[infinispan-dev] rehashing hazard

[Mircea Markus]

On 25 Oct 2010, at 11:52, Manik Surtani wrote:

> 
> On 22 Oct 2010, at 17:01, Mircea Markus wrote:
> 
>> 
>> On 22 Oct 2010, at 15:17, Vladimir Blagojevic wrote:
>>> 
>>>>> 
>>>>> The operations that need to be sequential are state transfer and tx log transfer. 
>>>>> State is being *pulled* by C (thread running on C) and tx log is *pushed* by A (thread running on A). Two threads running in different VMs. 
>>>> 
>>>> Ok, this would be the issue then - this must have changed when Vladimir inverted the leave task to be a pull for the main state.  They both used to be pushes and sequential.
>>>> 
>>>> Perhaps the sequentiality can be re-established by a lock on the receiver?
>>> 
>>> Interested. What if C thread announce that it pulled state and upon reception of this message A drains the logs?
>> 
>> Is there any work that can be done in parallel? State transfer and log draining need to happen in sequence.
>> If not what's the point of using two threads?
> 
> They are not just 2 threads - they are on 2 separate nodes.  State tfr is initiated by the receiver; tx log training by the sender.  
Why can't the sender initiate state transfer and then drain tx log? I.e. a thread on the sender write state and then write tx log. No sync needed then.
> Hence the different threads.  Modifying the protocol to allow for a state tfr ack message, as Vlad suggested, would work fine.
> 
>> One thread approach would be more maintainable and simple. I emphasise _maintainable_ because I've just debugged logs of state transfer and it's not the nicest thing to do.
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> --
> Manik Surtani
> manik at jboss.org
> Lead, Infinispan
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