What is the difference between property Cache and OutputCache directive?
Cache is where you can put data - stuff coming from the database, or as the result of an expensive calculation, for example. Anything in cache should be available to all users.
OutputCache caches HTML - an entire page, or the output from a user control.
I suppose you can make a desition in your deep heart that both of them are different.
Most of time the Cache is used as the data or business result store. So you could only process your business logic or against your DB at the first time. You'll find it's very efficient one the process need much time. You can use it in your layers: data lay, business lay and so on.
OutPutCache: It announce the IIS server, proxy, or client to cache the response result. Especially benefit for the dynamic pages. The server will response the cached result to the client once it requested before.
Related
IIS has featured to set "Output Caching" on asp.net sites. I would like to know what is the benefit of this type of caching compared to caching done by our browser.
I am wondering because if our browser has the power to cache content(such as js/css/image), why would .net implement feature such as output caching?
Imagine a page that takes a lot of server-side resources to create -- maybe database calls, heavy computation, etc.
If one user requests that page, and it gets cached by the browser, then the next time that user requests the same page, it will already be on their machine -- so it won't have to be generated by the server or transferred over the network again.
Next, imagine that a second user requests the same page. The fact that a copy of the page was cached by the first user's browser doesn't help. Without output caching, the server will need to perform those time-consuming operations all over again to generate the page.
If the page used output caching, then the results from the first time is was created would be stored in memory on the server, so the cached results could be sent in response to subsequent requests -- which saves time and server-side resources.
Think of it for multiple users, let´s say 100.
Without Output Caching IIS would have to process and generate the page for each user request so the page is processed 100 times.
With Output Caching IIS would have to process the page once (for the first user requesting it), then cache it and return the same version for the other 99 users.
I have an Asp.Net MVC 3 site. The following is the call stack
Web page/jQuery: $(document).Ready(.... Ajax calls... render the page...)
=> MVC Control methods
=> Entity framework 4.1
=> mapped store procedures (SQL Server 2008)
Question:
Where is the best place to implement cache?
How to let the page know that the underline SQL server tables have been updated?
Not sure about the "best" way to do it but one way to do it would be to have an MVC controller action which calls to the db to check and see if the data has been updated. (You can do it by time-stamp.)
The resulting function will then retreive the data from cache or from the server.
http://davidwalsh.name/cache-ajax
The only interesting thing to note however; is that you should make sure that the call to first find out if you can use cached content is faster than not caching content at all.
Try to add caching as close to the source as possible. This way more of your app could gain benefits from the improved speed.
If you control the code that is modifying the underlying tables you could invalidate the cache from there. You could also place a short timeout on your cache. If its a heavily used query caching it only a second could increase speed many fold. Make sure to test the performance gain so that you can tweak timeouts.
For question #2, you may want to look into Query Notifications. Setting everything up is a bit complicated, but that will enable you to do things such as caching until the data in your database has been updated.
One way is to cache rendered views some specified time.
Let's say that you have page that is not updated often. So instead of hitting database on every visit you can store rendered view in cache. This is achieved using OutputCaching - http://www.asp.net/mvc/tutorials/improving-performance-with-output-caching-cs.
Another way could be to store data.
Here again You can cache it for some specified time. In ASP.NET (MVC) it can be achieved using Cache object - http://msdn.microsoft.com/en-us/library/aa478965.aspx.
Cache object let's you specify how long data is to be cached when You put it in cache. For example:
Cache.Insert("key",
myTimeSensitiveData,
null,
DateTime.Now.AddMinutes(1),
TimeSpan.Zero);
Or you can cache until it is 'invalidated'.
Say you have GetCustomers and UpdateCustomer methods. In GetCustomers you check if data is in Cache. If not you hit the database, put it in cache and return. It is in cache until someone calls UpdateCustomer. In that method you write modified customer to database and invalidate data stored in Cache. You can just remove it. That way when GetCustomers is called again it will hit the database and populate Cache again. But remember that Cache has global scope and is accessible for many threads at the same time. You will need some synchronization code around access to Cache.
I am a learner.I am learning Caching in ASP.NET.There are three types of caching in ASP.NET.
1.Page output caching.
2.Partial Output caching.
3.Data Caching.
In Page output caching, all the rendered content of the page saved in Cache and page every time re-execute.
In Partial Output caching, we can apply caching rules on different parts of pages.
But Data Caching, I didn't understand.
Could anyone please explain me Data Caching?
Thanx in advance.
In simple terms data caching is storing data in memory for quick access. Typically information that is costly to obtain (in terms of performance) is stored in the cache. One of the more common items stored in a cache in a Web application environment is commonly displayed database values; by caching such information, rather than relying on repeated database calls, the demand on the Web server and database server's system resources are decreased and the Web application's scalability increased. As Microsoft eloquently puts it, "Caching is a technique widely used in computing to increase performance by keeping frequently accessed or expensive data in memory. In the context of a Web application, caching is used to retain pages or data across HTTP requests and reuse them without the expense of recreating them."
Read more : .NET Data Caching
It is about caching application data (using the Cache class) - persistence of some objects (values).
Is there a built-in asp.net way to conditionally serve pages, for example I want the following logic:
If there is a session data I generate
a page, if there is no session data I
serve the cached page.
I am only interested in knowing about a built-in asp.net mechanism for this. If it does not exist I am probably going to simply cache my page manually and decide whether to serve it or not for each request, based on the session data availability.
I don't think there is built-in support (like varyByParam) for generating fresh output for users with Session Data.
As you suggest, I would recommend manually caching the pages. I would probably determine the user's Session state in the PreRequestHandlerExecute event handler in the Global.asax and then maybe set:
HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
At the risk of karmabombing, I really don't like this approach to caching.
For me if a GET request is made, then a server should respond to that in good faith. Caching at a page level should be controlled by http headers because the primary goal is not to get the redundant request at all - you don't want to allocate server/bandwidth resources full stop.
Caching objects which are resources involved in making up a page I can totally get behind, but I can't see great arguments for caching a page wholesale.
Respect the headers.
You might want to look at the substitution control (Link) new in .NET 2.0, however it might not be exactly what you are after.
I'm using the SqlProfileProvider on one of my websites and in one page I need to fetch the whole list of profiles (it is an intranet).
The method that I use is the ProfileManager.GetAllProfiles(). The problem is that its performance is really bad and it slows down the website considerably.
Therefore, I was thinking of caching the result of the method call in the Application scope as a DataTable (so I could filter/search on it as well).
My problem is that I have several servers running this webapp, and I would like the cache to be in sync. I started using memcached but I was put off by some problems (hence going back to thinking in caching in the Application scope).
So, here are my questions:
Would it be efficient to store the DataTable containing the profiles in the Application object? Or, is it possible to store objects in the Cache and have them available for all clients/browsers?
Is it possible to add a (SQL) Cache Depedency to this cache?
You could cache portions of the web page which will depend on the list of profiles by putting them in a user control and marking it as cacheable. SqlCacheDependency cache policy expiration could be defined as well. As for the cache location, every web server in the farm will have it's own version in memory but using cache expiration will make sure that this version is not out of sync with the data in the DB.
Page or fragment caching is the most effective caching technique because contrary to caching your model (a DataTable or whatever) you don't pay the price of HTML rendering.