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

[Galder Zamarreno]

FYI: http://jira.jboss.com/jira/browse/JBCACHE-1357

Galder Zamarreno wrote:
> 
> 
> 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