[jbosscache-dev] Storing k, v at root node of marshaled region and cache loaders.

[Manik Surtani]

On 29 May 2008, at 14:09, Galder Zamarreno wrote:

> Hi all,
>
> Yesterday while looking at a support case, I discovered an awkward  
> behavior when it came to root region based marshalling nodes and  
> cache loaders.
>
> Let's say you have a cache configured with a cache loader and have a  
> region marshaled called starting at /me. I have created an MBean so  
> that I can register/unregister classloader and activate/deactivate  
> the region upon deployment/undeployment of the classes I wanna put  
> under /me.
>
> Now, let's say that I put a k,v in /me which will get stored in the  
> cache loader. If I know touch the deployment archive to force a  
> redeployment and check the contents of the cache, they're empty. If  
> I try to get the k I put under /me, it'll return nothing. Why?
>
> Simple: The cache instance is configured to preload from root (/)  
> but when the region is activated, /me node is created. When the  
> preloading phase comes, a check is made to see whether the node  
> needs to be loaded:
>
>   private boolean mustLoad(DataNode n, Object key)
>   {
>      if (log.isTraceEnabled())
>      {
>         log.trace("mustLoad called with key=" + key + " and  
> datanode=" + n);
>      }
>      return n == null ||
>              (n.containsKey(TreeCache.UNINITIALIZED) && (key == null  
> || !n.containsKey(key)));
>   }
>
> The problem is that nothing will be preloaded for at least the /me  
> node, because the node is not null, and it's not  
> TreeCache.UNINITIALIZED. Any child nodes under the region node do  
> not have issues like this.
>
> This is likely a bug: maybe when the region is activated, the node  
> should probably be created as TreeCache.UNINITIALIZED? I think this  
> would work).
>
> It's true that you could say that putting data at the root node of  
> the region is not a good idea regardless, but I think deep down this  
> is a bug.

I agree this is a bug.  Could you raise a JIRA for this?

Also agree with your solution, that when a region is activated and if  
a node needs to be created, it should be uninitialized.

> Thoughts?
>
> p.s. This is at least present in 1.4.x, need to check trunk.  
> However, wanted to gather some thoughts before I continue debugging/ 
> fixing it.

If you create a unit test, could you add it to trunk as well?

Thanks
--
Manik Surtani
Lead, JBoss Cache
manik at jboss.org