Response code 403 is frequently returned for higher numbers of concurrent browsers. We do not consider performance numbers meaningful unless greater than 97.5 percent of the requests are fulfilled successfully. For this reason, in the following performance test, we ignored all test runs with greater than 10 concurrent browsers. However, there needs to be some technique to store the information between requests and to retrieve it when required.
The memory usage for the ASP.NET process is very high (800MB – 1GB), sometimes resulting in out of memory exceptions or unwanted recycles of the process. Remember that strings are stored internally as unicode (2 bytes/char). Next, turn your attention to the topic of application state management. Session objects provide a straightforward application programming interface that is easy to code against.
Clearly, there are performance implications when you require a server to manage session information. This task is an additional burden on the server and requires it to allocate valuable resources, both in terms of memory and processor utilization. The key is to pick a session state mode that provides the best session management for your application with the lowest overhead. That is, you must pick a mode that offers the optimal balance between performance and reliability for your particular state management requirements. The Group A tests represent better testing practices because the architecture spreads the processing burden between multiple servers.
Next, we’ll create a sign-up flow for users to create their accounts in the first place. For each object, we print out the session variable name at offset 0x4, the object at offset 0x8 and the size of the object. To find out how much is stored in them we can use a for each loop using the method table for InProcSessionState from above and run ! That most of our memory is in the large object segments, i.e. objects over bytes.
However, this abstraction does not make applications immune to memory leaks. The promise of garbage collection and abstracted memory management does lull many .Net developers into a false sense of security. All the client-side programming in the world isn’t going to completely eliminate trips to the server, however. Figure 4-7 shows actual memory usage by session mode where memory usage is defined as the percentage of committed bytes in memory . This is an actual measure of memory usage on the server, and it reflects the level of burden that each session mode places on available server memory.
However, other applications can use Session objects to reduce redundant database calls that would return duplicate information. These applications can easily re-create session items if they are lost. Based on our limited data set, it is useful to look at relative growth rates in TTLB, as shown in Figure 4-5. The TTLB is normalized for each session mode, based on one concurrent user.
For this post, I’ll use .NET Memory Profiler, which I have used heavily in the past. BTW, as an elmah.io customer, you will get a 20% discount on .NET Memory Profiler. That data can be updated on the client when the user changes it, and stuffed into hidden fields to be returned to the server when needed for server-side processing. This read-write property gets or sets the timeout period between requests before the session is terminated . If the attribute value is “True,” then either a new session will be created or an existing session will be used. If the value is “False,” then no new session will be created and no session values may be accessed on the page.
This information i.e., the current value of all the controls and variables for the current user in the current session is called the State. Each InProcSessionState object has a dict member variable that holds the actual session objects in its _entriesArray. The root chain tells us that this particular Int32 array is rooted in cache, more specifically in the InProcSessionState object, indicating that it is stored in in-proc session scope. In ASP.NET 1.1 as you probably know, there are 3 different locations to store session objects. The garbage collector is not responsible for cleaning up the stack as any space reserved is automatically cleaned up when methods return. If an application creates worker threads for background tasks and does not terminate them properly then the memory that is used by the thread is never released.
- Serialization is the process that allows an object to be represented in an XML document or as a binary stream.
- If you hold onto a variable unnecessarily then you are preventing the garbage collector from freeing up memory as quickly as possible.
- But then, consider that it services a far greater number of requests than the other modes.
- Note Some developers prefer to create custom session management code rather than using the Session object.
- If you must assign a data object to a session, then use a disconnected object such as a DataSet or DataView.
- Take for example a dataset, this will normally be serialized with the binary formatter (unless you don’t create your own dataset surrogate) into an XML format.
This read-only property gets the unique session ID used to identify the session. The bottom line is that only you can decide which approach is best for your Web site. There is no set of test numbers that can ever tell the definitive story, and we ask you to keep this in mind and to possibly be inspired to extend our testing with your own.
Episode 16: Using Redis For Distributed User Sessions In Asp Net Core
For that, either we put all the common data in each request, or we put key in request to store the data on the server against each key. The session state object is created from the HttpSessionState class, which defines a collection of session state items. When a user connects to an ASP.NET website, a new session object is created. When session state is turned on, a new session state object is created for each new request.
Suddenly the application gets more popular and a larger company wants to use it. It needs to work on a multi-server web farm, so you move to SQL Server session state. There are of course pros and cons of each but no matter which one you use, you should be careful with how much you store in session state if you want your application to be scalable.
Blazor Mvc Revives Old Tech For Modern, Red
Session items must support binary serialization to work with the StateServer mode. Popular objects such as the DataSet object do support binary serialization. Session items use up server memory and may negatively impact the scalability of the application. There is actually a dual challenge to retaining and providing session-specific information. On the one hand, there is the challenge of how to retain and procure the information. And on the other hand, there is the challenge of how to do it quickly .
An especially popular approach is to retain all session information in a dedicated database, using the session ID as a primary key for referencing the information. This approach is not without its performance implications because database calls are slower than pulling data from memory. But the performance hit is worthwhile given that data is guaranteed to be available, especially from clustered SQL Servers, which are highly available. We have a site being setup on IIS 6 and was told not to use sessions too much as the server had limited application memory . My understanding (based on unix/linux apache hosting and lighttpd) was that session data etc was stored in actual files.
About Request Metrics
These numbers may not look very different, but they can translate into a dramatically different number of total serviced requests. For example, over the course of the 35-second testing interval with 10 concurrent users, the Off mode serviced 603 total requests, and the InProc mode serviced 833 total requests. The StateServer mode is often the worst choice you can make for managing session state. The cost of marshaling data across process boundaries is high, even if the size of the data is small.
Analyzing Session State Performance
Those tools include some new, standards-based technology at the client, effectively integrating the tools ASP.NET gives you, and exploiting some new Microsoft technology. You should not store objects, such as the DataReader, that maintain open connections to a database in Session objects. If you must assign a data object to a session, then use a disconnected object such as a DataSet or DataView. This read-only property gets a collection of the keys of all values stored in the session. It potentially impacts application scalability when session items are large and/or the number of session reads and writes is high.
However, Microsoft recommend against using this as a default solution to memory management problems. Ultimately, more robust management of event subscriptions is the preferred approach to avoiding leaks through lapsed asp net usage listeners. While leveraging client-side data is dependent on your willingness to write client-side code, the benefits are huge. Client-side data has no server-side footprint taking up memory between page requests.
If a server crashes or becomes unavailable, then the client will be routed to another server, which will have no record of their session information. For this reason, you may want to consider using centralized session state management. If the session mode is StateServer, then you can only assign objects that support binary serialization.
Of course, there are other considerations that go into choosing a session state mode. For example, if you must persist session state to disk or manage it in a Web farm, then InProc mode will not meet your needs, no matter how good or bad it may be. The previous section described the advantages and disadvantages of each session state mode and discussed the optimal usage scenarios for each mode. Your goal must be to stay ahead of the curve by designing your system to manage its expected loads as efficiently as possible. Ultimately, performance tuning is important because it allows your system to handle higher loads without a redesign or without having to purchase bigger, more expensive hardware.
Read And Write To The Users Session
This session state object becomes part of the context and it is available through the page. When the client disconnects from the server, the ASP.NET engine discards the page objects. This way, each web application can scale up to serve numerous requests simultaneously without running out of server memory. In proc which stores session variables in the cache, State server which stores it in the state service and finally SQL Server. Ultimately you have finite resources so you should get used to the discipline of only using memory when you have to.
Also, make sure to check out the alternative products mentioned above. All of them have free trials, so try them out and pick your favorite. The common language runtime cannot allocate enough contiguous memory. After previously discussing permutations, Dr. James McCaffrey of Microsoft Research uses step-by-step examples and full code presentations to explore combinations. Crafting a caching strategy is critical to building effective Web apps. It’s only possible when you know what options are available and how to integrate them.
In single server situations it’s simple to set up because ASP.NET supports in-memory session out of the box. In-memory sessions stop working as soon as there is more than one server. Most production environments have more than one server so the session issue needs to be dealt with.
But then, consider that it services a far greater number of requests than the other modes. Increased memory usage may be a small price to pay for the far greater number of requests that you can service, compared to other session modes. Add to this the fact that the InProc mode experiences lower TTLB growth rates than other session modes . The InProc mode suddenly appears to be an attractive option for managing session state. This trend indicates that the Off mode experiences the greatest growth in TTLB as the number of concurrent users increases.
If you must access Session data from multiple servers, then SQLServer mode is often a better choice. If you track the memory usage for the application you’ll see it slowly moving up with each new thread as memory on the Stack fails to get released. To start debugging the OutOfMemoryException, I recommend you to look at your application either through the Task Manager or using perfmon.msc. Both tools can track the current memory consumption, but to get a better overview over time, perfmon is the best.
It is automatically maintained across posts by the ASP.NET framework. Join Sam the Performance Sloth’s newsletter for fresh web performance reviews, ideas, and tools. In this specific case the .foreach might seem like overkill but it’s good to know how to do it for larger collections. We can either dump out these objects individually or we can let the debugger do the work for us. Once we get here a search through the code for session assignment, focusing on Int32 arrays may be in order.
As these larger objects are allocated and freed, gaps inevitably start to appear in the large object heap. Memory use becomes much less efficient and under certain circumstances this can cause “out of memory” exceptions as the heap becomes hopelessly fragmented. This may seem straightforward, but it also applies to any objects that are indirectly referred to by a static field. If you don’t pay attention to indirect references then you may get an ever-increasing chain of object references building up. They will hang around for ever because the root reference at the start of the chain is static.