Hi all,
I'm studying Paxos in Ceph because I need to add one new
PaxosService.
In Ceph, the Paxos is based on a single-proposer & multi-acceptors.
So, the quorum need choose the single-proposer(leader) first.
It seems that there're two ways to choose one monitor as leader:
I'm curious that why their pre-conditions are different.
------------
This doesn't block me to continue my development work. I just want to
know why.
Does anyone know that reason?
I. Normal way:
Elector::handle_ack
|--> logic.receive_ack(peer_rank, m->epoch);
|--> declare_victory();
// Note: pre-condition is below
-------------
electing_me && (acked_me.size() == elector->paxos_size())
II. Another way if timeout event happen:
Elector::_start() or Elector::_defer_to
|--> reset_timer();
|--> expire_event = mon->timer.add_event_after(
g_conf()->mon_election_timeout + plus,
new C_MonContext{
mon, [this](int) {
logic.end_election_period();
}
});
When timeout happens:
ElectionLogic::end_election_period()
|--> declare_victory();
// Note: pre-condition is below
-------------
electing_me && acked_me.size() > (elector->paxos_size() / 2)
B.R.
Changcheng
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