Maybe I am not understanding. Server 1 starts up as a single server raft cluster taking writes. (N/2 +1) is 1 so it has majority and can commit writes.
Server 2 starts up as a single server raft cluster taking writes. (N/2 +1) is 1 so it has majority and can commit writes. Both servers are unaware of each other. Then we merge the two servers into a single raft cluster. What happens in this scenario? On Thu., Jul. 14, 2022, 1:30 p.m. Tsz Wo Sze, <[email protected]> wrote: > When the number of nodes n is even, a majority requires (n/2 + 1) nodes. > When there are two nodes, it requires two nodes in order to have a majority. > > Tsz-Wo > > On Thu, Jul 14, 2022 at 10:07 AM Asad Awadia <[email protected]> wrote: > >> So that's the thing. Both have a majority. Since there are two 'clusters' >> of 1 node each. There are only 2 nodes. ( i know should be odd) >> >> So both sides think they have majority right? What then? >> >> Regards, >> Asad >> >> >> On Thu., Jul. 14, 2022, 11:49 a.m. Tsz Wo Sze, <[email protected]> >> wrote: >> >>> Hi Asad, >>> >>> Raft uses majority for committing transactions. When two nodes are not >>> aware of each other are both taking writes, at most one of them can get a >>> majority. The one(s) without majority cannot commit any transactions. >>> When these two nodes are merged, if one of them had the majority >>> previously, the one without majority won't be voted as the leader so that >>> its (non-committed) transactions will be dropped. >>> >>> For the details, please see the Raft paper >>> https://raft.github.io/raft.pdf . It should be discussed in Section >>> 5.4 Safety. >>> >>> Tsz-Wo >>> >>> >>> >>> On Thu, Jul 14, 2022 at 6:57 AM Asad Awadia <[email protected]> >>> wrote: >>> >>>> Hello, >>>> >>>> How does ratis handle split brain? (Using the term counter?) >>>> >>>> That is two nodes are not aware of each other are both taking writes >>>> and now are merged into one cluster with one leader. >>>> >>>> How are the writes reconciled? Whose work is overwritten? Or is the >>>> cluster now in a bad state in need of manual intervention? >>>> >>>> Regards, >>>> Asad >>>> >>>
