I've changed a server from Observer to Leader under a similar scenario (data migration form old DC to new DC) without any problem. Just stop all servers, change the configuration and start up all servers. Everything should work fine. /César.
On Tue, Jul 10, 2012 at 4:40 PM, Raj N <[email protected]> wrote: > I am purely talking about a DR scenario. As in we can safely assume that > the primary DC is no longer available. Also before the DR, the clients were > connecting to the ZK ensemble in primary and after the DR they will connect > to the ZK ensemble in secondary DC. You wont have a split brain problem. > The only problem I see is potential loss of some data. The question really > was if there are any gotchas in reconfiguring a Zookeeper node which was a > observer to now be a leader/follower. > > Thanks > -Raj > > On Tue, Jul 10, 2012 at 6:31 AM, David Nickerson < > [email protected]> wrote: > > > Hi Raj, > > > > I've been considering this same solution for my project. Let's say that > the > > secondary DC automatically makes its own quorum when it can no-longer see > > the primary. Then you have a case where a network partition can result in > > your quorum splitting into two autonomously running quorums. (ZooKeeper's > > majority rule exists to prevent this situation.) Just make sure that you > > have some additional logic that invalidates the primary once it can > > no-longer be found. > > > > On Tue, Jul 10, 2012 at 3:39 AM, César Álvarez Núñez < > > [email protected]> wrote: > > > > > Yes you can. Just edit the zoo.cfg from the backup DC, comment the > lines > > > relative to the nodes in the primary DC and the observer peer type. > > > > > > In this way you can start a new ZK ensemble with just the 3 servers on > > > backup DC. > > > > > > But be aware that due to latency issues the backup DC could not have > the > > > latest changes from the active DC. > > > > > > You will also need to update each client "connection string" to use > only > > > the servers from the backup DC. > > > > > > /Sent from my GP0. > > > El 09/07/2012 23:16, "Raj N" <[email protected]> escribió: > > > > > > > Let's say you have 2 DCs, primary and secondary. The primary DC has > a 3 > > > > node zookeeper quorum. And the secondary DC has 3 nodes that are > > > observers. > > > > Is it possible in a DR scenario(primary down) to make the 3 observer > > > nodes > > > > the new quorum? > > > > > > > > Thanks > > > > -Raj > > > > > > > > > >
