On 17 Jun 2013, at 11:52, Pedro Ruivo <pedro(a)infinispan.org> wrote:
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)
indeed this is suboptimal for
transactions that write the same key repeatedly and repeatable read. Can you please create
a JIRA for this?
#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?
This was added in the scope of
ISPN-2688 and covers the scenario in which a state transfer is in progress, the remote get
returns null as the remote value was dropped (no longer owner) and this node has become
the owner in between.
#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...
I think that, given that the local node is not owner, the
lock acquisition is redundant even for pessimistic caches.
Mind creating a test to check if dropping that lock acquisition doesn't break things?
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!
Indeed sounds like a bug, well spotted.
Can you please add a UT to confirm it and raise a JIRA?
Cheers,
--
Mircea Markus
Infinispan lead (
www.infinispan.org)