wojiaodoubao commented on PR #943:
URL: https://github.com/apache/ratis/pull/943#issuecomment-1774281969
> Change from {n0} to {n0, n1}.
> This case should work well. How could it be bad?
Hi @szetszwo , sorry for my late response. I made a test to simulate this
case. Please have a look at TestMembership#testAddOneToOne. The procedure is as
below.
1. Originally we have a cluster with 1 node n0.
2. Start n1 with empty conf.
3. Call setConfiguration to n0. After n1 catches up, n0 changes to
C_old_and_C_new.
4. A network partition happens. n1 doesn't get C_old_and_C_new.
5. n0 finds no majority because n1 doesn't answer. n0 quits and restarts
election.
6. Network partition recovers.
7. n1 never votes to n0, so we won't have leader anymore.
I think the reason is: all new peers' conf are empty while the peers in
C_old has became transitional conf. Peer with transitional conf needs votes
from both C_old majority and C_new majority. But 'We can't find any majority
without new peers in C_new'. That's why we won' get new leader.
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