[infinispan-dev] DIST-SYNC, put(), a problem and a solution

[Pedro Ruivo]

On 08/06/2014 04:19 PM, Bela Ban wrote:
>
> I think this can be used for both cases; however, I think either Sanne's
> solution of using seqnos *per key* and updating in the order of seqnos
> or using Pedro's total order impl are probably better solutions.
>
> I'm not pretending these solutions are final (e.g. Sanne's solution
> needs more thought when multiple keys are involved), but we should at
> least acknowledge the issue exists, create a JIRA to prioritize it and
> then start discussing solutions.
>

I'm not sure if Sanne's suggestion will work. Imagine the follow scenario:

* a thread pool with a single thread (for simplicity)
* 3 nodes, A, B and C.
* A is the primary owner of K1 and backup owner of K2
* B is the primary owner of K2 and backup owner if K1

NodeC requests two puts concurrently to K1 and K2. Both NodeA and NodeB 
will process the request, assign a sequence number and send it to the 
backup owners. In this case, we have a deadlock again because the send 
to the backup owner is synchronous.

cause: The thread pool is exhausted because the thread is blocking 
waiting for the reply from the backup owner.

Any thoughts how can we solve this? Also, will the state transfer need 
to be adapted to the new behaviour?

Pedro