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

[Bela Ban]

On 29/07/14 20:06, Sanne Grinovero wrote:
> This is a nasty problem and I also feel passionately we need to get
> rid of it ASAP.

+1

> I did have the same problems many times, and we discussed this also in
> Farnborough; AFAIR Dan and Pedro had some excellent ideas to fix this.
>
> You don't need TO, and you don't need to lock at all as long as you
> guarantee the backup owners are getting the number with some
> monotonicity sequence attached to it,
> all that backup owners need to do is ignore incoming commands which
> are outdated.

Right. And we need to handle the scenario where we get updates from 
multiple members, e.g. P40,P41,Q6,Q7 in the case where the primary owner 
changed from P to Q (or from Q to P ?)

> Another aspect is that the "user thread" on the primary owner needs to
> wait (at least until we improve further) and only proceed after ACK
> from backup nodes, but this is better modelled through a state
> machine. (Also discussed in Farnborough).
>
> It's also conceptually linked to:
>   - https://issues.jboss.org/browse/ISPN-1599
> As you need to separate the locks of entries from the effective user
> facing lock, at least to implement transactions on top of this model.
>
> I expect this to improve performance in a very significant way, but
> it's getting embarrassing that it's still not done; at the next face
> to face meeting we should also reserve some time for retrospective
> sessions.

Yes - there's a link to the agenda of the 2015 team meeting, please feel 
free to update the agenda. I'll send out an email re dates and location 
shortly.


[1] https://mojo.redhat.com/docs/DOC-977279

-- 
Bela Ban, JGroups lead (http://www.jgroups.org)