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

[Galder Zamarreno]

Manik Surtani wrote:
> 
> 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?

Absolutely :). I'll do it later today.

> 
> 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?

Defo.

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

-- 
Galder Zamarreño
Sr. Software Maintenance Engineer
JBoss, a division of Red Hat