5 ms·
The split-brain scenarios you mention cannot occur, since all the proposals have to go through the leader before they are agreed to by any processes. Moreover,
by oggy 10y ago
The split-brain scenarios you mention cannot occur, since all the proposals have to go through the leader before they are agreed to by any processes.
Moreover, the leaders are lease-based in the author's proposal, so I believe that what he describes correctly solves consensus. However, his proposal doesn't really give
much of a resilience improvement over the original Paxos, since the system, in the worst case, tolerates only 2 failures (leader + one more process), same as a 5-process Paxos. Nevertheless, an interesting idea, one that I don't think I've seen elsewhere.
- maccilia 10y agoSo I'm pretty a similar problem could exist. If to accept a proposal we only need 3 nodes, not a majority, and we manipulate network latency in arbitrarily bad ways, a similar split brain could occur. Basically, you could commit the same transaction twice under different proposal numbers.
- oggy 10y agoConsensus is not about transactions, it's about agreeing on a value (a single value, strictly speaking, unlike atomic broadcast, which is about agreeing on a sequence of values, although people often identify the two). But anyway, your argument is not in any way concrete - try to come up with a counterexample. Having thought about it more, I am confident that the author's system is correct (in the sense that it always preserves agreement).