保存呼叫WCF/Web Service的完整通聯記錄

2010-10-21 09:44 AM

在系統整合時，難免會涉及廠商或其他系統提供的WCF/Web Service。

要呼叫別人寫的WCF/WS，技術層面一點都不難! 在專案中Add Service Reference / Add Web Reference，Visual Studio便會打理剩下的瑣碎細節，自動幫你建立好Proxy物件，使用對方的服務就跟呼叫自己專案的元件一樣方便。

不過，老江湖都知道，呼叫別人服務的凶險所在並不在技術! 跨系統整合最怕的就是 -- 發生問題時各系統互踢皮球，堅稱問題不在自己身上，複雜的案情讓李組長不只要皺眉，就算把臉糾成包子也無解；網頁取存過程有Log可查，但呼叫其他系統的Web Service，相關Log可能遠在天邊廠商的主機上，呼叫端預設並沒有記錄。若相關系統或廠商不配合主動提供，要追查Web Service/WCF的呼叫是否出錯就變得格外困難。

要解決這樣的難題，最簡單的做法就是每次呼叫WCF/WS時，將傳入參數以及對方的回應寫入Log檔。不過，找出所有呼叫WCF/WS的程式片段，再依不同方法不同參數硬刻(Hard-Coding)出寫Log的程式碼顯然有點愚公移山。於是我有個點子，何不針對該WCF/WS建立一個LogWrapper類別，提供與各WebMethod完全相同參數與傳回型別的介面。當呼叫端呼叫時，LogWrapper先偷偷將所有傳入參數寫入Log檔，再呼叫遠端真正的WCF/WS；取得結果後，先將結果寫入Log檔，再把結果傳回呼叫端。如此，呼叫端只要將原本直接呼叫WCF/WS的程式稍做修改，改呼叫LogWrapper，我們就能保留呼叫歷程的詳細記錄，要追查問題就方便多了!

我用一個很簡單(且無聊)的WCF來示範:

public class SpiderManService : ISpiderManService

    public string SuperCalc(int x, int y)

        return string.Format("{0} + {1} = {2}",

            x, y, x + y);

在ASP.NET專案中Add Service Reference後，我們可使用SpiderManServiceClient Class來呼叫它:

    protected void Page_Load(object sender, EventArgs e)

        SMS.SpiderManServiceClient smsc = new SMS.SpiderManServiceClient();

        Response.Write(smsc.SuperCalc(1, 1));

        Response.End();

下一步，我們就來產生一個SpideManServiceClientLogWrapper，把SuperCalc方法包起來! 借助.NET神奇的Reflection功能，我寫了一個LogWrapper程式碼產生器:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Reflection;

using System.Text;

public class LogWrapperCodeGen

    public static string GenWrapperClass(Type t)

        StringBuilder sb = new StringBuilder();

        sb.AppendLine(@"using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Xml;

using System.Text;

using System.IO;

");

        sb.AppendFormat("public class {0}LogWrapper", t.ToString().Split('.').Last());

        sb.AppendLine(@"

    class Logger

        public string MethodName;

        public string LogPath;

        private StringBuilder sb = new StringBuilder();

        private void log(string msg)

            sb.AppendFormat(""{0:yyyy/MM/dd HH:mm:ss.fff} {1}\r\n"", DateTime.Now, msg);

        private void log(string fmt, params object[] args)

            log(string.Format(fmt, args));

        public Logger(string methodName)

            MethodName = methodName;

            LogPath = HttpContext.Current.Server.MapPath(

                string.Format(""~/App_Data/WSLog/{0:yyyyMMdd}.txt"", DateTime.Today));

            log(new String('=', 80));

            log(""Url = "" + HttpContext.Current.Request.Url.ToString());

            log(""IP = "" + HttpContext.Current.Request.UserHostAddress);

            log(""Call Method[{0}]"", methodName);

        public void LogParam(string paramName, object paramValue)

            log(""  Parameter[{0}] => {1}"", paramName, paramValue);

        public void LogResult(string result)

            log(""  Result => {0}"", result);

        public void Flush()

            using (StreamWriter sw = new StreamWriter(LogPath, true))

                sw.Write(sb.ToString());

");

        foreach (MethodInfo mi in t.GetMethods(

            //BindingFlags.DeclaredOnly 可以排除繼承來的Method

            BindingFlags.Instance | BindingFlags.Public | BindingFlags.DeclaredOnly))

            sb.AppendFormat("    public static {1} {0} (", mi.Name, mi.ReturnType.ToString());

            sb.Append(

                string.Join(", ", mi.GetParameters()

                .Select(o => string.Format("{0} {1}", o.ParameterType.ToString(), o.Name))

                .ToArray()));

            sb.AppendLine(")");

            sb.AppendLine("    {");

            sb.AppendFormat("        Logger log = new Logger(\"{0}\");\r\n", mi.Name);

            foreach (ParameterInfo pi in mi.GetParameters())

                sb.AppendFormat("        log.LogParam(\"{0}\", {0});\r\n", pi.Name);

            sb.AppendFormat("        {0} objWS = new {0}();\r\n", t.ToString());

            sb.AppendFormat("        {1} result = objWS.{0}(",

                mi.Name, mi.ReturnType.ToString());

            sb.Append(

                string.Join(", ",

                mi.GetParameters().Select(o => string.Format("{0}", o.Name)).ToArray()));

            sb.AppendLine(");");

            sb.AppendLine("        log.LogResult(result.ToString());");

            sb.AppendLine("        log.Flush();");

            sb.AppendLine("        return result;");

            sb.AppendLine("    }");

        sb.AppendLine("}");

        return sb.ToString();

呼叫LogWrapperCodeGen.GenWrapperClass(typeof(SMS.SpiderManServiceClient))，就可以得到SpiderManServiceClientLogWrapper的程式碼如下:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Xml;

using System.Text;

using System.IO;

public class SpiderManServiceClientLogWrapper

    class Logger

        public string MethodName;

        public string LogPath;

        private StringBuilder sb = new StringBuilder();

        private void log(string msg)

            sb.AppendFormat("{0:yyyy/MM/dd HH:mm:ss.fff} {1}\r\n", DateTime.Now, msg);

        private void log(string fmt, params object[] args)

            log(string.Format(fmt, args));

        public Logger(string methodName)

            MethodName = methodName;

            LogPath = HttpContext.Current.Server.MapPath(

                string.Format("~/App_Data/WSLog/{0:yyyyMMdd}.txt", DateTime.Today));

            log(new String('=', 80));

            log("Url = " + HttpContext.Current.Request.Url.ToString());

            log("IP = " + HttpContext.Current.Request.UserHostAddress);

            log("Call Method[{0}]", methodName);

        public void LogParam(string paramName, object paramValue)

            log("  Parameter[{0}] => {1}", paramName, paramValue);

        public void LogResult(string result)

            log("  Result => {0}", result);

        public void Flush()

            using (StreamWriter sw = new StreamWriter(LogPath, true))

                sw.Write(sb.ToString());

    public static System.String SuperCalc (System.Int32 x, System.Int32 y)

        Logger log = new Logger("SuperCalc");

        log.LogParam("x", x);

        log.LogParam("y", y);

        SMS.SpiderManServiceClient objWS = new SMS.SpiderManServiceClient();

        System.String result = objWS.SuperCalc(x, y);

        log.LogResult(result.ToString());

        log.Flush();

        return result;

將以上Class放進App_Code，再修改呼叫程式，改成SpiderManServiceClientLogWrapper.SuperCalc(1, 1):

    protected void Page_Load(object sender, EventArgs e)

        //SMS.SpiderManServiceClient smsc = new SMS.SpiderManServiceClient();

        //Response.Write(smsc.SuperCalc(1, 1));

        Response.Write(SpiderManServiceClientLogWrapper.SuperCalc(1, 1));

        Response.End();

就可以在App_Data/WSLog/yyyyMMdd.txt中找到詳細的呼叫記錄囉!

2010/10/21 05:38:16.852 ================================================================================
2010/10/21 05:38:16.852 Url = httq://localhost/ASPNET35/Default.aspx
2010/10/21 05:38:16.852 IP = ::1
2010/10/21 05:38:16.853 Call Method[SuperCalc]
2010/10/21 05:38:16.853   Parameter[x] => 1
2010/10/21 05:38:16.853   Parameter[y] => 1
2010/10/21 05:38:16.875   Result => 1 + 1 = 2

有了詳細呼叫Log，不管是要偵錯抓蟲射茶包，還是準備起訴抗辯上公堂，都能無往不利! (提到這點，相信老鳥們應該會發出會心一笑吧~)

Comments

# 2010-10-21 12:45 AM by Lan

我遇過某鳥廠幹的好事是這樣 : 寫進Log的是A,傳出去的變成A'

# 2010-10-21 05:57 AM by chicken

這種苦差事可以用 Policy Injection 方式，解的比較漂亮 :D 尤其像 WCF 這種已經是 remoting 型態的機制了，應該有更簡單的地方可以插入 Logging code.. http://columns.chicken-house.net/post/2008/11/18/Policy-Injection-Application-Block-e5b08fe799bce78fbe.aspx

Comments

# 2010-10-21 12:45 AM by Lan

# 2010-10-21 05:57 AM by chicken

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