Cache Managers in Enterprise Library caching Application block

caching

I have been using asp web cache in all my prior application developments. I am looking into Ent. Lib caching application block which seems pretty interesting.

However, I have need some clarifications on how the cache managers work?

1- What is the purpose of having multiple cache managers, is it to partition cahing items ? I am used to have only a single cache manager (similar to ent. lib. default cache manager)?

2- Does each cache manager maps to an individual hash table ? or they are all going to be stored in one hash table?

3- If I only use the Null storage option (no backing store) does it make a difference if I use multiple cache managers?

Thanks,

Robert B.

Best Answer

Multiple cache managers allow you to specify different policies for each. These include:

the maximum number of items you allow in the cache
how often you'd like to poll for expired items

Usually, you'd want these to be configurable based on the items you store in the cache. If you have volatile items that you store for just an hour, you'd like to poll for expired items every ten minutes. If your items can stay in the cache for a week, polling every ten minutes makes little sense and is a waste of resources.

Related Solutions

System.Web.Caching vs. Enterprise Library Caching Block

These are the items that I consider for the topic of Caching:

MemCached Win32 Velocity .net Cache Enterprise Library Caching Application Block

MemCached Win32: Up until recently I have used MemCached Win32. This is a akin to a web farm (many servers serving the same content for high availability) but it is a cache farm. This means that you can install it locally on your web server initially if you don't have the resources to go bigger. Then as you go down the road you can scale horizontally (more servers) or vertically (more hardware). This is a product that was ported from the original MemCached to work on Windows. This product has been used extensively in very high traffic sites. http://lineofthought.com/tools/memcached

Velocity: This is Microsofts answer to products such as MemCached. MemCached has been out for quite some time, Velocity is in CTP mode. I must say that from what I have read so far this product will certainly turn my head once it is out. But I can't bring myself to run big production projects on a CTP product with zero track record. I have started playing with it though as once it gains momentum MemCached won't even compare for those locked in the windows world! http://blogs.msdn.com/velocity/

.NET Cache: There is no reason to discount the standard .NET Cache. It is built in and ready to use for free and with no (major) set up required. It offers flexibility by way of offering mechanisms for storing items in local memory, a SINGLE state server, or a centralized database. Where Velocity steps in is when you need more than a single state server (cache in memory) and don't want to use a slow database for holding your cache.

Enterprise Application Block: I stay away from all of the Enterprise Application Blocks. They are heavy frameworks that give more than I generally require! As long as you remember to wrap everything that touches code that is not your own and follow simple rules for coding, stick to any of the other methods over this one! (just my opinion of course - MySpace leverages as much as they can out of Enterprise Application Blocks!)

You don't have to choose up front! I generally create a cache wrapper that I communicate with in my code for methods such as Get, Set, Exists, Remove, ListKeys, etc. This then points to an underlying level of cache abstraction that can point to MemCached, Velocity, or .NET cache. I use StructureMap (or choose another IoC container) to inject which form of cache I want to use for a given environment. In my local dev box I might use .NET cache in the session. In production I generally use MemCached Win 32. But regardless of how it is set up you can easily swap things around to try each system out to see what works best for you. You just need to make sure that you application knows as little as possible about how things are cached! Once this layer of abstraction is in place you can then do things such as run a compression algorithm (gzip) for all the data that is going in and out of cache which would allow you to store 10 times the amount of data in cache. - transparently.

I cover .NET Cache, MemCached Win32, StructureMap, and the appropriate abstractions in my book if you are interested!

ASP.NET 3.5 Social Networking (http://www.amazon.com/ASP-NET-3-5-Social-Networking-Enterprise-ready/dp/1847194788/ref=sr_1_1?ie=UTF8&s=books&qid=1225408005&sr=8-1 ) Andrew Siemer www.andrewsiemer.com blog.andrewsiemer.com www.socialnetworkingin.net

Update Changed the link that lists sites using memcached. Thank you David for noticing that it was broken!

Asp.net-mvc – How to cache data in a MVC application

Here's a nice and simple cache helper class/service I use:

using System.Runtime.Caching;  

public class InMemoryCache: ICacheService
{
    public T GetOrSet<T>(string cacheKey, Func<T> getItemCallback) where T : class
    {
        T item = MemoryCache.Default.Get(cacheKey) as T;
        if (item == null)
        {
            item = getItemCallback();
            MemoryCache.Default.Add(cacheKey, item, DateTime.Now.AddMinutes(10));
        }
        return item;
    }
}

interface ICacheService
{
    T GetOrSet<T>(string cacheKey, Func<T> getItemCallback) where T : class;
}

Usage:

cacheProvider.GetOrSet("cache key", (delegate method if cache is empty));

Cache provider will check if there's anything by the name of "cache id" in the cache, and if there's not, it will call a delegate method to fetch data and store it in cache.

Example:

var products=cacheService.GetOrSet("catalog.products", ()=>productRepository.GetAll())