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Comment by stmw | Hacker News Reader

Both the Raft algorithm and its explanation are excellent, including this little animated demo that Diego Ongaro (who is also a great guy) made to help explain his invention. While Paxos was first and still popular, I am not sure I would count against any senior engineer unable to explain it to others. With Raft, one ought to be able to do it. Great to see this on HN.

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I just want to clarify that, strictly speaking, Paxos is simpler than Raft. Like Paxos is Raft plus "delete the part where the new leader has to be fully caught-up" (which causes an extra weirdness in Raft when the leader got majority adoption of a new log entry but failed to commit it due to network partition) plus "delete the part where the leader election elects the leader, you can do that and it's called multi-paxos, but if your use case isn't big enough you can instead just elect the next log entry, but it doesn't have to have the form "this is our new leader, all hail" (but in practice this is what everyone does).

I think the Raft paper is more approachable for newcomers, but if you are finding Paxos hard to explain and Raft easy to explain, just use the Raft lingo to explain Paxos.

Worth noting, not quite "everyone" does this. Cassandra uses "leaderless" (single decree) paxos, which has some advantages and some disadvantages (for instance, 1RT WAN reads from any region).

I agree with you that Paxos is simpler than Raft. The problem with Paxos IMO is that Lamport's original paper is impenetrable; lots of later writing is easier to understand, including those that describe more complex protocols. The intuitions are actually pretty straightforward, and transfer to all of the extensions to Paxos (which are not as straightforwardly compatible with Raft).

Raft may have helped more people get comfortable with distributed consensus, and sped its adoption, but being a sort of dangling branch of the tech tree I wonder if this may have stalled progress beyond it.

Interesting way to think about, I am not sure I quite agree, but good points and surrounding discussion for sure..

It is darkly amusing to me that Paxos is still cited by people as a "good algorithm" to choose and understandable - including the cutesy island metaphor from the paper to appear approachable - and the Raft paper opens with a paragraph more or less going "ok we had a bunch of people try to understand Paxos and none of them could figure it out". Anytime I see someone recommend Paxos I silently am judging if they've actually ever read the paper or just parroting advice from when it was the only game in town.

Do you ever bother to ask whether they are recommending it for a use case other than a replicated log?

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