Cloudflare Meerkat: A New Experiment in Global Consensus
Cloudflare Meerkat - Globally distributed consensus
We are introducing Meerkat, an experimental consensus service designed to manage control-plane state across our 330+ global data centers. Unlike traditional systems that rely on a single leader and struggle with network delays, Meerkat uses the QuePaxa algorithm to allow all replicas to write simultaneously. This approach ensures strong consistency and high availability even when parts of our network fail, marking the first industrial deployment of QuePaxa at this scale.
Unlike weaker forms of consistency, linearizability relieves programmers from thinking about all the weird behaviors the data systems might exhibit.
- m11a
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.
- nano_o
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.
- advisedwang
This sounds like a very direct approach to linearizability - just put everything in a linear order.
But this includes READ operations too! You have to get global consensus for every read! Most distributed systems have additional complexity and latency on write paths so that reads can be completely local. If you can accept slow read operations this seems like a great trade off, but I think that is going to relegate this to niece usage.
- eis
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.
- ebeirne
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