Correct. I forgot about the readonly mode, thanks. If readonly mode is enabled, you cloud have stale reads definitely.
Andor On Thu, May 10, 2018 at 3:24 PM, s n <[email protected]> wrote: > *ReadOnlyMode Servers* > > ReadOnlyMode allows clients sessions which requested ROM support to connect > to the server even when the server might be partitioned from the quorum. In > this mode ROM clients can still read values from the ZK service, but will > be unable to write values and see changes from other clients > > Wouldn't this cause stale reads in case of network partition ? > > > On Thu, May 10, 2018 at 2:26 PM, Andor Molnar <[email protected]> wrote: > > > You cannot read from ZooKeeper if there's no quorum, because it rejects > > client connections. > > But when you can, the request doesn't go to the leader, it served > directly > > from the server that client is connected to. > > > > As a consequence, you cannot read stale data from ZooKeeper. > > > > Andor > > > > > > > > On Thu, May 10, 2018 at 1:36 PM, David Brower <[email protected]> > > wrote: > > > > > Without quorum, the client has no idea how current the read data may > be. > > > It might be from a replica that is hours/days/weeks out of data. > > > Sometimes this won't matter, sometimes it will be a critical failing. > > > > > > -dB > > > > > > > > > > > > On 5/9/2018 6:40 PM, Prasanth Mathialagan wrote: > > > > > >> For reads, is Quorum necessary? Reads are served from local the local > > >> replica, right? > > >> > > >> On Wed, May 9, 2018 at 8:29 AM, Jordan Zimmerman < > > >> [email protected] > > >> > > >>> wrote: > > >>> A quorum means (n/2)+1 - In a 3 node cluster that is 2. So, if 2 > > servers > > >>> are up you can achieve quorum. > > >>> > > >>> we need odd > > >>>> numbers in order to form a quorum > > >>>> > > >>> The "odd" in this formula refers to the number of configured servers > > not > > >>> how many are running at a given time. That's the reasoning for quorum > > in > > >>> the first place. Quorum I/O ensures that a majority of nodes is > > >>> referenced > > >>> for reads or writes (in ZooKeeper writes are what matter for quorum). > > >>> > > >>> -Jordan > > >>> > > >>> On May 9, 2018, at 10:26 AM, Kaushal Shriyan < > [email protected] > > > > > >>>> > > >>> wrote: > > >>> > > >>>> Hi, > > >>>> > > >>>> In a ensemble of 3 nodes with 1 leader and 2 followers, if the > leader > > >>>> > > >>> goes > > >>> > > >>>> down then two servers can elect a leader among themselves. But we > need > > >>>> > > >>> odd > > >>> > > >>>> numbers in order to form a quorum. I am confused. Please correct me > > if i > > >>>> > > >>> am > > >>> > > >>>> understanding it wrong. > > >>>> > > >>>> Any help will be highly appreciable > > >>>> > > >>>> Best Regards, > > >>>> > > >>>> Kaushal > > >>>> > > >>> > > >>> > > > > > >
