The next line of code retrieves the stored value from the Session object. It then writes this value via the ‘Response.Write’ method back to the client. The other way is to use an object called a “Session Object.” The Session object is available throughout the lifecycle of the application.
This indicates the same worker process within the web garden has served us the page consecutively. This would be same result as if IP affinity were configured for the web garden or web farm. If we continue to refresh the page, we would expect the same magical spell to display with the view count incremented accordingly. Consider the case where the above C# ASP .NET web application has grown to the point where a single web server is no longer sufficient to serve all requests.
SQL Server is an enterprise-class database solution optimized for managing, storing, and retrieving data quickly and efficiently. In a clustered environment, SQL Server can be configured to failover. For example, when the clustered production SQL server fails, a backup can take over. When ASP.NET is configured to use state server for out-of-process session, it uses a TCP/IP address and port number to send HTTP requests to the state server . We recommend SQLServer for out-of-process session state because it is just as fast as StateServer and SQL Server is excellent at managing data. Furthermore, ASP.NET can communicate with SQL Server natively (meaning internally, using the System.Data.SqlClient libraries), and SQL Server can be configured to support data failover scenarios.
Web farms provide a necessary solution for offloading and expanding high-traffic and demanding C# ASP .NET web applications. When not available during development, web gardens may be utilized to help simulate the demands of a web farm environment by providing multiple worker processes on a multi-core machine. Configuring the web application to use OutOfProc session in a web garden scenario, can help resolve issues prior to application deployment on a web farm. Further abstraction and migration to web clouds can provide on-demand web application sizing and scalability. StateServer session state stores data within a 3rd-party process, aspnet_state.exe.
The process is shared by multiple worker processes and web servers and servers as a memory-based database for holding session state data. StateServer serves data over a TCP port, typically port 42424, and allows incoming requests from outside servers. However, a drawback is that the usage of memory can grow over-time, potentially over-using the available server resources. Upon executing the web application, now a single magical spell is created and stored within session. Subsequent page refreshes continue to display the same magical spell and increment the view count each time. Since our web application is now loading session state from the 3rd-party StateServer process, all of the worker processes within the web garden can access the same, synchronized, session state data.
How To Wrap The Asp Net Session State
When the page completes execution, the session state module connects to the state store, writes the session state data if it changed, and unlocks the session data. Variables stored in a Session object hold information about one single user, and are available to all pages in one application. Common information stored in session variables are name, id, and preferences. The server creates a new Session object for each new user, and destroys the Session object when the session expires.
- In particular, we’ll focus on implications of Session State and potential solutions for scaling session across multiple processors and servers.
- This would be same result as if IP affinity were configured for the web garden or web farm.
- The variable is persisted in the web server’s memory and held for the duration of the timeout value, specified in the web.config.
- As shown in the above screenshot, the 3rd refresh of the page results in a new magical spell being created, with a fresh view count of 1.
- It’s important to note that objects stored in the session must be serializable.
- 2) Normally this should be locked, but IMHO it is not necessary in this case.
If you must use SQL Server credentials, ASP.NET 1.1 supports storing credentials securely. ASP.NET session state supports two out-of-process options, state server and SQL Server . Each has its own configuration settings and idiosyncrasies to contend with, such as managing stored types. The ASP.NET State Service is recommended for medium-size Web applications. For enterprise-size or highly-transactional Web applications, SQL Server is recommended. If the account has the necessary permissions, integrated authentication should be used.
Throw Another Web Server Into The Mix
It’s because ASP.NET session state is stored in the memory space of an appdomain. Important Using the SessionID as a key for user data is not recommended. The SessionID is randomly generated, and session data—as well as session IDs—do expire. Additionally, although a SessionID might be generated on each request, a SessionID is set only when a Session value is set server side. This means that if no session values are set server side, new SessionIDs are issued on each request. The mode attribute needs to be SQLServer, and the sqlConnectionString attribute must point to a server running SQL Server that has already been configured for ASP.NET SQL session state.
The majority of C# ASP .NET web applications are often developed with the intention of running in a single web server environment. They’ll often take advantage of ASP .NET’s Session State to store variables and data on the server, per user. As an ASP .NET web application grows in usage and popularity, scalability issues may arise, as the single web server is brought to its maximum capabilities.
To configure SQL Server to support ASP.NET session state, either open the InstallSqlState.sql file in isqlw.exe , or use the command-line tool osql.exe. To use SQL Server Query Analyzer, from the Start menu, navigate to \All Programs\Microsoft SQL Server\Query Analyzer. Note that clustered SQL Server scenarios are not supported out of the box for ASP.NET session state. To enable the clustering or replication features of SQL Server, session data must be stored in a non-tempDB table. These events can be programmed in either global.asax or within an HTTP module. We often get asked why we store session data using tempdb vs. a table.
How To Enable Session In C# Asp Net Core?
The original design goal was to ensure that SQL Server state was fast, and because tempdb is memory-based, SQL Server state would be very fast. However, since SQL Server is so optimized, storing the data in non-temporary tables proved to be nearly as efficient. (SQL Server is super aggressive about keeping frequently accessed data in memory.) In retrospect, using tempdb probably wasn’t necessary. Important Don’t use the Session_End event; it can be called only for sessions created in the InProc mode. The event is not raised for sessions created in one of the out-of-process modes when sessions are abandoned.
When you apply this strategy for optimizing out-of-process session, you get fewer requests to the out-of-process session store, which increases the scalability and throughput of the site. Once the server designated to run the state server has been properly asp net usage configured, it is simply a matter of starting the Windows service. The service can be started from either the command line or the Microsoft Management Console for Services. Important Use in-process session state if you have only a single server.
As mentioned in the web farm topic above, sticky-sessions can be utilized as a quick solution for Session state. By directing incoming requests to the same web server throughout the session, data will always be pulled from memory on the same physical web server. Compatibility and support for configuring sticky sessions can be located within the load balancer settings or web cloud configuration, if available. As shown in the above screenshot, the 3rd refresh of the page results in a new magical spell being created, with a fresh view count of 1.
Session Data In A Web Farm
Multiple requests can read data simultaneously when the session isn’t locked. If the session is locked, read requests are blocked until the write lock is released. This locking strategy guarantees that the Session object with which the user is interacting is always an accurate reflection of the data. If you attempt to build a site that uses frames, and each page within a frame requires session state, the pages will execute serially. You can configure session state to be read-only on a page-by-page or even application basis. Configuring a page to use session data in a read-only manner allows the page to be requested without locking the session data and prevents serialized access.
Outofproc Session State
Often, if a web application performs well in a garden scenario, it will typically be easier to migrate to a web farm. Session stores the data in the dictionary on the Server and SessionId is used as a key. It is possible to remove a session variable with the Remove method. You can also store user preferences in the Session object, and then access that preference to choose what page to return to the user. A session ends if a user has not requested or refreshed a page in the application for a specified period.
Asp Net Session Management Tutorial
The first line of code takes the value of the Name textbox control and stores it in the Session object. By specifying the code of Session[“Name”] , we are giving the property a name called “Name.” By specifying a name for the property, it becomes easier to retrieve it at a later point in time. In our example, we are going to use the Session object to store the name entered in the name textbox field in the page. We are then going to retrieve that value and display it on the page accordingly. This stores the value in a Session object and the ‘key’ part is used to give the value a name.
Important Use integrated authentication rather than store SQL Server credentials within your configuration file. If you decide to use SQL Server user names and passwords, do not use the system administrator account. Instead use an account that has only the necessary access to the database object required for the operations .
However, a down-side to IP affinity is in not taking full advantage of the web farm capability in fully distributing and routing all requests and sessions. In general, web gardens use more resources than typical hosting environments. They may also be slower in performance and add unnecessary complexity. Another scenario may involve unreliable web application processing, which could cause a worker process to halt or freeze. In both cases, a web garden could offer a solution by offloading the single worker process and distributing incoming requests amongst the workers in the application pool. The locking mechanism implemented is a reader-writer lock using the ReaderWriterLock class.
Each tier of the solution can be expanded and grown as necessary to serve the users’ needs. The same principle can be applied to migrating the two tiers to web clouds or even multiple web services on multiple tiers, complexity aside. For this example, we’ll create a basic type object, which will be stored and retrieved from the Session. We’ll use this object to test the distribution of the OutOfProc session state and proper performance across the web garden/web farm. It’s important to note that objects stored in the session must be serializable.
When Does A Session Start?
It is common to abstract a layer of the web application design for handling data processing and database activity. This layer can be abstracted further into a WCF web service layer, hosted and executed within its own web server, separate from the main web application’s web server. Taking this one step further, the main web application can execute on its own web farm and load balancer, while the WCF web service executes on its own web farm and load balancer.
In particular, we’ll focus on implications of Session State and potential solutions for scaling session across multiple processors and servers. We’ll also view an example web application utilizing Session to examine the differences of running InProc versus OutOfProc in a web garden/web farm environment. InProc – Session state will be lost if the worker process (aspnet_wp.exe) recycles, or if the appdomain restarts.
All HttpHandlers that implement IRequiresSessionState are locked to one request per session. They enter the lock in SessionStateModule.BeginAcquireState() and leave it in SessionStateModule.OnReleaseState(). If the SessionVariable value is null, and somebody tries to read it (GetInternalValue), while another thread is trying to set a new value.
C# ASP .NET web applications developed for compatibility with a multi-server environment can often be utilized in both web farm and web cloud environments. A web farm is a hosting environment consisting of multiple web servers. The web servers are usually tied together with a load balancer, which routes incoming requests amongst the servers within the web farm. Tip For ASP.NET 1, configure SQL Server for mixed-mode authentication by adding the ASPNET account enabled for the necessary SQL Server permissions for ASP.NET session state. (The ASPNET account is the user that the ASP.NET worker process runs as.) For ASP.NET 1.1 running on IIS 6, configure SQL Server for mixed-mode authentication by adding the NT AUTHORITY\NETWORK SERVICE account. Upon refreshing the page (or clicking the Read Session button to re-load with AJAX), the same magical spell is loaded , this time with the view count incremented to 2, as expected.
The agent runs a periodic job to purge expired sessions from the database. The main drawback to sticky-sessions for managing InProc session state is that it opens the individual web servers to potential overload. This results in a less scalable solution when compared with distributed session state or session-less web application architectures. In the above example, Session state is first accessed to load an ID variable.
Declare and initialize the session variable in a static field or property in a third class – you could call it “SharedState”, for example. As you can tell in the above execution, running as InProc in this environment is less than ideal. However, we can solve this by re-configuring the web application’s web.config to utilize OutOfProc StateServer storage. For purposes of this example, the MVC Razor markup code has been included above.