互联网分布式服务设计 - 接口基础协议

一、目录大纲

• 接口基础协议
• 接口一致性模式（同步&异步）
• 接口授权&签名
• 接口限流&熔断模式
• 接口性能优化技巧

二、接口基础协议

       内网服务接口，通用协议定义在HttpGet、HttpPost协议两种。对于接口定义，我们通常采用基于Restful协议定义约束，提供给我们的业务方调用。

       通用的请求类，我们习惯性分为两种：带分页和不带分页的请求，带分页的请求，我们一般定义如下数据结构

    public class RequestBase
    {
        public RequestBase();

        public bool allow_paging { get; set; }
        public int page_index { get; set; }
        public int page_size { get; set; }
        public string order_by { get; set; }
        public bool if_asc { get; set; }
        public int skip { get; }
    }

        业界对于接口协议返回数据结构，一般定义如下：

public class ResponseBase
{
    public bool success { get; set; }
    public string code { get; set; }
    public string errorMsg { get; set; }
    public T data { get; set; }
}

         对于文件流操作上传HttpPost的接口，例如采用Form表单提交，并上传图片流

        /// 

        /// 使用Post方法获取字符串结果
        /// 
        /// 
        /// Post表单内容
        /// 
        /// 默认20秒
        /// 响应内容的编码类型（默认utf-8）
        /// 
        public static string PostForm(string url, List formItems, CookieContainer cookieContainer = null, string refererUrl = null, Encoding encoding = null, int timeOut = 20000)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            #region 初始化请求对象
            request.Method = "POST";
            request.Timeout = timeOut;
            request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8";
            request.KeepAlive = true;
            request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.57 Safari/537.36";
            if (!string.IsNullOrEmpty(refererUrl))
                request.Referer = refererUrl;
            if (cookieContainer != null)
                request.CookieContainer = cookieContainer;

            if (url.StartsWith("https"))
            {
                ServicePointManager.ServerCertificateValidationCallback = new System.Net.Security.RemoteCertificateValidationCallback((object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors) =>
                {
                    return true;
                });
            }

            #endregion

            string boundary = "----" + DateTime.Now.Ticks.ToString("x");//分隔符
            request.ContentType = string.Format("multipart/form-data; boundary={0}", boundary);
            //请求流
            var postStream = new MemoryStream();
            #region 处理Form表单请求内容
            //是否用Form上传文件
            var formUploadFile = formItems != null && formItems.Count > 0;
            if (formUploadFile)
            {
                //文件数据模板
                string fileFormdataTemplate =
                    "\r\n--" + boundary +
                    "\r\nContent-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"" +
                    "\r\nContent-Type: application/octet-stream" +
                    "\r\n\r\n";
                //文本数据模板
                string dataFormdataTemplate =
                    "\r\n--" + boundary +
                    "\r\nContent-Disposition: form-data; name=\"{0}\"" +
                    "\r\n\r\n{1}";
                foreach (var item in formItems)
                {
                    string formdata = null;
                    //上传文件
                    formdata = string.Format(
                        fileFormdataTemplate,
                        item.Key, //表单键
                        item.FileName);

                    //统一处理
                    byte[] formdataBytes = null;
                    //第一行不需要换行
                    if (postStream.Length == 0)
                        formdataBytes = Encoding.UTF8.GetBytes(formdata.Substring(2, formdata.Length - 2));
                    else
                        formdataBytes = Encoding.UTF8.GetBytes(formdata);
                    postStream.Write(formdataBytes, 0, formdataBytes.Length);

                    //写入文件内容
                    if (item.FileContent != null && item.FileContent.Length > 0)
                    {
                        postStream.Write(item.FileContent, 0, item.FileContent.Length);
                    }
                }
                //结尾
                var footer = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");
                postStream.Write(footer, 0, footer.Length);

            }
            else
            {
                request.ContentType = "application/x-www-form-urlencoded";
            }
            #endregion

            request.ContentLength = postStream.Length;

            #region 输入二进制流
            if (postStream != null)
            {
                postStream.Position = 0;
                //直接写入流
                Stream requestStream = request.GetRequestStream();

                byte[] buffer = new byte[1024];
                int bytesRead = 0;
                while ((bytesRead = postStream.Read(buffer, 0, buffer.Length)) != 0)
                {
                    requestStream.Write(buffer, 0, bytesRead);
                }

                ////debug
                //postStream.Seek(0, SeekOrigin.Begin);
                //StreamReader sr = new StreamReader(postStream);
                //var postStr = sr.ReadToEnd();
                postStream.Close();//关闭文件访问
            }
            #endregion

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            if (cookieContainer != null)
            {
                response.Cookies = cookieContainer.GetCookies(response.ResponseUri);
            }

            using (Stream responseStream = response.GetResponseStream())
            {
                using (StreamReader myStreamReader = new StreamReader(responseStream, encoding ?? Encoding.UTF8))
                {
                    string retString = myStreamReader.ReadToEnd();
                    return retString;
                }
            }
        }

 /// 

    /// 表单数据项
    /// 
    public class FormItemModel
    {
        /// 

        /// 表单键，request["key"]
        /// 
        public string Key { set; get; }
        /// 

        /// 表单值,上传文件时忽略，request["key"].value
        /// 
        public string Value { set; get; }

        /// 

        /// 上传的文件名
        /// 
        public string FileName { set; get; }
        /// 

        /// 上传的文件内容
        /// 
        public byte[] FileContent { set; get; }
    }

调用示例：

     var content = PostForm(reqUrl, new List()
            {
                new FormItemModel()
                {
                    Key = "image_fn",
                    Value = "",
                    FileName = "1.jpg",
                    FileContent = request.image_fn
                }
            });

三、接口一致性模式（同步&异步）

参考文章 https://blog.csdn.net/qq_42192693/article/details/120391725

接口一致性模式包括

1、纯DB模式交互: 尽量控制DB拆分原则，在同一数据库实例下，通过DB的ACID特性保证事务一致性

2、DB+分布式服务组合：

     无中心化的微服务架构进行有效的拆分实现敏捷开发和自动化部署，并且在海量用户请求下，提高微服务架构细粒度的水平伸缩能力。

细粒度的水平伸缩能力。 

四、接口授权&签名

五、接口限流&熔断模式

六、接口性能优化技巧