背景：實(shí)現(xiàn)blog網(wǎng)站，每篇文章的點(diǎn)播數(shù)統(tǒng)計(jì)。

簡單實(shí)現(xiàn)方法：文章每次被打開時update一下數(shù)據(jù)庫。如：

Update blog set visitcount=visitcount+1 where blogid=’文章ID’.

當(dāng)然了，對于一些小型網(wǎng)站，根本沒有什么人訪問，這種實(shí)現(xiàn)方案完全沒有問題。但是對于訪問量比較大的網(wǎng)站，這種實(shí)現(xiàn)方案，很容易造成數(shù)據(jù)庫over掉。

而且在執(zhí)行update的時候，大多數(shù)據(jù)庫默認(rèn)都是使用排它鎖的，這條數(shù)據(jù)是被鎖住的，別人無法使用。訪問量大，被鎖住的機(jī)率也就大了。

我的方案：

先把統(tǒng)計(jì)數(shù)據(jù)緩存起來，每N秒鐘寫一次數(shù)據(jù)庫，這樣就大大的減少了數(shù)據(jù)庫的連接次數(shù)，以及數(shù)據(jù)被鎖住的機(jī)率。

緩存實(shí)現(xiàn)方案：

定義兩個hashtable（t1,t2）。一個讀一個寫（讀：從client接收數(shù)據(jù)。寫：數(shù)據(jù)寫入數(shù)據(jù)庫）。每隔N秒寫一次數(shù)據(jù)庫。寫數(shù)據(jù)庫的時候最好采用異步的方式進(jìn)行，以防止線程長期占用hashtable(讀).

DEMO：

統(tǒng)計(jì)代碼：VisitStatistic.ashx

在Blog文章頁面中加入標(biāo)簽<script src=” VisitStatistic.ashx”></script>

VisitStatistic.ashx

代碼：

    public class VisitStatistic : IHttpHandler

    {

        public void ProcessRequest(HttpContext context)

        {

            context.Response.ContentType = "text/plain";

            Statistic();

            context.Response.Write("");

        }

        private static object threadLock = new object();

        private static Hashtable t1 = Hashtable.Synchronized(new Hashtable());

        private static Hashtable t2 = Hashtable.Synchronized(new Hashtable());

        private static Timer time = new Timer(WriteToDb, null, 10, 6000);

        private static string readtb = "t1";

        private static bool isworking = false;

        private void Statistic()

        {

            lock (threadLock)

            {

                Hashtable ht = WriteTb;

                if (ht.ContainsKey(BlogId))

                {

                    ht[BlogId] = (int)ht[BlogId] + 1;

                }

                else

                {

                    ht.Add(BlogId, 1);

                }

            }

        }

        private static void WriteToDb(object obj)

        {

            if(isworking) return;

            isworking = true;

            Hashtable tb = ReadTb;

            IDictionaryEnumerator enumerator = tb.GetEnumerator();

            List<BlogStatistic> items = new List<BlogStatistic >(tb.Count);

            while (enumerator.MoveNext())

            {

                BlogStatistic item = new BlogStatistic () {

                    VisitCount = (int)enumerator.Value,

                    BlogId = (int)enumerator.Key

                };

                items.Add(item);

            }

            tb.Clear();

            if (items.Count > 0)

            {

                ThreadPool.QueueUserWorkItem(AsynWriteToDb, items);

            }

         

            if (readtb == "t1") readtb = "t2";

            else readtb = "t1";

            isworking = false;

        }

        private static void AsynWriteToDb(object items)

        {

           

            try

            {

               

                BlogBusiness business = new BlogBusiness ();

                business.AddBlogStatistic((List<BlogStatistic>)items);

            }

            catch (Exception ex)

            {

                LogMessage msg = new LogMessage(){

                    Message = "統(tǒng)計(jì)數(shù)寫入數(shù)據(jù)庫異常"

                };

                LogHelper.Error(msg, ex);

            }

        }

        private int BlogId

        {

            get

            {

                string util = HttpContext.Current.Request["blogid"];

                if(string.IsNullOrEmpty(util)

                    ||!Regex.IsMatch(util,@"^"d+$"))

                {

                    HttpContext.Current.Response.End();

                }

                return int.Parse(util);

            }

        }

        private static Hashtable ReadTb

        {

            get

            {

                if (readtb == "t1")

                {

                    return t1;

                }

                else

                {

                    return t2;

                }

            }

        }

        private static Hashtable WriteTb

        {

            get

            {

                if (readtb == "t1")

                {

                    return t2;

                }

                else

                {

                    return t1;

                }

            }

        }

        public bool IsReusable

        {

            get

            {

                return false;

            }

        }

    }