I'm building a site in Symfony 2.0 that has a fair amount of AJAX, which builds page content with data it gets from an API, like: http://mysite.com/api/pictures/list
Data is handled using Repositories, which are sometimes used in page code so that string of images you see might come from the controller using the PictureRepository, or via Ajax using the API which accesses the PictureRepository.
I'd like to use Memcached to ease the database load, but am not sure where to put the caching code. Is it best to cache the database result, or the API result? Or is the difference negligible? Having the memcached logic inside the Repository would mean writing the code once (regardless of whether it's accessed via the API or directly), but it seems like it would also make sense to avoid accessing the Repository whenever possible.
Thoughts?
My opinion is that memcached should be used for session storage.
For your purposes you should better think about using of Varnish as http cache.
After that, you can configure your application use ESI.
At least, that is how we do it in our applications ;)
Related
We have an environment with a vendor deployed application to several front ends on it. It makes heavy use of the ASP .Net storage (Session, Application, and Cache). Problem is with the load this environment quickly brings IIS to it's knees with the amount of data it's trying to keep in memory.
The solution we are trying to go with is to override the storage mechanism and implement our own. (Specifically a Redis server to manage the storage)
We have implemented their cache interface and set up Microsoft.Web.Redis.RedisSessionStateProvider in the web.config to manage the session. That part all works fine. The problem is that the caching inside the vendor application does not always use their provided interface. Decompiling the dll and examining dump files show that there are several instances of them directly calling (for example):
HttpContext.Current.Cache.Insert(...) and HttpContext.Current.Application[...] = ...
Is there any way we can override the HTTPContext* calls so that they'll use Redis to cache instead of the Asp .Net application storage?
When it is a "3rd" party which uses HttpContext.Current you probably have no chance to change that behavior.
Is this other application running within your context (do you control the app domain). Or is it a standalone application?
I once tried to change HttpContext.Current.Cache for unit testing and ended up mocking the whole HttpContext because it was so very internal somewhere in the Microsoft stack.
All this is pretty hard to do, not really recommended and can lead to all kinds of other errors.
In short, don't use HttpContext.Current.Cache. Use something you can inject.
In general, libraries should never use that static context.
It is much more flexible to have abstractions + DI for those kind of things...
For caching, you could use CacheManager for example.
I have a web application (MainApplication) where many of the pages contain a custom Web Control that looks for some content in a cache. If it can't find any data within the cache, then it goes out to a database for the content. After retrieving the content, the Control displays the content on the page.
There is a web application (CMS) in a subdirectory within the aforementioned web application. Users use this CMS to update the content pulled in by the MainApplication.
When a user updates some content using the CMS, I need the CMS to clear the relevant portion of the cache used by the MainApplication. The problem is that, as two different web applications, they can't simply interact with the same static cache object.
The ideal solution would be to somehow share an instance of a cache object between both web applications.
Failing that, what would be the best (performance-wise) way of communicating between the two web applications? Obviously, writing/reading to a database would defeat the purpose. I was thinking about a flat file?
Update
Thank you all for your help. Your wonderful answers actually gave me the right search terms to discover that this was a duplicate question (sorry!): Cache invalidation between two web applications
We had the exact same setup in a previous project i worked on, where we had one ASP.NET Web Application (with MCMS Backing), and another ASP.NET Web Application to display data.
Completely different servers (same domain though).
However, when a "editor" updated content in the CMS application, the UI was automatically refreshed.
How? Glad you asked.
We stored the content in SQL Server, and used Replication. :)
The "frontend" Web Application would read the data from the database (which was replicated by the CMS system).
Now - we don't cache this data, because in the database, we actually stored the markup (the HTML) for the control. Therefore we dynamically re-rendered the HTML.
Why is that "defeating the purpose"?
You can't get one application to "invalidate" the cache on another application.
If you're going down this path, you need to consider a distributed caching engine (e.g Velocity).
One option that comes to my mind in such scenario is using Velocity distributed cache mechanism. Do read about it and give it a try if possible http://msdn.microsoft.com/en-us/magazine/dd861287.aspx
In ASP.NET there is the notion of Cache Dependency. You can have a look here: http://www.codeproject.com/KB/web-cache/CachingDependencies.aspx or http://www.devx.com/dotnet/Article/27865/0/page/5.
There is also the Enterprise Library Caching Block available here that adds some feature to the standard stuff: http://msdn.microsoft.com/en-us/library/ff649093.aspx
Now, if you're running on .NET 4, there is a new System.Runtime.Caching namespace that you should definitely use: http://msdn.microsoft.com/en-us/library/system.runtime.caching.aspx
This article here "Caching in ASP.NET with the SqlCacheDependency Class" is quite interesting: http://msdn.microsoft.com/en-us/library/ms178604.aspx
I have a situation where information about a user is stored in the web application cache and when that information is updated in one application - I want to notify the other applications (running on the same machine) that the data should be removed from it's cache so it can be refreshed. Basically I need to keep cached data in sync across multiple asp.net applications.
I have started down the path of using a central web service to help coordinate the notifcations but it is turning out to be more complex than I think it needs to be.
Is there a way that one asp.net application can easily reach across to another on the same box to clear an item from the cache?
Is there a better way to achieve shared cached information than using the application cache?
I really want to create a way for apps to communicate in a loosely coupled way - I looked at nservice bus but the dependency on MSMQ scared me away - my client has had bad experiences with MSMQ and does not want to support an app that requires it.
Suggestions?
Michael
I agree with Hogan. Best is to use a shared database. I want to add to that that, when using SQL Server, you can use SQL Cache Dependency. This SQL Server mechanism allows notifications to applications in such a way that used caches can be invalided directly after a change is made to the data.
A shared database is probably going to cause you the least pain.
Edit
Note: ASP.NET allows you to make "cache clearing" triggers on SQL server changes. Should be a quick search in the cache examples on MSDN to find some examples. Thus when the user info stored in the cache changes in the DB the local cache copy will clear and be re-loaded from the DB.
There are commercial distributed caches available for .net other than Microsoft Velocity - NCache, Coherence, etc.
How about Velocity? It's a distributed cache that works between servers as well as between applications. It has PowerShell management and all sorts of documentation to get you going faster and be far more maintainable in the long-term.
What about COM/DCOM, using namespace System.Runtime.Remoting
I realise that this is going to be a fairly niche requirement and will almost certainly raise a few "WTF's" but here goes...
Within an ASP.NET Webforms application I need to serve static content from a local client machine in order to reduce up-front bandwidth requirements as much as possible (Security policy has disabled all Browser caching). The idea is to serve CSS, images and JavaScript files from a location on the local file system referenced by filesystem links from within the Web application (Yes, I know, WTF's galore but that's how it is). The application itself will effectively be an Intranet app that's hosted externally from a client but restricted by IP range along with standard username/password security. So it's pretty much a hybrid Internet/Intranet application but we can easily roll out packages of files to client machines. I am not suggesting that we expect nor require public clients to download packages of files. We have control to an extent over the client machines in terms of the local filesystem and so on but we cannot change the caching policy.
We're using UpdatePanel controls to perform partial page updates which obviously means that we need to Microsoft AJAX JavaScript files. Presently these are being served (as standard) by a standard resource handler within IIS/ASP.NET. Ideally I would like to be able to take these JS files and reference them statically from a client machine, and no longer serve them via an AXD.
My questions are:Is this possible?If it is possible, how do we go about doing so?
In order to attempt to pre-empt some WTF's the requirement stems from attempting to service a requirement with as little time and effort as possible whilst a more suitable solution is developed. I'm aware that we can lighten the load, we can switch to jQuery AJAX updates, we can rewrite the front-end in MVC etc. but my question is related to what we can quickly deploy with our existing application architecture.
Many thanks in advance :)
Lorna,
maybe your security team is going crazy. What is the difference between serving a dynamic HTML generated by the server and a dynamic JS generated by the server?
It does not make any sense. You should try talking them out of it.
what is the average size of pages and viewstate data. you might need to store viewstate in sqlserver rather than sending it to client browser every time.
I use the ASP.Net ScriptManager to load the scripts needed for calling WCF services via HTTP/JSON. I am optimizing the total size of my pages (including scripts) and I see that Microsoft's AJAX library is the biggest file that I have at 96KB. Is there anyway that I can get a version of this file with just the features I need loaded?
Or since I already have jquery, should I use that to call my WCF JSON service instead?
Cheers,
Jon
WCF JSON services degrade gracefully down to working as a standard webservice, so you should have no problems using jQuery to post and retrieve data from them. You may lose some of the integration bells and whistles, but as someone who has taken the path you're suggesting, I can say that I don't miss it at all.
The only problem might be if you're using advanced WCF feature like 2 way connections, or guaranteed connections.