1. 开始
对于分布式的缓存，平常的session的处理是一个用户对应一台分布式的机器，如果这台机器中途挂机或者不能处理这个用户session的情况发生，则此用户的session会丢失，会发生不可预知的错误。如下图：
如果用Redis的分布式缓存，则能避免上面的情况。因为session是保存在Redis中，不会有丢失的情况，就算中途有服务器A挂掉。如下图：
2. 代码
1）在包管理器中，输入下面的包，安装
Install-Package Microsoft.Web.RedisSessionStateProvider
2）可以看到web.config中自动添加了以下代码：
<sessionState mode="Custom" customProvider="MySessionStateStore" timeout="">
<providers>
<!-- For more details check https://github.com/Azure/aspnet-redis-providers/wiki -->
<!-- Either use 'connectionString' OR 'settingsClassName' and 'settingsMethodName' OR use 'host','port','accessKey','ssl','connectionTimeoutInMilliseconds' and 'operationTimeoutInMilliseconds'. -->
<!-- 'throwOnError','retryTimeoutInMilliseconds','databaseId' and 'applicationName' can be used with both options. -->
<!--
<add name="MySessionStateStore"
host = "127.0.0.1" [String]
port = "" [number]
accessKey = "" [String]
ssl = "false" [true|false]
throwOnError = "true" [true|false]
retryTimeoutInMilliseconds = "" [number]
databaseId = "" [number]
applicationName = "" [String]
connectionTimeoutInMilliseconds = "" [number]
operationTimeoutInMilliseconds = "" [number]
connectionString = "<Valid StackExchange.Redis connection string>" [String]
settingsClassName = "<Assembly qualified class name that contains settings method specified below. Which basically return 'connectionString' value>" [String]
settingsMethodName = "<Settings method should be defined in settingsClass. It should be public, static, does not take any parameters and should have a return type of 'String', which is basically 'connectionString' value.>" [String]
loggingClassName = "<Assembly qualified class name that contains logging method specified below>" [String]
loggingMethodName = "<Logging method should be defined in loggingClass. It should be public, static, does not take any parameters and should have a return type of System.IO.TextWriter.>" [String]
redisSerializerType = "<Assembly qualified class name that implements Microsoft.Web.Redis.ISerializer>" [String]
/>
-->
<add name="MySessionStateStore"
type="Microsoft.Web.Redis.RedisSessionStateProvider"
host="ceswebchat.redis.cache.chinacloudapi.cn"
accessKey="m1JuDEstaqA+xxxxxxxxxxx"
ssl="false"
throwOnError = "true"
retryTimeoutInMilliseconds = ""
connectionTimeoutInMilliseconds = ""
operationTimeoutInMilliseconds = ""
databaseId = ""
/>
</providers>
</sessionState>
上面可以看到，输入你所需的信息就可以了。很简单
- host – Redis Cache的host name/endpoint
- port – 使用你的Redis Cache的SSL port或者非SSL port，这取决你的ssl设置的值
- accessKey – Redis Cache的Keys
- ssl – true (Cache/Client之间安全的通信); 否则设为 false
- 默认禁用 non-SSL port，有关启用 non-SSL port，参阅 Access Ports
- throwOnError – true (在事件出错时抛出异常)，否则设为 false. 你可以在静态属性 Microsoft.Web.Redis.RedisSessionStateProvider.LastException检查异常信息， 默认为true。
- retryTimeoutInMilliseconds – 在此时间间隔内重试操作(单位：毫秒)
- databaseId – 指定一个数据库用来存储缓存输入数据。如果未指定，默认值为0。
- applicationName – 缓存key存储在Redis中命名规则为：
{<Application Name>_<Session ID>}_Data，如果多个应用程序共享相同的key，则这个参数是可选的。 如果不设置该参数将使用默认值。 - connectionTimeoutInMilliseconds – 这个设置会覆盖connectTimeout参数设置。如果未设置，那么会使用默认的connectTimeout值5000，详情请参考 StackExchange.Redis configuration model.
- operationTimeoutInMilliseconds – 这个设置会覆盖syncTimeout参数设置。如果未设置，那么会使用默认的syncTimeout值1000，详情请参考 StackExchange.Redis configuration model.