[infinispan-dev] FineGrainedAtomicMap preview

[Vladimir Blagojevic]

> Mircea, I need your help regarding concurrent tx and
> FineGrainedAtomicMap. Have a look at
> FineGrainedAtomicMapAPITest#testConcurrentTx(the above link) as it is
> failing if I do *not* run two threads sequentially, i.e. there is a
> sleep of 2 sec to prevent concurrent tx running. Any ideas why is this
> happening? The test failed in the old locking architecture as well. In
> the old architecture, an entry was not wrapped with MVCCEntry because we
> do not look up (and lock) AtomicHashMap but we issues
> "synthetic/composite" lock requests for keys in that AtomicHashMap. If
> we look up and lock key for AtomicHashMap the the whole point of
> FineGrainedMap is lost as we would lock entire map. I noticed that
> AtomicHashMap was being wrapped with ImmortalEntry. Maybe this is why
> changes are not seen with concurrent tx, but how is it that the changes
> are seen if tx are not run concurrently? If you could demystify this for
> me I'd be grateful.
>
Mircea and others,

To answer my own question. The non-visibility of transactional changes 
was not related to Infinispan tx plumbing but a simple fact that 
AtomicHashMap class uses non-thread safe FastCopyHashMap delegate to 
store actual key/value pairs. When I changed FastCopyHashMap to 
ConcurrentHashMap my concurrent tx test started to pass.


Cheers,
Vladimir