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Comment by Brian_K_White | Hacker News Reader

I don't understand the load-responsive control loop one. That's a basic and fundamental component in countless systems. The centrifugal governor on a 1800's steam engine or 1900's victrola record player is a load-responsive control loop. All of electronics is a mesh of load-responsive control loops. The automatic transmission in your car...

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The usual issue is the addition of control loops without much understanding of the signals (CPU utilization is a fun one), and the addition of control loops without the consideration of other control loops. For example, you might find that your cross region load balancer gets into a fight with your in-process load shedding, because the load balancer's signals do not account for load shedding (or the way they account for the load shedding is inaccurate). Other issues might be the addition of control loops to optimize service local outcomes, to the detriment of global outcomes.

My general take is that you want relatively few control loops, in positions of high leverage.

It’s not totally clear, but it could be talking about CPU load in particular, which has some problems as described in https://arxiv.org/abs/2312.10172.

I've always used connection backlog as the metric for load and it's worked pretty well. Most web servers have it as a number you can expose as a metric. It's not perfect but it's at least a true measure of when servers are behind.

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