Hello- My understanding is that the question is about the possibility of a race condition between two client requests. I would take a look at the section "Order in the Presence of Connection Loss" in the "ZooKeeper: Distributed Process Coordination" book for the best answer to this question.
Thanks, Abe On Mon, Nov 13, 2017, at 06:17, Andor Molnar wrote: > Hi baotiao, > > First, requests are acknowledged back to the client once the leader > accepted and written them in its transaction log, which guarantees that > in > case of a crash, pending transactions can be processed on restart. > Transactions IDs (zxid) are incremental and generated by the leader. > Second, Zab guarantees that if the leader broadcast T and T' in that > order, > each server must commit T before committing T'. > > With these 2 promises, I believe, that FIFO is guaranteed by Zookeeper. > > Would you please clarify that what do you mean by "set b=1 operation is > on > the way"? > > If "set b=1" is accepted by the leader, the client won't have to resend > it > on reconnect. > > Regards, > Andor > > > On Mon, Nov 13, 2017 at 5:01 AM, 陈宗志 <baot...@gmail.com> wrote: > > > I want to know in the following situation, how zookeeper promise client > > FIFO order. > > > > the client sent three operation to server, set a = 1, set b = 1, set ready > > = true. > > > > is it possible to this situation that the set a = 1 is process by the > > leader, then there is something wrong with this tcp connection, this client > > reconnect a new tcp connection to the leader, but the set b = 1 operation > > is on the way. then the client will use the new tcp connection to sent set > > ready = true operation. so the set a = 1 is operated, set b = 1 is not and > > set ready = true is operated too. > > > > the question is how zab promise client FIFO order? > > > > zab can resend all the operation that hasn't be replied from the leader. > > then in this situation, when the client reconnect to the leader, it will > > resent the operation set b = 1, set ready = true. > > > > is this the way the zab used to primise FIFO order? > > > > Thank you all > > > > -- > > --- > > Blog: http://www.chenzongzhi.info > > Twitter: https://twitter.com/baotiao <https://twitter.com/#%21/baotiao> > > Git: https://github.com/baotiao > >
