DMSFrame 之SqlCacheDependency（二）

上篇文章介绍的是通知模式的缓存机制,这里介绍的是数据库轮循模式处理,这种模式对SQL2005以下的支持还是比较好的

引擎源码如下:

/// <summary>
    /// 轮循模式
    /// 数据库缓存通知模式
    /// 1.SELECT  DATABASEPROPERTYEX('DATABASENAME','IsBrokerEnabled') 1 表示启用，0表示未启用
    /// 2.启用IsBrokerEnabled
    /// ALTER DATABASE [DATABASENAME] SET NEW_BROKER WITH ROLLBACK IMMEDIATE;
    /// ALTER DATABASE [DATABASENAME] SET ENABLE_BROKER;/ALTER DATABASE [DATABASENAME] SET DISABLE_BROKER;
    /// 3.web.config 添加配置信息
    /// connectionStrings
    /// 4.设置aspnet_regsql.exe的信息,aspnet_regsql –S 服务器名 –U 登陆名 ID –P 密码 –d 数据库名  –ed
    /// </summary>
    [Obsolete("适用于数据库2005以下，2005以上请使用DMSLinqSqlWebCacheNotifyProvider")]
    public class DMSLinqSqlWebCacheProvider : IDMSLinqCacheProvider
    {

        System.Web.Caching.Cache webCache = System.Web.HttpRuntime.Cache;
        private static object syncObj = new object();
        public DMSLinqSqlWebCacheProvider()
        {
            lock (syncObj)
            {
                System.Web.HttpContext context = System.Web.HttpContext.Current;
                if (context != null)
                    webCache = context.Cache;
                else
                    webCache = System.Web.HttpRuntime.Cache;
            }
        }

        public string GetDependencyKey(System.Data.IDbCommand command, string[] tableNames)
        {
            string dependencyKey = command.CommandText;
            foreach (System.Data.IDbDataParameter item in command.Parameters)
            {
                dependencyKey += string.Format("-{0}-{1}", item.ParameterName, item.Value);
            }
#if DEBUG
            System.Diagnostics.Debug.WriteLine(string.Format("{0},use dependency key successfully", dependencyKey));
#endif
            return dependencyKey;
        }

        public object GetCache(string dependencyKey)
        {
            object resultValue = webCache[dependencyKey];
#if DEBUG
            System.Diagnostics.Debug.WriteLine(string.Format("this cache is empty?：{0}", resultValue == null ? "true" : "false"));
#endif
            return resultValue;
        }
        public System.Web.Caching.CacheDependency GetCacheDependency(string connectionString, System.Data.IDbCommand command, string[] tableNames, ref string dependencyKey)
        {
            CacheDependency dependency = null;
            try
            {
                SqlCacheDependencyAdmin.EnableNotifications(connectionString);
                if (!SqlCacheDependencyAdmin.GetTablesEnabledForNotifications(connectionString).Contains(tableNames[0]))
                {
                    SqlCacheDependencyAdmin.EnableTableForNotifications(connectionString, tableNames[0]);
                }
                if (tableNames.Length == 1)
                {
                    dependency = new SqlCacheDependency("DefaultValue", tableNames[0]);
                }
                else
                {
                    AggregateCacheDependency dependency0 = new AggregateCacheDependency();
                    foreach (var item in tableNames)
                    {
                        dependency0.Add(new SqlCacheDependency("DefaultValue", item));
                    }
                    dependency = dependency0;
                }

            }
            catch (Exception ex)
            {
                DMSFrame.Loggers.LoggerManager.Logger.Log(ex, ReflectionUtils.GetMethodBaseInfo(System.Reflection.MethodBase.GetCurrentMethod()), DMSFrame.Loggers.ErrorLevel.Fatal);
            }
#if DEBUG
            System.Diagnostics.Debug.WriteLine(string.Format("Get the sqlcachedependency successfully.{0}", dependency == null ? "false" : "true"));
#endif
            return dependency;
        }
        public void SetCache(System.Web.Caching.CacheDependency dependency, string dependencyKey, object Value)
        {
            if (dependency != null)
            {
#if DEBUG
                System.Diagnostics.Debug.WriteLine(string.Format("Add cache is successfully,{0}", dependencyKey));
#endif
                webCache.Insert(dependencyKey, Value, dependency);
            }
        }
    }

同样的,代码也要配置一下.

<configSections>
    <section name="DMSLinqCacheProvider" type="DMSFrame.Cache.DMSLinqCacheProvider,DMSFrame"/>
  </configSections>
  <DMSLinqCacheProvider>
    <add key="provider" providerName="MsSql" value="DMSFrame.Cache.DMSLinqSqlWebCacheProvider,DMSFrame"/>
  </DMSLinqCacheProvider>

注意,此处理配置的数据库连接name必须是 DefaultValue,至于为什么是这个,可以看下引擎源码..呵呵,这里就不解释了.....

<connectionStrings>
    <add  name="DefaultValue" providerName="System.Data.SqlClient" connectionString="Integrated Security=False;server=127.0.0.1;database=DATABASE;User ID=sa;Password=sa;Connect Timeout=30;"/>
  </connectionStrings>

 增加支持 sqlCacheDependency 的配置,轮循时间为1000毫秒

 <system.web>    
    <caching>
      <sqlCacheDependency enabled="true" pollTime="1000">
        <databases>
          <add name="DefaultValue" connectionStringName="DefaultValue" pollTime="500" />
        </databases>
      </sqlCacheDependency>
    </caching>
  </system.web>

注: databases也可以重写轮循时间的哦...呼呼,不要以为这样就可以了哦..

还要再检查我们数据库是否支持这个模式的方式呢.这种模式查询SQL会自动在表 AspNet_SqlCacheTablesForChangeNotification 添加一行数据..每更新,删除,插入一次都会增加(更新)一数据的.

怎么开启AspNet_SqlCacheTablesForChangeNotification 这个..具体可以参考 

1.为 SQL Server 启用缓存通知
aspnet_regsql.exe -S <Server> -U <Username> -P <Password> -ed -d Northwind -et -t Employees
为 Northwind 数据库中的 Employees 表启用缓存通知
aspnet_regsqlcache –S 服务器名称 –U 登陆ID –P 密码 –d 数据库名称 –t 要追踪的数据表的名称 –et

注:这种模式比较耗数据库性能哦!!!!强烈建议用通知模式吧,具体参考文章:

DMSFrame 之SqlCacheDependency（一）