Leader elections never start after a leader is lost if there is a member with election_mode = 'off' in the replica set #12018
Description
Bug description
Nodes with election_mode = 'off' do not have a leader tracking timer, but continue broadcasting leader_is_seen = true.
This prevents leader reelection in case of a mixed setup, where some nodes have election_mode = 'off' and others have election_mode = 'candidate', since the candidates won't start the elections until at least one node reports that it sees the leader, and the election_mode = 'off' node will forever report the leader as seen.
Reproducer: start 4 tarantool instances in separate consoles, configure 3 of them as candidates, and one with election_mode = 'off', also set replication_synchro_quorum = 2. Then kill the elected leader. No new leader will emerge:
--
-- Instance 1.
--
-- Step 1.
box.cfg{
listen = 3301,
replication = {
3301,
3302,
3303,
3304,
},
election_mode = 'candidate',
replication_synchro_quorum = 2,
}
-- Step 5. Execute it on the currently active leader. Might be any of the instances 1,2,3:
box.schema.user.grant('guest', 'replication')
-- Step 6. Also on the current leader.
box.info.election -- state: leader
os.exit()
--
-- Instance 2.
--
-- Step 2.
box.cfg{
listen = 3302,
replication = {
3301,
3302,
3303,
3304,
},
election_mode = 'candidate',
replication_synchro_quorum = 2,
}
-- Step 7.
box.info.election -- state: follower--
-- Instance 3.
--
-- Step 3.
box.cfg{
listen = 3303,
replication = {
3301,
3302,
3303,
3304,
},
election_mode = 'candidate',
replication_synchro_quorum = 2,
}
-- Step 8.
box.info.election -- state: follower--
-- Instance 4.
--
-- Step 4.
box.cfg{
listen = 3304,
replication = {
3301,
3302,
3303,
3304,
},
election_mode = 'off',
replication_synchro_quorum = 2,
}