Cloudflare Meerkat - Globally distributed consensus

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• Hacker News
• Consensus is one of those areas where the interesting engineering and the number of people who actually need it are inversely correlated. Most "we need distributed coordination" turns out to be "we need one writer and a lock," which a single Postgres hands you for free: advisory locks, SELECT ... FOR UPDATE, SKIP LOCKED for work distribution. Linearizability without running Raft..

  The real threshold is multi-region writes on a hard latency budget, and even then a single-region primary plus accepting cross-region read latency beats eating a consensus round-trip on every write for a lot of teams. Curious what workload pushed you past single-primary - usually a better story than the impl itself.

  by s8kur
• > Most "we need distributed coordination" turns out to be "we need one writer and a lock," which a single Postgres hands you for free

  1. This article is about Cloudflare developing for their own internal control plane--I'm fairly certain their requirements preclude a single Postgres

  2. Even if you're not Cloudflare, you may not want to be limited by the availability of a single Postgres instance.

  by throwaway894345
• Can I run up some memecoins on it?
  by yieldcrv
• Illustrated with meercats looking in different directions.
  by abujazar
• 2 out of 3 meerkats look in the same direction. Enough for consensus.
  by ash
• I feel like it would be much better if the article focused on QuePaxa because IMHO it's an algorithm that finally brings some novel ideas to concensus (e.g. not relying on timeouts) by kinda coming at it from a gossip protocol angle and is not getting the attention it deserves. The post shouldn't have focused and introduced Meerkat which hasn't been fully developed and tried in production. If they clearly presented the pros and cons vs not just Raft (which is popular but doesn't even play in the same league because it is relies on a leader) but other leaderless or multi-leader concensus protocols that would have been of greater value. The Paxos family of algorithms are a much closer fit here and there's a reason why some serious large planet scale systems choose it over Raft.

  E.g. 1. Intro about issues with concensus 2. Intro to QuePaxa 3. Comparison to other algos that are close to it 4. Mentioning active work on implementation via Meerkat and intent to bring to production with followup posts.

  As always when it comes to concensus it's all about trade-offs. And with QuePaxa that might be the increase in messages (note: I don't mean message round-trips). We'll see how it goes but it will definitely be interesting.

  by eis
• TBH I’m doubtful of most people building their own crypto libs and distributed consensus implementations. But maybe cloudflare can pull it off. Good to see them pushing the state of distributed consensus.

  Take aways:

  * it’s not in prod yet. I suspect those many round trips are going to get expensive on median aka typical redistributed deployments. Curious to see how it goes once in the wild.

  * they say it isn’t likely suitable for eg databases.

  * they talk about formal verification, which is good and feels appropriate.

  Looking forward to seeing more!

  by pstoll
• Cloudflare did not develop QuePaxa, although I'm sure they did a lot of work to operationalize it. The original protocol is from a SOSP 2023 paper.

  https://dl.acm.org/doi/10.1145/3600006.3613150

  by michaelmior
• > I’m doubtful of most people building their own crypto libs and distributed consensus implementations. But maybe cloudflare can pull it off.

  Who else than Cloudflare (or similar company in expertise and size) would be a better fit to implement distributed consensus?

  by williamdclt
• This is really interesting. I wonder if etcd can benefit from this as it uses Raft for consensus and split-brain can be a problem depending on how its setup (usually when a Kubernetes control plane is initialized).
  by nunez
• Yeah, for real. etcd is one of the biggest limitations to Kubernetes in my opinion. I would love to have a region-agnostic Kubernetes cluster.
  by throwaway894345
• I imagine something akin to a bat signal that alerts Aphyr to these types of posts. Looking forward to the Jepsen write-up.
  by _cairn
• if youve ever fought a raft cluster on a bad network with leaders flapping, elections storming and latency spiking this genuinely doesnt seem that bad. i believe this will be very useful to those dealing with messy networks
  by ebeirne
• "a new distributed consensus service called Meerkat powered by a consensus algorithm called QuePaxa, published in 2023 by researchers at EPFL. QuePaxa differs from Raft in that all replicas can perform writes at all times, and progress is never halted due to a timeout"

  Interesting

  by snthpy
• This seems like something that would be great to open source; I can see it being a good building block for other globally distributed services.
  by rzz3
• What's interesting here is that this would be the first production implementation of an asynchronous consensus algorithm (QuePaxa). Paxos, Raft, etc. are all partially synchronous, meaning they rely on timeouts and only make progress if message delay is sufficiently small compared to timeout durations. QuePaxa doesn't rely on timeouts and makes progress even under wild fluctuations in message delay. The question is whether performance is competitive enough in the normal case, when message delay is small and doesn't vary much, and historically the answer has been "no" and that's why asynchronous protocols weren't used.
  by nano_o
• This article is a bit hard for me to grasp the main ideas of because, given Cloudflare's requirements (e.g. no strong leaders), it immediately seems like they should be comparing to leaderless protocols like Paxos-class algorithms. Comparing to Raft and saying it's better because Meerkat is leaderless is confusing, because Raft is an adjustment to Paxos to specifically have strong leaders. So I'm 3/4 the way into the article and I don't see what's unique here.

  I think the unique idea here is supposed to be QuePaxa's idea of avoiding timeouts for ensuring liveness. The actual discussion of QuePaxa is limited to one paragraph at the end, and tbh only a couple sentences of that paragraph.

  I feel like the article could've been titled "Consensus protocols and linearizability: a brief explainer", or "Paxos vs Raft", or similar. It just doesn't feel like it communicates what it claims to communicate, and is a bit confused on who its audience is, just IMO.

  by m11a
• Agreed on - it took a long time to get to the “so what is new here” vs the broader topic of distributed consensus. Stylistically would prefer more upfront “here is what is novel here”
  by pstoll
• It feels like somebody prompted an AI agent at CF "why Meerkat is better than Raft" when drafting this blog post.
  by buremba
• Worth noting if it wasn't obvious from the article that Cloudflare did not develop QuePaxa. It's from an SOSP paper back in 2023[0]. The article is discussing what is the first known large-scale public deployment of the protocol.

  [0] https://dl.acm.org/doi/10.1145/3600006.3613150

  by michaelmior