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本讲是通过DbCommand拦截器来实现读写分离的最后一讲，对之前几篇文章做了一个优化，无论是程序可读性还是实用性上都有一个提升，在配置信息这块，去除了字符串方式的拼接，取而代之的是section数组，这样在修改配置时更加清晰了；而实用性上，彻底改变了读和写不能共用一个仓储对象的缺点，并且在一个事务里可以读写并存，并为了数据的一致性，使事务里的curd操作指向主库，这一点很重要！
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 (2015-01-09 17:52)
EF架构~通过EF6的DbCommand拦截器来实现数据库读写分离~续~添加事务机制 (2015-01-08 14:08)
EF架构~通过EF6的DbCommand拦截器来实现数据库读写分离 (2015-01-07 17:31)
一 配置文件的修改
<configSections>
<section name="DistributedReadWriteSection" type="Project.DistributedReadWriteForEF.DistributedReadWriteSectionHandler, Project.DistributedReadWriteForEF"/>
</configSections>
<DistributedReadWriteSection>
<add key="readDb1" Ip="192.168.2.71" Port="1433" DbName="background_read1" UserId="sa" Password="zzl123" />
<add key="readDb2" Ip="192.168.2.71" Port="1433" DbName="TestWrite_Read_Zzl" UserId="sa" Password="zzl123" />
<add key="readDb3" Ip="192.168.2.29" Port="1433" DbName="TestWrite_Read_Zzl" UserId="sa" Password="1" />
</DistributedReadWriteSection>
<appSettings>
<!-- 只读服务器的sql连接串配置模版-->
<add key ="readDbConnection" value="data source={0};initial catalog={1};persist security info=True;user id={2};password={3};multipleactiveresultsets=True;application name=EntityFramework"/>
<add key ="writeDbConnection" value="data source=.;initial catalog=background;persist security info=True;user id=sa;password=zzl123;multipleactiveresultsets=True;application name=EntityFramework"/>
</appSettings>
/// <summary> /// redis配置信息加载 /// </summary> internal class DistributedReadWriteManager { /// <summary> /// 配置信息实体 /// </summary> public static IList<DistributedReadWriteSection> Instance { get { return GetSection(); } } private static IList<DistributedReadWriteSection> GetSection() { var dic = ConfigurationManager.GetSection("DistributedReadWriteSection") as Dictionary<string, DistributedReadWriteSection>; return dic.Values.ToList(); } }
/// <summary> /// DistributedReadWriteForEFSection块，在web.config中提供DistributedReadWriteForEFSection块定义 /// </summary> internal class DistributedReadWriteSection : ConfigurationSection { /// <summary> /// 主机地址 /// </summary> [ConfigurationProperty("Ip", DefaultValue = "127.0.0.1")] public string Ip { get { return (string)this["Ip"]; } set { this["Ip"] = value; } } /// <summary> /// 端口号 /// </summary> [ConfigurationProperty("Port", DefaultValue = "1433")] public int Port { get { return (int)this["Port"]; } set { this["Port"] = value; } } /// <summary> /// 数据库名称 /// </summary> [ConfigurationProperty("DbName", DefaultValue = "Test")] public string DbName { get { return (string)this["DbName"]; } set { this["DbName"] = value; } } /// <summary> /// 数据库账号 /// </summary> [ConfigurationProperty("UserId", DefaultValue = "sa")] public string UserId { get { return (string)this["UserId"]; } set { this["UserId"] = value; } } /// <summary> /// 数据库账号 /// </summary> [ConfigurationProperty("Password", DefaultValue = "sa")] public string Password { get { return (string)this["Password"]; } set { this["Password"] = value; } } }
internal class DistributedReadWriteSectionHandler : IConfigurationSectionHandler { #region IConfigurationSectionHandler 成员 public object Create(object parent, object configContext, System.Xml.XmlNode section) { Dictionary<string, DistributedReadWriteSection> names = new Dictionary<string, DistributedReadWriteSection>(); string _key = string.Empty; string _ip = string.Empty; string _dbName = string.Empty; string _userId = string.Empty; string _password = string.Empty; int _port = 1433; foreach (XmlNode childNode in section.ChildNodes) { if (childNode.Attributes["key"] != null) { _key = childNode.Attributes["key"].Value; if (childNode.Attributes["Ip"] != null) { _ip = childNode.Attributes["Ip"].Value; } if (childNode.Attributes["Port"] != null) { _port = Convert.ToInt32(childNode.Attributes["Port"].Value); } if (childNode.Attributes["DbName"] != null) { _dbName = childNode.Attributes["DbName"].Value; } if (childNode.Attributes["UserId"] != null) { _userId = childNode.Attributes["UserId"].Value; } if (childNode.Attributes["Password"] != null) { _password = childNode.Attributes["Password"].Value; } names.Add(_key, new DistributedReadWriteSection { Ip = _ip, Port = _port, DbName = _dbName, UserId = _userId, Password = _password }); } } return names; } #endregion }
二 仓储大叔事务块修改
public static void UsingNoMsdtc(IUnitOfWork db, bool isOutest, Action action) { var objectContext = ((System.Data.Entity.Infrastructure.IObjectContextAdapter)db).ObjectContext; try { objectContext.Connection.Close(); //强制将所有curd操作维持到主库 Project.DistributedReadWriteForEF.CommandInterceptor.IsTransactionScope = true; //重新设置链接串 if (System.Configuration.ConfigurationManager.AppSettings["writeDbConnection"] != null) objectContext.TransactionHandler.DbContext.Database.Connection.ConnectionString = System.Configuration.ConfigurationManager.AppSettings["writeDbConnection"]; objectContext.Connection.Open(); using (TransactionScope trans = new TransactionScope()) { action(); trans.Complete(); Project.DistributedReadWriteForEF.CommandInterceptor.IsTransactionScope = false;//事务结束将走读写分离 } } finally { if (isOutest)//如果是最外层事务，再将连接关闭！内部事务与外部事务需要共用一个Connection的连接 objectContext.Connection.Close(); //只能关闭,不能dispose,因为dispose之后,上下文就无法得到链接串了 } }
三 DbCommand拦截器的修改
/// <summary> /// SQL命令拦截器 /// 主要实现EF的读写分离 /// </summary> public class CommandInterceptor : DbCommandInterceptor { static CommandInterceptor() { readConnList = DistributedReadWriteManager.Instance; sysTimer.Enabled = true; sysTimer.Elapsed += sysTimer_Elapsed; sysTimer.Start(); } /// <summary> /// 是否在一个事务中，如果是select,insert,update,delete都走主库 /// ThreadStatic标识它只在当前线程有效 /// </summary> [ThreadStatic] public static bool IsTransactionScope = false; /// <summary> /// 锁住它 /// </summary> 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(5000); /// <summary> /// 读库，从库集群，写库不用设置走默认的EF框架 /// </summary> private static IList<DistributedReadWriteSection> readConnList; #region Private Methods private static void sysTimer_Elapsed(object sender, ElapsedEventArgs e) { 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["readDbConnection"] , resultConn.Ip , resultConn.DbName , resultConn.UserId , resultConn.Password); } return string.Empty; } /// <summary> /// 只读库的选择,加工command对象 /// 说明：事务中,所有语句都走主库，事务外select走读库,insert,update,delete走主库 /// 希望：一个ＷＥＢ请求中，读与写的仓储使用一个，不需要在程序中去重新定义 /// </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 { command.Connection.Close(); if (!command.CommandText.StartsWith("insert", StringComparison.InvariantCultureIgnoreCase) && !IsTransactionScope) 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 }
好了，到这里，通过拦截器来实现数据库读写分离的方案就彻底完成了，这个版本应该算是个终级了吧，呵呵！感谢您的阅读！
EF架构~通过EF6的DbCommand拦截器来实现数据库读写分离~终结~配置的优化和事务里读写的统一
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原文地址：http://www.cnblogs.com/lori/p/4218349.html
