[infinispan-dev] AtomicMap and mutable objects

[Manik Surtani]

Hi Emmanuel.

With RepeatableRead, tx2 won't see the update till tx1 commits because the update (map.put()) is held in a change list until the tx is committed, before it is applied to the underlying AtomicMap.  (Remember, what you get is a proxy).

Ah, I see your question though; assuming the reference to the date is the same.  Hmm, in this case you may well see the change before tx1 commits, we don't explicitly clone or copy mutable objects.  We assume objects in an atomic map are immutable.  I suppose though we could add the ability to defensively copy mutable objects, but we'd need a way of knowing which are immutable, etc.  Also, this would be more expensive, depending on the size of the atomic map.

Cheers
Manik

PS: This is probably a discussion for infinispan-dev.



On 3 Dec 2010, at 09:47, Emmanuel Bernard wrote:

> Hey Manik and all,
> 
> We had a talk at Devoxx on AtomicMap and tx isolation but its back to fuzzyness to me. can you help me reclarify.
> 
> Here is the scenario.
> 
> In Tx1
> Map map = (AtomicMap) cache.get( key1 );
> Date updateDate = map.get("date");
> updateDate.setTime( System.currentTimeMillis() );
> #cp 1
> map.put("date", updateDate);
> End of Tx1
> 
> In Tx2
> Map map = (AtomicMap) cache.get( key1 );
> Date updateDate = map.get("date");
> #cp2
> display(updateDate);
> End of Tx2
> 
> Provided Date is mutable and assuming Tx1 and Tx2 run in the same node. Could it be that Tx2 display the new value of updateDate before Tx1 is committed. Or are you guys copying on read mutable objects?
> 
> Emmanuel

--
Manik Surtani
manik at jboss.org
Lead, Infinispan
Lead, JBoss Cache
http://www.infinispan.org
http://www.jbosscache.org