I just read through the wiki. It seems fine to me. Please feel free to add documentation to that wiki and get it reviewed by folks on the list.
Thanks mahadev On 12/9/10 1:29 PM, "Jeremy Hanna" <[email protected]> wrote: I created a link off of the main wiki and the page itself: http://wiki.apache.org/hadoop/ZooKeeper/FailureScenarios Would someone please review it? Specifically, I am curious to know about this: "if the leader is in the non-quorum side of the partition, that side of the partition will recognize that it no longer has a quorum of the ensemble. The leader will be demoted to being a regular ZooKeeper server and those nodes will no longer accept reads or writes." I just wanted to clarify - in the time for the non-quorum side to recognize it is no longer a quorum, will there ever be writes that get through? Is it guaranteed that it won't accept writes after the partition? I don't think that guarantee can exist, but wondered how to handle that. On Dec 9, 2010, at 2:04 PM, Mahadev Konar wrote: > Hi Jeremy, > Responses in line below: > > On 12/9/10 11:53 AM, "Jeremy Hanna" <[email protected]> wrote: > > I looked around on the wiki and in the user list archives and couldn't find > something definitive about certain failure scenarios. > > A partition splits the ensemble where a quorum is on one side of the partition > -- if the leader is on the quorum side of the partition, what happens to > reads/writes that go to the non-quorum side? I assume writes return errors > because it can't get to the leader. Reads? > >> The reads will also fail on all the quorum nodes until a new quorum is >> elected. > > -- if the leader is on the non-quorum side of the partition, I would assume > that the quorum side of the partition would elect a new leader for those > clients on its side of the partition. However, is there the possibility for > the leader on the non-quorum side to accept writes before it realizes that > there's no longer a quorum? Just wondering about the possibility of > corruption and then when the cluster syncs back up how the cluster would > handle that data. > >> No there isnt. The leader relinquishes its right as a leader as soon as it >> realizes a quorum isnt committing the changes it proposed. > > (I would be happy to create a wiki page for failure scenarios if one doesn't > exist that people could add to, but maybe this is just common knowledge.) > >> Please do! > > thanks > mahadev
