoder
        {
            public void Encoder(object obj, RequestTemplate requestTemplate)
            {
                var objStr = JsonConvert.SerializeObject(obj);
                requestTemplate.Body = objStr;
            }
        }
    }
}

3.IFeignDecoder接口，这个接口的作用是定义反序列化器，作用是将网络请求成功后收到的信息反序列化成结果，默认实现类DefaultDecoder基于json，也可以实现该接口，换成其他种反序列化方式

namespace SummerBoot.Feign
{
    /// <summary>
    /// 反序列化接口
    /// </summary>
    public interface IFeignDecoder
    {
        object Decoder(ResponseTemplate responseTemplate, Type type);

        T Decoder<T>(ResponseTemplate responseTemplate);

        /// <summary>
        /// 默认的反序列化器
        /// </summary>
        public class DefaultDecoder : IFeignDecoder
        {
            public object Decoder(ResponseTemplate responseTemplate, Type type)
            {
                if (responseTemplate.HttpStatusCode == HttpStatusCode.NotFound ||
                    responseTemplate.HttpStatusCode == HttpStatusCode.NoContent)
                {
                    return type.GetDefaultValue();
                }

                if (responseTemplate.Body == null) return null;
                var body = responseTemplate.Body;
                var str = body.ConvertToString();
                return JsonConvert.DeserializeObject(str, type);
            }

            public T Decoder<T>(ResponseTemplate responseTemplate)
            {
                return (T)this.Decoder(responseTemplate, typeof(T));
            }
        }
    }
}

IRequestInterceptor接口，这个接口的作用是在网络请求前，拦截该请求，可以做一些自定义操作，比如添加授权，该接口没有默认实现类，如果有拦截需求可以实现该接口并注册到DI容器即可拦截。

namespace SummerBoot.Feign
{
    public interface IRequestInterceptor
    {
        void Apply(RequestTemplate requestTemplate);
    }
}

feign在添加服务的时候都是采用尝试注册，所以如果有自定义的接口，在添加feign服务之前注册到DI容器里，即可替换feign的默认实现。

类似这样

feign中的注解

1.FeignClientAttribute，这个注解只能用在接口上，添加了这个注解的接口都会被当成feign客户端注册到DI容器里，主要有服务名称，url地址，回退类，路径等参数。

namespace SummerBoot.Feign
{
    [AttributeUsage(AttributeTargets.Interface)]
    public class FeignClientAttribute:Attribute
    {
        /// <summary>
        /// 服务名称
        /// </summary>
        public string Name { get; }
        /// <summary>
        /// url地址
        /// </summary>
        public string Url { get; }
        /// <summary>
        /// 回退类
        /// </summary>
        public Type FallBack { get; }
        public Type Configuration { get; }
        public bool Decode404 { get; }
        public string Qualifier { get; }
        /// <summary>
        /// 路径
        /// </summary>
        public string Path { get; }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="name">服务名称</param>
        /// <param name="url">url地址</param>
        /// <param name="fallBack">回退类</param>
        /// <param name="configuration"></param>
        /// <param name="decode404"></param>
        /// <param name="qualifier"></param>
        /// <param name="path">路径</param>
        public FeignClientAttribute(string name,string url="",Type fallBack=null,Type configuration=null,bool decode404=false,string qualifier="",string path="")
        {
            Name = name;
            Url = url;
            FallBack = fallBack;
            Configuration = configuration;
            Decode404 = decode404;
            Qualifier = qualifier;
            Path = path;
        }
    }
}

2.HeadersAttribute注解，用来添加请求头，params类型，可以添加N个请求头

namespace SummerBoot.Feign
{
    [AttributeUsage(AttributeTargets.Method)]
    public class HeadersAttribute:Attribute
    {
        public string[] Param { get; }
        public HeadersAttribute(params  string[] param)
        {
            Param = param;
        }
    }
}

3.GetMappingAttribute和PostMappingAttribute，get请求和post请求的注解，只有一个value的参数，代表路径。

 public class PostMappingAttribute : HttpMappingAttribute
    {
        public PostMappingAttribute(string value):base(value)
        {
        }
    }

namespace SummerBoot.Feign
{
    public class GetMappingAttribute:HttpMappingAttribute
    {
        public GetMappingAttribute(string value):base(value)
        {
            
        }
    }
}

4.BodyAttribute，在post请求中，给class类型的参数添加，即代表将该参数添加到请求的body里。

namespace SummerBoot.Feign
{
    [AttributeUsage(AttributeTargets.Parameter)]
    public class BodyAttribute:Attribute
    {

    }
}

5.ParamAttribute，参数注解，主要是用来实现重命名参数的效果，比如接口方法中这个参数名叫employee，但是url中是user，那么利用这个注解即可重命名为user，[param("user")]即可。

namespace SummerBoot.Feign
{
    [AttributeUsage(AttributeTargets.Parameter)]
    public class ParamAttribute : Attribute
    {
        public string Value { get; }

        public ParamAttribute(string value = "")
        {
            Value = value;
        }
    }
}

6.PollyAttribute注解，主要定义了重试，超时，断路的一些策略。

namespace SummerBoot.Core
{
    [AttributeUsage(AttributeTargets.Interface)]
    public class PollyAttribute:Attribute
    {
        public int Retry { get; }
        public int RetryInterval { get; }
        public bool OpenCircuitBreaker { get; }
        public int ExceptionsAllowedBeforeBreaking { get; }

        public int DurationOfBreak { get; }
        public int Timeout { get; }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="retry">重试次数</param>
        /// <param name="retryInterval">重试间隔，单位毫秒</param>
        /// <param name="openCircuitBreaker">是否开启断路</param>
        /// <param name="exceptionsAllowedBeforeBreaking">错误几次进入断路</param>
        /// <param name="durationOfBreak">断路时间</param>
        /// <param name="timeout">超时时间，单位毫秒</param>
        public PollyAttribute(int retry=0,int retryInterval=500,bool openCircuitBreaker=false,int exceptionsAllowedBeforeBreaking = 3, int durationOfBreak = 1000, int timeout=0)
        {
            Retry = retry;
            RetryInterval = retryInterval;
            OpenCircuitBreaker = openCircuitBreaker;
            ExceptionsAllowedBeforeBreaking = exceptionsAllowedBeforeBreaking;
            DurationOfBreak = durationOfBreak;
            Timeout = timeout;
        }
    }
}

核心类FeignAspectSupport，这个类就是一个胶水类，负责解析注解，获得各种接口实现类，然后进行方法调用，获取最后结果，主要地方都有注释。

namespace SummerBoot.Feign
{
    public class FeignAspectSupport
    {
        private IServiceProvider _serviceProvider;

        public async Task<T> BaseExecuteAsync<T>(MethodInfo method, object[] args, IServiceProvider serviceProvider)
        {
            _serviceProvider = serviceProvider;
            //获得具体的client客户端
            var feignClient = serviceProvider.GetService<IClient>();
            //序列化器与反序列化器
            var encoder = serviceProvider.GetService<IFeignEncoder>();
            var decoder = serviceProvider.GetService<IFeignDecoder>();

            //读取feignClientAttribute里的信息；
            //接口类型
            var interfaceType = method.DeclaringType;
            if (interfaceType == null) throw new Exception(nameof(interfaceType));
            var feignClientAttribute = interfaceType.GetCustomAttribute<FeignClientAttribute>();
            var url = feignClientAttribute.Url;
            var path = feignClientAttribute.Path;
            var path2 = string.Empty;
            var clientName = feignClientAttribute.Name;
            var requestPath = url + path;
            var requestTemplate = new RequestTemplate();

            //获得请求拦截器
            var requestInterceptor = serviceProvider.GetService<IRequestInterceptor>();
            
            //处理请求头逻辑
            ProcessHeaders(method, requestTemplate);

            //处理get逻辑
            var getMappingAttribute = method.GetCustomAttribute<GetMappingAttribute>();
            if (getMappingAttribute != null)
            {
                path2 = getMappingAttribute.Value;
                requestTemplate.HttpMethod = HttpMethod.Get;
            }

            //处理post逻辑
            var postMappingAttribute = method.GetCustomAttribute<PostMappingAttribute>();
            if (postMappingAttribute != null)
            {
                path2 = postMappingAttribute.Value;
                requestTemplate.HttpMethod = HttpMethod.Post;
            }

            var urlTemp = (requestPath + path2).ToLower();
            
            requestTemplate.Url = GetUrl(urlTemp);

            //处理参数,因为有些参数需要拼接到url里，所以要在url处理完毕后才能处理参数
            ProcessParameter(method, args, requestTemplate, encoder);

            //如果存在拦截器，则进行拦截
            if(requestInterceptor!=null) requestInterceptor.Apply(requestTemplate);

            var responseTemplate = await feignClient.ExecuteAsync(requestTemplate, new CancellationToken());
           
            //判断方法返回值是否为异步类型
            var isAsyncReturnType = method.ReturnType.IsAsyncType();
            //返回类型
            var returnType = isAsyncReturnType ? method.ReturnType.GenericTypeArguments.First() : method.ReturnType;

            var resultTmp = (T)decoder.Decoder(responseTemplate, returnType);

            return resultTmp;
        }

        private string GetUrl(string urlTemp)
        {
            Func<string,string> func = (string s) =>
            {
                s = s.Replace("//", "/");
                s = s.Replace("///", "/");
                s = "http://" + s;
                return s;
            };

            if (urlTemp.Length < 8)
            {
                return func(urlTemp);
            }
            
            var isHttp = urlTemp.Substring(0, 7) == "http://";
            var isHttps = urlTemp.Substring(0, 8) == "https://";
            if (!isHttp && !isHttps)
            {
                return func(urlTemp);
            }

            if (isHttp)
            {
                urlTemp = urlTemp.Substring(7, urlTemp.Length - 7);
                return func(urlTemp);
            }

            if (isHttps)
            {
                urlTemp=urlTemp.Substring(8, urlTemp.Length - 8);
                urlTemp = urlTemp.Replace("//", "/");
                urlTemp = urlTemp.Replace("///", "/");
                urlTemp = "https://" + urlTemp;
            }

            return urlTemp;
        }

        /// <summary>
        /// 处理请求头逻辑
        /// </summary>
        /// <param name="method"></param>
        /// <param name="requestTemplate"></param>
        private void ProcessHeaders(MethodInfo method, RequestTemplate requestTemplate)
        {
            var headersAttribute = method.GetCustomAttribute<HeadersAttribute>();
            if (headersAttribute != null)
            {
                var headerParams = headersAttribute.Param;
                foreach (var headerParam in headerParams)
                {
                    if (headerParam.HasIndexOf(':'))
                    {
                        var headerParamArr = headerParam.Split(":");
                        var key = headerParamArr[0].Trim();
                        var keyValue = headerParamArr[1];
                        var hasHeaderKey = requestTemplate.Headers.TryGetValue(key, out var keyList);
                        if (!hasHeaderKey) keyList = new List<string>();
                        keyList.Add(keyValue.Trim());
                        if (!hasHeaderKey) requestTemplate.Headers.Add(key, keyList);
                    }
                }
            }
        }

        /// <summary>
        /// 处理参数
        /// </summary>
        private void ProcessParameter(MethodInfo method, object[] args, RequestTemplate requestTemplate, IFeignEncoder encoder)
        {
            var parameterInfos = method.GetParameters();
            //所有参数里，只能有一个body的注解
            var hasBodyAttribute = false;
            //参数集合
            var parameters = new Dictionary<string, string>();
            //url
            var url = requestTemplate.Url;

            for (var i = 0; i < parameterInfos.Length; i++)
            {
                var arg = args[i];
                var parameterInfo = parameterInfos[i];
                var parameterType = parameterInfos[i].ParameterType;
                var paramAttribute = parameterInfo.GetCustomAttribute<ParamAttribute>();
                var bodyAttribute = parameterInfo.GetCustomAttribute<BodyAttribute>();
                var parameterName = parameterInfos[i].Name;

                if (paramAttribute != null && bodyAttribute != null)
                {
                    throw new Exception(parameterType.Name + "can not accept parameterAttrite and bodyAttribute");
                }

                if (hasBodyAttribute) throw new Exception("bodyAttribute just only one");
                if (bodyAttribute != null) hasBodyAttribute = true;

                var parameterTypeIsString = parameterType.IsString();

                //处理param类型
                if ((parameterTypeIsString || parameterType.IsValueType) && bodyAttribute == null)
                {
                    parameterName = paramAttribute != null? paramAttribute.Value.GetValueOrDefault(parameterName):parameterName;
                    parameters.Add(parameterName, arg.ToString());
                }

                //处理body类型
                if (!parameterTypeIsString && parameterType.IsClass && bodyAttribute != null)
                {
                    encoder.Encoder(args[i], requestTemplate);
                }
            }

            var strParam = string.Join("&", parameters.Select(o => o.Key + "=" + o.Value));
            if (strParam.HasText()) url = string.Concat(url, '?', strParam);
            requestTemplate.Url = url;
        }
    }
}

View Code

核心类httpService，这个类是FeignAspectSupport的子类，主要是负责解析polly的各种策略，然后组合成polly的policy，最后调用FeignAspectSupport的方法，实现重试，断路，超时等

namespace SummerBoot.Feign
{
    public class HttpService : FeignAspectSupport
    {

        public async Task<T> ExecuteAsync<T>(List<object> originArgs, MethodInfo method, IServiceProvider serviceProvider)
        {
            var args = new List<object>();
            originArgs.ForEach(it => args.Add(it));

            var interfaceType = method.DeclaringType;
            if (interfaceType == null) throw new Exception(nameof(interfaceType));
            var feignClientAttribute = interfaceType.GetCustomAttribute<FeignClientAttribute>();
            var name = feignClientAttribute.Name;
            var fallBack = feignClientAttribute.FallBack;
            object interfaceTarget;
            //处理熔断重试超时逻辑
            IAsyncPolicy<T> policy = Policy.NoOpAsync<T>();
            var logFactory = serviceProvider.GetService<ILoggerFactory>();
            var log = logFactory.CreateLogger<HttpService>();

            if (fallBack != null)
            {
                policy = policy.WrapAsync(Policy<T>.Handle<Exception>()
                      .FallbackAsync<T>(async (x) =>
                      {
                          interfaceTarget = serviceProvider.GetServiceByName(interfaceType.Name + "FallBack", interfaceType);
                          var fallBackMethod = interfaceTarget.GetType().GetMethods().First(it => it.ReturnType == method.ReturnType && it.Name == method.Name);
                          var fallBackTask = fallBackMethod.Invoke(interfaceTarget, args.ToArray()) as Task<T>;
                          if (fallBackTask == null) throw new Exception("fallBack method ReturnValue error");
                          return await fallBackTask;
                      }));
            }

            var pollyAttribute = interfaceType.GetCustomAttribute<PollyAttribute>();

            if (pollyAttribute != null)
            {
                if (pollyAttribute.Retry > 0)
                {
                    policy = policy.WrapAsync(Policy.Handle<Exception>().WaitAndRetryAsync(pollyAttribute.Retry, i => TimeSpan.FromMilliseconds(pollyAttribute.RetryInterval), (
                        (exception, retryCount, context) =>
                        {
                            log.LogError($"feign客户端{name}：开始第 " + retryCount + "次重试,当前时间:" + DateTime.Now);
                        })));
                }

                if (pollyAttribute.Timeout > 0)
                {
                    policy = policy.WrapAsync(Policy.TimeoutAsync(() => TimeSpan.FromMilliseconds(pollyAttribute.Timeout), Polly.Timeout.TimeoutStrategy.Pessimistic, (
                        (context, span, arg3, arg4) =>
                        {
                            log.LogError($"feign客户端{name}：超时提醒,当前时间:" + DateTime.Now);
                            return Task.CompletedTask;
                        })));
                }

                if (pollyAttribute.OpenCircuitBreaker)
                {
                    policy = policy.WrapAsync(Policy.Handle<Exception>().CircuitBreakerAsync(pollyAttribute.ExceptionsAllowedBeforeBreaking, TimeSpan.FromMilliseconds(pollyAttribute.DurationOfBreak), (
                    //policy = policy.WrapAsync(Policy.Handle<Exception>().CircuitBreakerAsync(1, TimeSpan.FromMilliseconds(1500), (
                        (exception, span, arg3) =>
                        {
                            log.LogError($"feign客户端{name}：熔断: {span.TotalMilliseconds } ms, 异常: " + exception.Message + DateTime.Now);
                        }), (context =>
                    {
                        log.LogError("feign客户端{name}：熔断器关闭了" + DateTime.Now);
                    }),
                        (() => { log.LogError("feign客户端{name}：熔断时间到，进入半开状态" + DateTime.Now); })));
                }

                return await policy.ExecuteAsync(async () => await base.BaseExecuteAsync<T>(method, args.ToArray(), serviceProvider));
            }

            return await base.BaseExecuteAsync<T>(method, args.ToArray(), serviceProvider);


        }
    }
}