What are usual cold-start times you see with firecracker?
What other VMMs or Unikernels did you consider before settling on firecracker?
Was the firecracker documentation good enough or did you have to go digging through emails or code to figure out certain things?
What was the hardest part of using firecracker in production?
Thanks.
Cold starts depend a lot on what people actually deploy. They're really fast for an optimized Go binary, really slow for most Node apps. We were playing with Deno + OSv just today and got an app to boot and accept an HTTP request in about 20ms. That assumes you have the root fs all built and ready to go, though, pulling down images and prepping everything is a bit of a bottleneck for that.
We looked at gvisor pretty hard but preferred more traditional virtualization. We didn't look much at other virtualization options, Firecracker was really good from day one.
The docs were pretty good. We ended up having to build a bunch, though, probably just because of the nature of our product. We built a custom init (in Rust), a Docker image to root fs builder, and a nomad task driver (both in Go). The init includes and rpc mechanism so we can communicate with the VM.
Firecracker was pretty easy, building the scaffolding to use it was a little harder, but the vast majority of our time is spent on the dev UX and proxy/routing layer.
Core product in Rust, Firecracker Micro-VMs, Nomad instead of k8s (never used it myself but see the strong value in it and think it makes sense + deserves more attention), and experimentation with Deno (huge fan).
I wish I could clone myself and do some work for you guys just to soak up that knowledge.