Re: Get by group?

I'm not sure about how your first request (retrieving all objects in a 
group) would be implemented... In particular, how would you suggest this 
work wrt specifying a refresh period or cron expiry when retrieving the 
group?

If ANY content in the group was deemed to be expired (determined by 
iterating the entire group), I guess the 'sensible' thing to do is to 
flush the group. Which would mean what, throwing a NeedsRefreshException 
and bundling the whole group with it? What then happens with content 
that is in multiple groups - cascading the group flushing sounds 
potentially very messy.

To tackle your second problem I think you'd be better off storing the 
group names with your cached objects. That way you can flush the desired 
group(s) manually yourself as you handle the NeedsRefreshException when 
retrieving a stale object.

Taking a step back however, I get the feeling you're trying to achieve 
something far beyond what OSCache is trying to provide you. It sounds 
like you're trying to use OSCache as an in-memory database rather than a 
caching layer. Even if group retrieval and automated group flushing was 
added, what would happen when an object was pushed out of the cache not 
because it expired but because it dropped off the end of the LRUCache? 
Events would need to be added to catch and handle that too.

If additional events were added that were fired by the caching 
algorithms upon object removal, and a method to retrieve entire groups 
was added, you could probably build the rest of the plumbing yourself. 
However I'm not sure this is a good approach. Have you considered 
caching not individual objects but an entire group's worth as a single 
cache entry?

Thoughts?
Chris


[email protected] wrote:
> All,
> 
> I am using OSCache as a caching API in a servlet based application.  The
> groups functionality holds great promise for what I need, but isn't quite
> there.  Why does OSCache not support retrieving a List of objects from the
> cache by group name?  I can group things in cache, which is great for
> expiring a number of related objects at a time, but I can't retrieve those
> related objects by the group name.  This capability is absolutely imperative
> for me.  Is anyone else doing something similar?  
> 
> The other thing I would like is for the entire group to be expired together
> if any member of the group is expired.  When an object is expired, the cache
> would have to iterate over the groups that that object is a part of and
> expire all of the other objects in the cache (expire by group name).  The
> reason that this part is important is because I would like to provide
> methods that return lists of objects in the cache (based on group name), and
> I need to be sure the list is complete.  If I put the complete list into the
> cache, but later on, one or more objects in a group are expired (perhaps
> because the size limit has been reached), this list is no longer complete
> and I need to go to the database again and retrieve the complete list.
> 
> I would love to hear if someone else is doing something similar and has
> figured out a different way of doing it.
> 
> Thanks,
> 
> Chris Black
> 
> 
> 
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