Metastable Failures in Distributed Systems [pdf]
I think this paper is super important, and anybody who designs or runs big systems should read it and take the core point to heart. As system designers, we're very used to thinking about systems as 'stable' and 'unstable', where stability is good, and instability is bad. What this paper points out is that many kinds of distributed systems have multiple 'stable' modes, some of which are modes where the system is stable (in a control theory sense), but not doing any useful work from the client's perspective. This is dangerous, because the system won't kick itself out of this "stable but down" mode without something changing: human input, a control plane taking action, etc.<p>I don't think this paper covers anything particularly new, but writing it down in this form, with the evidence they present, is very valuable. Hopefully this paper will deepen the conversation about applying control theory to distributed systems design and control problems, and allow a more theoretical approach to be taken to the design of these systems to avoid common causes of instability and bistability.<p>One of the authors has a great summary of the paper on his blog: <a href="http://charap.co/metastable-failures-in-distributed-systems/" rel="nofollow">http://charap.co/metastable-failures-in-distributed-systems/</a><p>I wrote a summary and discussion too: <a href="https://brooker.co.za/blog/2021/05/24/metastable.html" rel="nofollow">https://brooker.co.za/blog/2021/05/24/metastable.html</a>