Thank you lot Ibrahim
On Wed, Aug 26, 2015 at 12:15 PM, Sylvain Lebresne <sylv...@datastax.com> wrote: > Yes > > On Wed, Aug 26, 2015 at 1:05 PM, ibrahim El-sanosi < > ibrahimsaba...@gmail.com> wrote: > >> OKKKKKKKKK. I see what the purpose of acknowledgment round here. So >> acknowledgment is optional here, depend on CL setting as we normally do in >> Cassandra. >> So we can say that acknowledgment is not really related to Paxos phase, >> it depends on CL in Cassandra? >> >> Ibrahim >> >> On Wed, Aug 26, 2015 at 11:50 AM, Sylvain Lebresne <sylv...@datastax.com> >> wrote: >> >>> On Wed, Aug 26, 2015 at 12:19 PM, ibrahim El-sanosi < >>> ibrahimsaba...@gmail.com> wrote: >>> >>>> Yes, Sylvain, your answer makes more sense. The phase is in Paxos >>>> protocol sometimes called learning or decide phase, BUT this phase does not >>>> have acknowledgment round, just learning or decide message from the >>>> proposer to learners. So why we need acknowledgment round with commit phase >>>> in lightweight transactions? >>>> >>> >>> It's not _needed_ as far as Paxos is concerned. But it's useful in the >>> context of Cassandra. The commit phase is about actually persisting to >>> replica the update decided by the Paxos algorithm and thus making that >>> update visible to non paxos reads. Being able to apply normal consistencies >>> to this phase is thus useful, since it allows user to get visibility >>> guarantees even for non-paxos reads if they so wish, and that's exactly >>> what we do and why we optionally wait on acknowledgments (and I say >>> optionally because how many acks we wait on depends on the user provided >>> consistency level and if that's CL.ANY then the whole Paxos operation >>> actually return without waiting on any of those acks). >>> >>> >>> >> >
