71–80 of 91 posts
Off topic - folks in the know, besides Paxos/Raft what are some of the other most complex algorithm in computer sciences that are widely used or are a bedrock?
DLT technology discussions are entirely incomplete without consideration of Hedera Hashgraph [0], an aBFT, leaderless, fair and fast DLT using a gossip-about-gossip consensus mechanism. It's absolutely a more robust and scalable technology than Paxos or any other DLT for that matter. I'd love to know what the HN crowd thinks about Hedera as the trust layer of the internet but.... nobody around here seems to have any.…
I am in the minority who thinks Raft is overrated. I tried teaching Raft one year instead of Paxos but ended up switching back. While it was much easier to understand how to implement Raft, I think my students gained deeper insight when focusing on single-decision Paxos. There is a lightbulb moment when they first understand that consensus is a property of the system that happens first (and they can point at the mome…
Is there any paper/handouts/video that explains Paxos in depth, especially its implementations and intuitions? Paxos Made Simple gave intuitive explanations, but I feel it still misses a lot of intricate details if I were to build Praxos for production use.
I suggest https://github.com/emichael/dslabs.
It will take 100-200 hours to fully implement with all tests passing.
I've run a reading group for distributed systems for the last 2 years now and I do think that Raft is a better introduction to Consensus than any Paxos paper I have seen (I mean the Paxos Made Simple paper literally has bugs in it). But when I learned consensus in school, we used Paxos and Multi-Paxos and I do believe that there was a lot to be gained by learning both approaches. Heidi Howard has several amazing pape…
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Is there any paper/handouts/video that explains Paxos in depth, especially its implementations and intuitions? Paxos Made Simple gave intuitive explanations, but I feel it still misses a lot of intricate details if I were to build Praxos for production use.
The best approach is to implement Paxos. I suggest https://github.com/emichael/dslabs . It will take 100-200 hours to fully implement with all tests passing.
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I have had the opposite trajectory. Used to teach Paxos, but was so relieved to switch to Raft when the paper came out. I discuss distributed data structures in the context of maps and sequences. For maps, I discuss key-value stores (NUMA, Redis). I have them implement cache coherence (MESI protocol, TARDIS 2.0), then linearizable, fault-tolerant, wait-free shared memory registers (the Attiya/Bar-Noy/Dolev algorithm[…
I feel like you are doing your students a disservice. (multi-)Paxos, while complex to wrap your head around, enables far more modes of consensus. The possibilities and papers out there are amazing. Raft essentially only allows a single mode. Moreover, you are starting to see people putting things on top of Raft instead of something like Paxos, in the enterprise, because they don't know any better nor have the foundat…
Raft's simplicity and the fact that there's exactly one way to do it is what I find most comforting in the most important component of a distributed system. I can look at an implementation of raft and immediately understand what's going on, and what is missing.
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I feel like you are doing your students a disservice. (multi-)Paxos, while complex to wrap your head around, enables far more modes of consensus. The possibilities and papers out there are amazing. Raft essentially only allows a single mode. Moreover, you are starting to see people putting things on top of Raft instead of something like Paxos, in the enterprise, because they don't know any better nor have the foundat…
Can you tell more about what other interesting modes multiPaxos allows? For an example of what I find uninteresting, it is proposers or acceptors not having a local disk (I know there are some uses for it, but there are relatively straightforward ways of solving that issue without requiring a whole new protocol). In all examples I have seen, multipaxos and raft are fairly alike, except for parts of their leadership e…
It's like learning about a byte and never learning about endianness because everything is pretty much little-endian these days.
Off topic - folks in the know, besides Paxos/Raft what are some of the other most complex algorithm in computer sciences that are widely used or are a bedrock?
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I'm on the other side. I think Leslie Lamport asserted that Paxos is minimal, and that "all other consensus algorithms are just Paxos with more steps". I'm inclined to believe him. I've implemented Paxos but I can't get through "Raft for dummies" style blog posts. Regarding Raft [1]: > The consensus problem is divided into three sub-problems: Leader election, Replication and Safety. What is leader election? It's a di…
I tend to agree that many explanations of raft dont get into the useful details and handwave some of the hard problems. But the original paper does do a good job of this and is pretty accessible to read IMO. > I read "once the leader has been elected", um, hangon, according to whom? Has node 1 finally agreed on the leader, just while node 3 has given up and started another election? The simple response I think to "ac…
Reminds me of this one time we had a Raft cluster arguing over who was the leader for 20 minutes in production. Raft leader election is non-deterministic, while Paxos is deterministic. It can 'randomly' get into a situation it cannot resolve for quite a long time.