ASP.NET Session State Provider for Azure Cache for Redis

Azure Cache for Redis provides a session state provider that you can use to store your session state in-memory with Azure Cache for Redis instead of a SQL Server database. To use the caching session state provider, first configure your cache, and then configure your ASP.NET application for cache using the Azure Cache for Redis Session State NuGet package. For ASP.NET Core applications, read Session and state management in ASP.NET Core.

It's often not practical in a cloud app to avoid storing some form of state for a user session, but some approaches affect performance and scalability more than others. If you have to store state, the best solution is to keep the amount of state small and store it in cookies. If that isn't feasible, the next best solution is to use ASP.NET session state with a provider for distributed, in-memory cache. The worst solution from a performance and scalability standpoint is to use a database-backed session state provider. This article provides guidance on using the ASP.NET Session State Provider for Azure Cache for Redis. For information on other session state options, see ASP.NET Session State options.

Store ASP.NET session state in the cache

To configure a client application in Visual Studio using the Azure Cache for Redis Session State NuGet package, select NuGet Package Manager, Package Manager Console from the Tools menu.

Run the following command from the Package Manager Console window.

Install-Package Microsoft.Web.RedisSessionStateProvider

The Redis Session State Provider NuGet package has a dependency on the StackExchange.Redis package. If the StackExchange.Redis package isn't present in your project, it's installed.

The NuGet package downloads and adds the required assembly references and adds the following section into your web.config file. This section contains the required configuration for your ASP.NET application to use the Azure Cache for Redis Session State Provider.

<sessionState mode="Custom" customProvider="MySessionStateStore">
  <providers>
    <!-- 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 = "5000" [number]
        databaseId = "0" [number]
        applicationName = "" [String]
        connectionTimeoutInMilliseconds = "5000" [number]
        operationTimeoutInMilliseconds = "1000" [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=""
         accessKey=""
         ssl="true" />
  </providers>
</sessionState>

The commented section provides an example of the attributes and sample settings for each attribute.

Configure the attributes with the values on the left from your cache in the Microsoft Azure portal, and configure the other values as desired. For instructions on accessing your cache properties, see Configure Azure Cache for Redis settings.

• host – specify your cache endpoint.
• port – use either your non-TLS/SSL port or your TLS/SSL port, depending on the TLS settings.
• accessKey – use either the primary or secondary key for your cache.
• ssl – true if you want to secure cache/client communications with TLS; otherwise false. Be sure to specify the correct port.
  • The non-TLS port is disabled by default for new caches. Specify true for this setting to use the TLS port. For more information about enabling the non-TLS port, see the Access Ports section in the Configure a cache article.
• throwOnError – true if you want an exception to be thrown when there's a failure, or false if you want the operation to fail silently. You can check for a failure by checking the static Microsoft.Web.Redis.RedisSessionStateProvider.LastException property. The default is true.
• retryTimeoutInMilliseconds – Operations that fail are retried during this interval, specified in milliseconds. The first retry occurs after 20 milliseconds, and then retries occur every second until the retryTimeoutInMilliseconds interval expires. Immediately after this interval, the operation is retried one final time. If the operation still fails, the exception is thrown back to the caller, depending on the throwOnError setting. The default value is 0, which means no retries.
• databaseId – Specifies which database to use for cache output data. If not specified, the default value of 0 is used.
• applicationName – Keys are stored in redis as {<Application Name>_<Session ID>}_Data. This naming scheme enables multiple applications to share the same Redis instance. This parameter is optional and if you don't provide it a default value is used.
• connectionTimeoutInMilliseconds – This setting allows you to override the connectTimeout setting in the StackExchange.Redis client. If not specified, the default connectTimeout setting of 5000 is used. For more information, see StackExchange.Redis configuration model.
• operationTimeoutInMilliseconds – This setting allows you to override the syncTimeout setting in the StackExchange.Redis client. If not specified, the default syncTimeout setting of 1000 is used. For more information, see StackExchange.Redis configuration model.
• redisSerializerType - This setting allows you to specify custom serialization of session content that is sent to Redis. The type specified must implement Microsoft.Web.Redis.ISerializer and must declare public parameterless constructor. By default System.Runtime.Serialization.Formatters.Binary.BinaryFormatter is used.

For more information about these properties, see the original blog post announcement at Announcing ASP.NET Session State Provider for Redis.

Don’t forget to comment out the standard InProc session state provider section in your web.config.

<!-- <sessionState mode="InProc"
     customProvider="DefaultSessionProvider">
     <providers>
        <add name="DefaultSessionProvider"
              type="System.Web.Providers.DefaultSessionStateProvider,
                    System.Web.Providers, Version=1.0.0.0, Culture=neutral,
                    PublicKeyToken=31bf3856ad364e35"
              connectionStringName="DefaultConnection" />
      </providers>
</sessionState> -->

Once these steps are performed, your application is configured to use the Azure Cache for Redis Session State Provider. When you use session state in your application, it's stored in an Azure Cache for Redis instance.

ASP.NET Session State options

• In Memory Session State Provider - This provider stores the Session State in memory. The benefit of using this provider is simplicity and speed. However, you can't scale your Web Apps if you're using in memory provider since it isn't distributed.
• Sql Server Session State Provider - This provider stores the Session State in Sql Server. Use this provider if you want to store the Session state in persistent storage. You can scale your Web App but using Sql Server for Session has a performance effect on your Web App. You can also use this provider with an In-Memory OLTP configuration to help improve performance.
• Distributed In Memory Session State Provider such as Azure Cache for Redis Session State Provider - This provider gives you the best of both worlds. Your Web App can have a simple, fast, and scalable Session State Provider. Because this provider stores the Session state in a Cache, your app has to take in consideration all the characteristics associated when talking to a Distributed In Memory Cache, such as transient network failures. For best practices on using Cache, see Caching guidance from Microsoft Patterns & Practices Azure Cloud Application Design and Implementation Guidance.

For more information about session state and other best practices, see Web Development Best Practices (Building Real-World Cloud Apps with Azure).

Third-party session state providers

• NCache
• Apache ignite

Next steps

Check out the ASP.NET Output Cache Provider for Azure Cache for Redis.