sync() guarantees that it will synchronize the data between the zk servers at 't' th time.
Say we have two clients and both are working on the same key path: First client C1, is updating the value of x at 't1', 't2' and 't3' as follows. at t1 time, value of x = 4 at t2 time, update value of x = 5 at t3 time, update value of x = 6 Second client C2, which is doing sync() at 't2' time and invoke a read() req at 't3' time. (Ignoring the race condition between the updation of C1 and sync of C2, here assume C1 update has happened first). Now C2 will see value of x=5 from any of the ZK servers(Leader/Followers), but C2 is not guranteed to see value of x=6, as updation happened after sync() api call. -Rakesh ________________________________________ From: Ted Dunning [[email protected]] Sent: Saturday, March 02, 2013 7:33 AM To: [email protected] Subject: Re: Consistency in zookeeper Yes. Sync doesn't guarantee up to date. It guarantees an ordering. It guarantees that if event A involves a ZK update and if you can guarantee that A occurs before sync, then any read on a client C that is done after a sync on C will see a successor state of A. On Fri, Mar 1, 2013 at 2:01 PM, Jordan Zimmerman <[email protected] > wrote: > Even if you do the sync, another client can make a change before you do > the subsequent read. > > -JZ > > On Mar 1, 2013, at 1:50 PM, Martin Kou <[email protected]> wrote: > > > Yasin, > > > > If the two clients are connected to two different ZooKeeper servers in > the > > cluster, then, yes. > > > > Generally, if you're worried that there may be another client working on > > the same key path, then you should sync() before reading. > > > > Best Regards, > > Martin Kou > > > > On Fri, Mar 1, 2013 at 1:38 PM, Yasin <[email protected]> wrote: > > > >> So, if the read request is made by some other client, it will not get > the > >> updated value without sync, right? > >> > >> > >> > >> -- > >> View this message in context: > >> > http://zookeeper-user.578899.n2.nabble.com/Consistency-in-zookeeper-tp7578531p7578542.html > >> Sent from the zookeeper-user mailing list archive at Nabble.com. > >> > >
