[infinispan-dev] Doubts about TxDistributionInterceptor and possible break in transaction isolation

[Pedro Ruivo]

Hi guys,

I've been looking at TxDistributionInterceptor and I have a couple of 
questions (assuming REPEATABLE_READ isolation level):

#1. why are we doing a remote get each time we write on a key? (huge 
perform impact if the key was previously read)

#2. why are we doing a dataContainer.get() if the remote get returns a 
null value? Shouldn't the interactions with data container be performed 
only in the (Versioned)EntryWrappingInterceptor?

#3. (I didn't verify this) why are we acquire the lock is the remote get 
is performed for a write? This looks correct for pessimistic locking but 
not for optimistic...

After this analysis, it is possible to break the isolation between 
transaction if I do a get on the key that does not exist:

tm.begin()
cache.get(k) //returns null
//in the meanwhile a transaction writes on k and commits
cache.get(k) //return the new value. IMO, this is not valid for 
REPEATABLE_READ isolation level!

wdyt?

Thanks.

Cheers,
Pedro Ruivo