I hope that this post has provided you with “a very particular set of skills” to help you debug memory issues. Unfortunately, locating memory leaks can be extremely hard and requires some training and experience. Session state is used to maintain data for an individual user for the duration of their interaction with a web site.
When information is stored in application state, it is available to all the users. For in-proc session state, storing too much in session means high memory usage. For state server and SQL server you have the performance cost of serializing and de-serializing the session data. One solution to this problem is using a weak reference that allows the garbage collector to release the object while the application reference still exists.
The previous object, or value, will be overwritten without a warning. Response code 500 indicates that the server encountered errors in attempting to fulfill the request. Response code 403 indicates that the server understood the request but is refusing to fulfill it. The following example demonstrates the concept of storing view state.
This ” triangular trend” indicates that five concurrent users receive better responsiveness than one concurrent user. The number drops again for 10 concurrent users because it exceeds the pool number and begins to be high enough to burden the server. So if we take a pretty common scenario… You develop an on-line shop application for a customer with relatively few concurrent users. The initial setup is one standalone web server, using in-proc session state, and your application is storing some datasets per user with info about their past orders etc.
- Our tests have demonstrated that the picture is more complex because the InProc mode offers far superior performance in exchange for higher memory usage.
- Add to this the fact that the InProc mode experiences lower TTLB growth rates than other session modes .
- For example, the DataSet object supports serialization, and the DataView object does not.
- You can view the code listing for this component in the sample project that accompanies this chapter.
- Client-side data has no server-side footprint taking up memory between page requests.
- The StateServer mode is often the worst choice you can make for managing session state.
- To start debugging the OutOfMemoryException, I recommend you to look at your application either through the Task Manager or using perfmon.msc.
And by providing access to data that would otherwise require a trip to the server, client-side data reduces both trips to the server and processing on the server (which you’ll appreciate). If the reliability of your session is of utmost importance, then you can implement state management on a cluster of multiple database servers so that no single point of failure exists. In closing out this section, we want to emphasize asp net usage its overall message, which is that session state performance is not as clear-cut as many texts would lead you to believe. For example, many texts brand the InProc mode as a guaranteed scalability killer that should always be avoided on heavily trafficked Web sites. Our tests have demonstrated that the picture is more complex because the InProc mode offers far superior performance in exchange for higher memory usage.
Memory Leaks In Net Applications Yes
It’s surprising how often developers forget to do this but it’s probably the single most important responsibility developers have in resource management. Any application that uses unmanaged resources will drown at scale if the clean-up code isn’t being called properly. For example, the.Net garbage collector is supposed to take care of memory management but it only releases memory that is unreachable. If an application still has a reference to an object then it won’t be released. Therefore, there’s still plenty of scope for writing a leaky application in the .Net framework. Developers do need to be aware of what’s going on under the hood as there are a number of common traps for the unwary.
Looking at the top rows is a good indicator of what is causing a leak. Unlike Task Manager and Perfmon, memory profilers are tools to help you find the root cause of a memory problem or memory leak. There a lot of useful tools out there like JetBrains dotMemory and ANTS Memory Profiler.
Data used across multiple pages by a single user (data you’d normally stuff in the Session object on the server). Throwing everything into the Session object and using a Session server isn’t the answer to any of these problems. There are a wide variety of tools for caching data, with each of these tools solving a particular problem. If you’re not taking advantage of all of them — and understanding when they’re appropriate — your site won’t be performing as it should.
The TTLB numbers are similar for Off, StateServer, and SQLServer modes. However, the numbers are lower for InProc mode by up to a factor of two. This number becomes important when the Web server is under heavy load. A lower TTLB number translates into less latency ”that is, more requests serviced per second. The testing results indicate this, as shown in Table 4-2, which presents Group A average request rates for each of the session state modes. Processor utilization is another important metric because it indicates whether your hardware is a limiting factor to your application’s scalability.
We ran the Group B tests because we could not otherwise generate memory usage numbers for different session state modes. The InProc mode is an excellent choice if the session items are modest in size and you are not concerned about potentially losing session items and having to re-create them. E-commerce applications, for example, cannot afford to lose session data.
I have a session variables and I would like to know how much they memory they consume then multplied with my projected user load. I am a London-based technical architect who has spent more than twenty five years leading development across start-ups, digital agencies, software houses and corporates. Over the years I have built a lot of stuff including web sites and services, systems integrations, data platforms, and middleware. My current focus is on providing architectural leadership in agile environments.
Overview Of Session Management
We were unable to generate memory usage numbers for Group A tests because ACT could not bind to the remote Memory counter on the Web server . However, ACT has no problem binding to the Memory counter on the same server. As a workaround, we ran an alternative set of tests on a single server . Before proceeding, we should point out that, in reality, you would likely not design a Web application to have tens to hundreds of session-stored data sets. The ACT tests represent unusually stressful conditions that would not likely be duplicated in the field because you would make a different design decision to avoid this situation. You can share session items across multiple Web servers and potentially persist them until the service is stopped or the session item is explicitly removed.
We are not attempting to explain the numbers away, but we are simply presenting the TTLB test results so that you can keep them in mind when evaluating the memory usage results. The TTLB numbers shown in Figure 4-4 exhibit subtle differences, except for InProc mode, which experienced the lowest TTLB numbers. This indicates that the InProc mode can service a superior number of requests and remain more responsive than other session modes.
Caching ensures that once you retrieve the data, you keep it at the client to eliminate later trips. Figure 4-6 shows the Group B normalized TTLB values, based on 100 requests. The SQLServer and StateServer modes experience much higher TTLB values, compared to the InProc and Off modes, by up to two orders of magnitude. This difference may reflect the greater processor burden on the single server. Simply put, with more demands on the processor, the SQLServer and StateServer modes suffered because they are more dependent on processor availability.
One of the knocks against classic InProc session variables is that they are scalability killers. They exhaust server resources rapidly as the number of concurrent users increases. In fact, session variables continue to use server resources, even if the user is not actually storing any session-specific information.
Using a date allows me to reduce checking on the client by not requesting the data if I’ve updated local storage within, for instance, the last hour. If you decide on using the StateServer mode, then you need to start the ASP.NET State Service on one of the servers in the Web farm. You must designate only one server in the Web farm for managing session state because you are proceeding on the assumption that there is no fixed redirection of requests in the Web farm. The advantage of this approach is its flexibility in being able to manage state for all servers in the Web farm. However, the disadvantage of this approach is that it creates a single potential point of failure. In exchange for flexibility, you run a higher risk that the State server may fail and be completely unavailable for all servers in the Web farm.
Finally, select the process you want to monitor in the Instances of selected object list and click the OK button. For any data that’s shared among users, caching data helps ensure that you have only one copy of the data soaking up memory, instead of a copy for each user. Even for data kept on a per-user basis, using a combination of the Cache and the Session objects can reduce demands on your Web server’s memory. In addition, the Cache is designed to handle every possible case — you can improve caching solutions with business-specific code. My next step is to determine if the local data is out of date; if it isn’t, I’ll retrieve the latest version of the data. The simplest value might just be the last retrieved date, but an alternative is to use the timestamp value from a database row.
On subsequent requests, the code compares the current textbox values with the values in view state. If they are the same, then the code attempts to retrieve the DataSet from the Session object. If they are different, then the code executes a fresh database request. To provide for the use of application state, ASP.NET creates an application state object for each application from the HTTPApplicationState class and stores this object in server memory. The ASP.NET application is the collection of all web pages, code and other files within a single virtual directory on a web server.
Read And Write To The Users Session
Let us keep a counter, which is incremented each time the page is posted back by clicking a button on the page. Request Metrics records how real usersexperience your website and shows you simplified metrics and alerting. We will use a distributed session using Redis because we have existing Redis infrastructure and we don’t want a complex load balancer added to the mix. Naturally from here the next step is to find out what is on the large object heaps. Join Bytes to post your question to a community of 470,972 software developers and data experts. I don’t want this to be an ad for .NET Memory Profiler, so check out their documentation for the full picture of how to profile memory in your .NET programs.
About Request Metrics
Anybody developing with C or C++ will be only too familiar with the insidious effects of memory leaks. Simply put, a memory leak occurs when an application doesn’t free up memory that it has finished using. Memory leaks are bugs with unpleasant, slow-burning consequences that can take some time to manifest themselves.
The Off mode uses the least amount of memory, which is to be expected. The SQLServer mode falls somewhere in between, although it is interesting to note that its growth curve in memory usage is steeper than for other modes. It is unfortunate that ACT could not generate meaningful numbers with more than 10 concurrent browsers because it would be interesting to see where the trends continued . The first time that the page executes, it retrieves a DataSet directly from the database. This DataSet gets bound to the DataGrid and then assigned to a Session object. In addition, the search parameters are persisted directly to view state so that they are available for comparison purposes.
State buckets such as session caches encourage developers to create unnecessary and long-lived memory dumps. Over-aggressive caching can start to resemble to symptoms of a memory leak. Although the details of memory management may be largely hidden from developers, they still have a responsibility to protect finite memory resources and code as efficiently as possible.
One approach is to persist session information in hidden fields or in the Uniform Resource Locator querystring. In these cases, neither the Web server nor the client requires direct session management support. As an example of how to use client-side data for temporary storage, assume a user’s attempting to buy some product on your site. Or you could store the data in session storage and, on a page-by-page basis, embed it in hidden fields to get it back to the server when needed for server-side processing. In the “Understanding Session State Modes” section, we examine the various ASP.NET session state modes in detail.