NHibernate Second Level Cache with database change notification on desktop App

Question

I am developing a WPF application using NHibernate to communicate with a PostgreSQL Database. The only caching provider that works on a desktop app is Bamboo Prevalence (correct me if I am wrong). Given that every computer running my application will have different Session Factory, my application retrieves stale data from the cache.

My question is, how can I tell NHibernate/Prevalence to look at the timestamp of when the data was last updated, and if the cache is stale, refresh it?

Answer 1

Well, I found out that there is no way the Second Level cache can know if the database was changed outside Nhibernate/Cache, so what I did was creating a new column 'Timestamp' on all my tables.

On my queries, I first select the timestamp of the db using Session.Cachemode(CacheMode.Ignore) to get the timestamp of the db and I compare with the result from the cache. In the case the timestamps differ, I invalidate the cache for that query and run it again.

About the SysCache, even knowing it 'can work' on a WPF desktop app, I was not keen to use System.Web.Cache as my application would need the the complete .Net Framework instead of the Client Profile. I did a search and for my happiness someone wrote a Nhiberate cache proviver that implements (System.Runtime.Caching), witch is not a ASP.Net component. If anyone is interested you can find the source at: https://github.com/Leftyx/nhcontrib/tree/master/src/NHibernate.Caches/MemoryCache

Answer 2

Well that is a property that you could set at the cache level and expire items according to your applications needs and then have the cache. Ncache is a possible L2 cache provider for NHibernate. NCache ensures that its cache is consistent across multiple servers and all cache updates are synchronized correctly so no data integrity issues arise. To learn more please visit:

http://www.alachisoft.com/ncache/nhibernate-l2cache-index.html