One of my Favorite feature of ASP.NET 4.0 is that we can offload the ouputcache from in-Process memory to external storage. i.e Disk, or a big in-memory cache. then we can Cache more Data instead of being flushed out of memory when asp.net worker process get a lot pressure. this will be more helpful during the holidays season.
Coherence is one popular in-memory distributed cache cluster. I just spent 30 minutes to build one simple outputcache provider. less than 100 lines of Code. much easier than the diskcache example:)
http://weblogs.asp.net/gunnarpeipman/archive/2009/11/19/asp-net-4-0-writing-custom-output-cache-providers.aspx
Key Points,
- Keep the object in-memory, we need take care the object serialization /deserialization
- this can be done easily in .NET. there are 5+ different serializer/formatters
- I will use the BinaryFormatter which is more space -efficient
- every cache item has a expiry setting, need flush and purge it when it reaches lifetime settings.
- Coherence has the overflow setting,
- you can specify the ttl when inserting object into the cache.
Steps.
- Setup your distributed Cache Cluster and one dedicated cache.
- Reference Coherence Assembly and fill up 4 methods which are required by OutputCacheProvider
- Config asp.net web.config, point the provider to ours.
Setup your distributed Cache Cluster and one dedicated cache. here I will define one cache called outputcache to hold all the cached data.
Build the CoherencCacheOutputCacheProvider.
- Create one Class library project named CoherencCacheOutputCacheProviderLib
- reference several dlls.
- System.web.dll (where OutputCacheProdiver exists)
- System.configuration
- Coherence.dll
- Create one Class named CoherencCacheOutputCacheProvider
- Compile
- here is the source code. you may just copy and paste .
change your asp.net application to using the New cache provider.
- reference the dll we just compiled
- change the web.config
- tune you outputcache settings.
here is the web.config
testing and make sure cache works as it should be.
first, I create one simple page just pringout the current time, enable the outputcache and setup duration to 30 seconds. and very by url parameter x
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="testcache.aspx.cs" Inherits="testcache" %>
<%@ OutputCache Duration="30" VaryByParam="x" %>
Last Update :<% =System.DateTime.Now %>
When I browse http://localhost:39847/WebSite1/testcache.aspx?x=1
the runtime will create two cache items, one is the Cachevary, another one is page itself.
when try different x value, will get more cached object.
the key for the item is url+xvalue.
Let me change the cache logic to vary by browser.
<%@ OutputCache Duration="30" VaryByParam="none" VaryByHeader="user-agent" %>
then try IE/Chrome/Opera.
Since we config the cache expiry setting to 30 seconds. so let’s verify the cache item are gone once they get expired.
it is!
Conclusion:
asp.net 4.0 provider model is very convenient for extension. OutputCacheProvider comes to a citizen of the provervider model.
just like the coherence session provider for asp.net, it’s plug and play. write once , and enjoy the benefit everywhere.
