[jboss-user] [JBossCache] - TreeCache data integrity across cluster

[magicmac]

Hey,

These are my first steps with JBossCache, but it seems like I already face some basic problem

Simple example:
2-node cluster, each with instance of treeCache. Out of AS.
REPL_SYNC, locking PESSIMISTIC, state is replicated on startup.

run the following algorithm on to machines concurrently:

Machine A:

for i=0..100 
     counter = tree.get(fqn,counter_key,counter_value);
     counter++;
     tree.set(fqn,counter_key);

Machine B:
    exactly the same code

The result: of course counter is <<200 since we lack synchronization of given get-put blocks. 
As I already found out there is no cluster-wide lock. The locks I can explicitly acquire on node are not broadcasted.

It seems that I need transactions for that.

Machine A:
for i=0..100 
     beginDummyTransaction
     counter = tree.get(fqn,counter_key,counter_value);
     counter++;
     tree.put(fqn,counter_key);
     commitDummyTransaction

Machine B: same as A.

Unfortunatelly with such approach I get TimeoutExceptions as B for some reason cant aquire write-lock (or A). 
The commit is a 2PC and from logs it really seems to work sync. The lock-aquiring-problem occurs when the other transaction tries to commit.

Is there any way of providing 100% integity of data when heavy updates occur in multiple cluster nodes? In my particular case, I need to buffer the stats of user buisness-logic operations of very-heavy accessed web portal. Such updates occur up to 100/sec per machine. Since there is no explicit cluster-wide locking how can I achieve it? Is there a way of aquiring write-lock at the begining of transaction (on read) and force other readers to wait till this lock is realesed on commit ? Or something like that/simulation of critical section.

I may not express myself clearly here so if you need any more info let me know.

Thanks for any light
M.


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