[infinispan-dev] Total Order non-transactional cache

[Pedro Ruivo]

Hi Pierre,

Thanks for the feedback.

My comments are inline.

Cheers,
Pedro

On 11/17/2014 12:22 PM, Pierre Sutra wrote:
> Hello Pedro,
>
> I read your design page with interest, and formulated a few
> remarks/questions below. Despite I do not know in details the internals,
> I Hope that they might be useful.
>
> Cheers,
> Pierre
>
> - It is unclear to me how the protocol execute reads, in particular
> regarding causality. If a reader waits for a single replica to answer,
> in case every write requires all replicas to answer, this is fine.
> However, it seems that a writer can return as soon as a single replica
> returns an acknowledgement. In such a case, it might be the case that a
> reader do not see its own modifications, if it retrieves data from a
> replica that did not apply the modifications yet.

You're right. The writer must wait for all the replies except if the 
cache is full replicated (in this case, it can wait for the self-deliver).

>
> - Do you ensure impotency of commands inside ISPN ? In my understanding,
> it is necessary when switching from a view v1 to a view v2, as commands
> delivered at the end of v1 might be already executed.

I'm lost here. can you be clear? are you talking about JGroups view or 
Infinispan cache topology?

On the latter matters and it will delivered the cache topology changes 
in total order. So, everybody receives the same order of events.

>
> - I would call your replication protocol "virtual synchrony based"
> instead, as it is relying on the virtual synchrony abstraction provided
> by JGroups.

I don't think so. If I recall correctly, virtual synchrony ensures that 
if a message is sent in view *v* then it is delivered in view *v*.

First, that cases is not necessary since we retry the commands received 
in different topologies. Second, the protocol relies on the order in 
which the operations are delivered.

>
>
> On 10. 11. 14 15:49, Pedro Ruivo wrote:
>> Hi,
>>
>> FYI, I've just created a design page:
>> https://github.com/infinispan/infinispan/wiki/Total-Order-non-Transactional-Cache
>>
>> My plan is to implement it in 7.1 release.
>>
>> Feel free to comment.
>>
>> Cheers,
>> Pedro
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