EF架构~通过EF6的DbCommand拦截器来实现数据库读写分离~再续~添加对各只读服务器的心跳检测

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上一讲中基本实现了对数据库的读写分离，而在选择只读数据库上只是随机选择，并没有去检测数据库服务器是否有效，如服务器挂了，ＳＱＬ服务停了，端口被封了等等，而本讲主要对以上功能进行一个实现，并对配置文件也进行了一些优化，让它更好的支持多个数据库服务器，分别配置各个的账号和密码及数据库服务端口等等，接下来，就来看一下主要的代码吧。

一　配置文件

    <!-- ef实现对sql读写分离的配置，sqlserver端采用发布与订阅实现 -->
    <add key="readDb" value="
         192.168.2.71|1433|background_read1|sa|zzl123,
         192.168.2.71|1433|TestWrite_Read_Zzl|sa|zzl123,
         192.168.2.29|1433|TestWrite_Read_Zzl|sa|1"
         />
    <!-- 只读服务器的sql连接串配置模版-->
    <add key ="readDbConnectioin" value="data source={0};initial catalog={1};persist security info=True;user id={2};password={3};multipleactiveresultsets=True;application name=EntityFramework"/>

二　数据库配置实体类

 /// <summary>
    /// 只读数据库配置实体
    /// </summary>
    public class ReadDbConfig
    {
        public ReadDbConfig()
        {
            Port = 1433;
            UserId = "sa";
        }
        public string Ip { get; set; }
        public int Port { get; set; }
        public string DbName { get; set; }
        public string UserId { get; set; }
        public string Password { get; set; }
    }

三　对ＳＱＬ拦截器进行优化，添加了TCP的心跳检测

lock (lockObj)
            {
                if (readConnList != null && readConnList.Any())
                {
                    foreach (var item in readConnList)
                    {
                        //心跳测试，将死掉的服务器IP从列表中移除
                        var client = new TcpClient();
                        try
                        {
                            client.Connect(new IPEndPoint(IPAddress.Parse(item.Ip), item.Port));
                        }
                        catch (SocketException)
                        {
                            //异常，没有连接上
                            readConnList.Remove(item);
                        }
                        if (!client.Connected)
                        {
                            readConnList.Remove(item);
                        }
                    }
                }
            }

四　对于数据库库端还是这前通过发布和订阅实现的，需要注意的是，这些功能需要使用“机器名”进行链接，使用ip和域名都是无效的

五　下面贡献一下完成的拦截器代码

    /// <summary>
    /// SQL命令拦截器
    /// 主要实现EF的读写分离
    /// </summary>
    public class SqlCommandInterceptor : DbCommandInterceptor
    {
        static SqlCommandInterceptor()
        {
            InitConfig();

            initSysTimer.Enabled = true;
            initSysTimer.Elapsed += initSysTimer_Elapsed;
            initSysTimer.Start();

            sysTimer.Enabled = true;
            sysTimer.Elapsed += sysTimer_Elapsed;
            sysTimer.Start();
        }

        private static object lockObj = new object();
        /// <summary>
        /// 定期找没有在线的数据库服务器
        /// </summary>
        private static Timer sysTimer = new Timer(6);
        /// <summary>
        /// 系统配置文件轮训读时间间隔
        /// </summary>
        private static Timer initSysTimer = new Timer(60000 * 10);
        /// <summary>
        ///　读库，从库集群，写库不用设置走默认的EF框架
        /// </summary>
        private static List<ReadDbConfig> readConnList;
        /// <summary>
        /// 配置初始化
        /// </summary>
        private static void InitConfig()
        {
            lock (lockObj)
            {
                var temp = new List<ReadDbConfig>();
                var str = System.Configuration.ConfigurationManager.AppSettings["readDb"] ?? string.Empty;
                var readList = str.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
                if (readList != null && readList.Any())
                {
                    foreach (var item in readList)
                    {
                        var configArr = item.Split(new char[] { '|' }, StringSplitOptions.RemoveEmptyEntries);
                        temp.Add(new ReadDbConfig
                        {
                            Ip = configArr[0],
                            Port = int.Parse(configArr[1]),
                            DbName = configArr[2],
                            UserId = configArr[3],
                            Password = configArr[4],
                        });
                    }
                }
                readConnList = temp;
            }
        }
        #region Private Methods
        private static void initSysTimer_Elapsed(object sender, ElapsedEventArgs e)
        {
            InitConfig();
        }
        /// <summary>
        /// 轮询服务
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private static void sysTimer_Elapsed(object sender, ElapsedEventArgs e)
        {
            lock (lockObj)
            {
                if (readConnList != null && readConnList.Any())
                {
                    foreach (var item in readConnList)
                    {
                        //心跳测试，将死掉的服务器IP从列表中移除
                        var client = new TcpClient();
                        try
                        {
                            client.Connect(new IPEndPoint(IPAddress.Parse(item.Ip), item.Port));
                        }
                        catch (SocketException)
                        {
                            //异常，没有连接上
                            readConnList.Remove(item);
                        }
                        if (!client.Connected)
                        {
                            readConnList.Remove(item);
                        }
                    }
                }
            }
        }
        /// <summary>
        /// 处理读库字符串
        /// </summary>
        /// <returns></returns>
        private string GetReadConn()
        {
            if (readConnList != null && readConnList.Any())
            {
                var resultConn = readConnList[Convert.ToInt32(Math.Floor((double)new Random().Next(0, readConnList.Count)))];
                return string.Format(System.Configuration.ConfigurationManager.AppSettings["readDbConnectioin"]
                    , resultConn.Ip
                    , resultConn.DbName
                    , resultConn.UserId
                    , resultConn.Password);
            }
            return string.Empty;
        }
        /// <summary>
        /// 只读库的选择,加工command对象
        /// </summary>
        /// <param name="command"></param>
        private void ReadDbSelect(DbCommand command)
        {
            if (!string.IsNullOrWhiteSpace(GetReadConn()))//如果配置了读写分离，就去实现
            {
                if (!command.CommandText.StartsWith("insert", StringComparison.InvariantCultureIgnoreCase))
                {
                    command.Connection.Close();
                    command.Connection.ConnectionString = GetReadConn();
                    command.Connection.Open();
                }
            }
        }
        #endregion

        #region Override Methods
        /// <summary>
        /// Linq to Entity生成的update,delete
        /// </summary>
        /// <param name="command"></param>
        /// <param name="interceptionContext"></param>
        public override void NonQueryExecuting(DbCommand command, DbCommandInterceptionContext<int> interceptionContext)
        {
            base.NonQueryExecuting(command, interceptionContext);//update,delete等写操作直接走主库
        }
        /// <summary>
        /// 执行sql语句，并返回第一行第一列，没有找到返回null,如果数据库中值为null，则返回 DBNull.Value
        /// </summary>
        /// <param name="command"></param>
        /// <param name="interceptionContext"></param>
        public override void ScalarExecuting(DbCommand command, DbCommandInterceptionContext<object> interceptionContext)
        {
            ReadDbSelect(command);
            base.ScalarExecuting(command, interceptionContext);
        }
        /// <summary>
        /// Linq to Entity生成的select,insert
        /// 发送到sqlserver之前触发
        /// warning:在select语句中DbCommand.Transaction为null，而ef会为每个insert添加一个DbCommand.Transaction进行包裹
        /// </summary>
        /// <param name="command"></param>
        /// <param name="interceptionContext"></param>
        public override void ReaderExecuting(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
        {
            ReadDbSelect(command);
            base.ReaderExecuted(command, interceptionContext);
        }
        /// <summary>
        /// 发送到sqlserver之后触发
        /// </summary>
        /// <param name="command"></param>
        /// <param name="interceptionContext"></param>
        public override void ReaderExecuted(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
        {
            base.ReaderExecuted(command, interceptionContext);
        }

        #endregion
    }

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