C# - Application_End() Cannot Access Cache Through HttpContext.Current.Cache
Dec 12, 2010
I want to be able to maintain certain objects between application restarts.
To do that, I want to write specific cached items out to disk in Global.asax Application_End() function and re-load them back on Application_Start().
I currently have a cache helper class, which uses the following method to return the cached value:
return HttpContext.Current.Cache[key];
Problem: during Application_End(), HttpContext.Current is null since there is no web request (it's an automated cleanup procedure) - therefore, I cannot access .Cache[] to retrieve any of the items to save to disk.
Question: how can I access the cache items during Application_End()?
I have use Nhibernate in my MVC Project by me known, Nhibernate have cache on Session and Object. now, I want use HttpContext.Current.Cache (system.web) for cache data something in project. my code same that have problem, haven't it. and that's right or wrong.
During Application_End() in Global.aspx, HttpContext.Current is null. I still want to be able to access cache - it's in memory, so want to see if I can reference it somehow to save bits to disk.
Question - is there a way to reference cache in memory somehow when HttpContext.Current is null?
Perhaps I could create a global static variable that would store pointer to cache that I could update on HTTP requests (pseudo: "static <pointer X>" = HttpRequest.Current) and retrieve a reference to cache through that pointer in Application_End()?
Is there a better way to access Cache in memory when there is no Http Request is made?
As per title. I want to be able to save some data in a cache object but this object must be available to all users/sessions and can expire.What is the best method to achieve this in a asp.net web app?
Last night I wrote up my first IHttpModule to do some request processing. I'm using a regular expression to inspect the raw url. The IHttpModule will be called on every request, so it seems reasonable to do some sort of caching of the regular expression object to prevent creation of it on every request.
Now my question... what is better: use the HttpContext.Current.Cache to store the instantiated object or to use a private static Regex in my module?I'm looking forward to the reasons why. Just to clarify: the regex will never change and thus always be the same thing.
Apart from blocking other threads reading from the cache what other problems should I be thinking about when locking the cache insert method for a public facing website.
The actual data retrieval and insert into the cache should take no more than 1 second, which we can live with. More importantly i don't want multiple thread potentially all hitting the Insert method at the same time.
The sample code looks something like:
public static readonly object _syncRoot = new object();
We have a wfc layer that wraps the business classes and database access and use a client that lives on the database layer. Amongst our group we are attempting to form standards. Some want to have the client call the web method and pass the page they are requesting and the page size. Pass that to the database and then page in SQL Server use RowNum.Some want to cache the full list of objects in http cache on the service tier and page in memory. They concern here is memory use on the server.
Which would be best for a medium number of users with potentially large number of records to manage (say 30K) Is it better to cache them all in memory and work from there or page at the database as the application scales?
Since I don't want my sessions to be removed unless the session has been abandoned either via code or Session Timeout...For eviction, I would think "None" and for expireable, I would think False.I have tested and calling Session.Abandon does remove the object from the cache. I have also tested to see if by extending my session, the session object in cache is also extended. This does seem to work the "correct" way.
We have a data driven ASP.NET website which has been written using the standard pattern for data caching (adapted here from MSDN):
public DataTable GetData() { string key = "DataTable"; object item = Cache[key] as DataTable;
[code]...
The trouble with this is that the call to GetDataFromSQL() is expensive and the use of the site is fairly high. So every five minutes, when the cache drops, the site becomes very 'sticky' while a lot of requests are waiting for the new data to be retrieved.
What we really want to happen is for the old data to remain current while new data is periodically reloaded in the background. (The fact that someone might therefore see data that is six minutes old isn't a big issue - the data isn't that time sensitive). This is something that I can write myself, but it would be useful to know if any alternative caching engines (I know names like Velocity, memcache) support this kind of scenario. Or am I missing some obvious trick with the standard ASP.NET data cache?
we have so many parameters that the cache key is several hundred characters long. is there a limit to the length of these cache keys? Internally, it is using a dictionary, so theoretically the lookup time should be constant. However, I wonder if we have potential to run into some performance/memory problem.
I've got a web application that runs of a state server. It looks like soon it may need to distributed and there will be two web servers behind a load balancer.
This works great for session state but my next challenge is Cache
My application leverages heavily of cache. I understand ASP.Net 4.0 will be offering more here but nothing much has been said about the how too.
There are two challenges that I face
1). Each webserver will have its own copy of cache whereas it would be more efficient to put this to a third server the same as session state is put to state server.
2). The real challenge is keeping cache in sync if a simple dataset derived from the database is changed my code dumps that cache item and reloads the cache. That's all well on one webserver but webserver number two wont know to drop that particular cache item and reload it. This could cause some unexpected problems in the application.
For scenario number 2 I could attempt to do some smart coding so server number two knows to dump the cache and reload it.
My guess is someone else has already been here before and there's probably a better implementation approach rather than writing extra code.
Does anyone know how I could achieve the goal of keeping Cache in sync between multiple webservers or even better farm Cache management to another server?
I need to enable caching in my asp.net application, but I do not want to use the webserver's memory for holding cache objects. If I add the page directive for output caching will the page be stored in the asp.net cache object?
I have a static class with serveral static methods. In these methods, I'm trying to access the current thread's context using HttpContext.Current. For example:
var userName = HttpContext.Current.User.Identity.Name;
However, when I do that, I receive a NullReferenceException, the infamous "Object reference not set to an instance of an object."
Im building a image gallery which reads file from disk, create thumbnails on the fly and present them to the user. This works good, except the processing takes a bit time.
I then decided to cache the processed images using the ASP .NET Application Cache. When a image is processed I add the byte[] stream to the cache. As far as I know this is beeing saved into the system memory. And this is working perfect, the loading of the page is much faster.
My question is if there are thousands of images which gets cached in the Application Cache, will that affect the server performance in any way?
I am building a web application using asp.net (c#) and lingtosql. When I perform update operations on my db I update my classes. I use gridview to bind to update information. When I relay solely on the database the page's take very long to load. When I relay solely on the cache, I have old data. What workarounds do I have for have asynchronous cache updating, yet not overload the database with endless requests (I'd like to update the cache only if there has been a change in the database itself, and perform the update operation asynchronously).
You know I have the way to Cache the data I've got from the SQL Server over data caching. In addition I can output cache web user controls.Whats about a web user control contains data from a SQL database? Does it make sense to cache the data and also cache the control?What is the best solution for the combination of these two components?
I have a server control that I developed which generates navigation based on a third party CMS API. Currently I am caching this control using the PartialCaching attribute. The CMS uses cache key dependencies to invalidate the cache when a user makes an edit, however in the case of my server control it does not get invalidated and the updated navigation will not show up until the cache expiration set by the PartialCaching attribute.Here is my two part question:
What is the proper way to programmatically cache a server control, without using the PartialCaching attribute, and adding a cache key dependency?
Is it possible to continue to use the PartialCaching attribute and add a cache key dependency?
In ASP.NET, is there any reason not to make a set of functions that Add/Remove/Get from the Cache object Static?Get() - just gets the item, no reason not to be staticAdd(), Remove() - I've read that adding/deleting into the cache has it's own internal locking mechanism, so they can be static without me creating my own lock(){} wrapping.
Suppose I have two threads(Thread1, Thread2) where the threads are accessing the cache for a given object such as in the code below nearly at the same time:
Dim expensiveToGetData = Cache("ExpensiveDataKey") If ExpensiveToGetData is nothing then 'because the cache has expired ExpensiveToGetData = LoadExpensiveDataFromDataSource() Cache("ExpensiveDataKey") = ExpensiveToGetData end If ProcessExpensiveData(ExpensiveToGetData)
Isn't it possible for both threads to load the cache because they both requested data from the cache that was nothing/expired? I've run some tests on a local machine and it seems that the cache is being loaded more than once. Is this a normal pattern?
How can I access the cache of one web application/domain from another web application/domain?Here is my scenario. I need to verify/check the existence of a certain object in one web application/domain's cache from another web application/domain.
I have a music related ASP.NET web site which caches a lot of static information from the database on the first request.Sometimes, the application is reset and cache is cleared while the application is on heavy load and then all http requests go to the database to retrieve that static data and cache it for other requests.
How can I ensure that only one request go to the database and cache the results, so that other request simply read that info from cache and not needlessly retrieve the same info over and over again.Can I use thread locking? For example, can I do something like lock(this) { db access here }?
