I never imagined someone would write a recursive DNS sever in javascript. Have they explained why they chose javascript? It can't perform well nor scale and they even sort of admit that:
Basically, only the root record parsing is done in JS and then passed to unbound for resolution. Though it is possible to run a pure JS resolver, it's not really recommended.
Right, thanks. And I hope my question does not sound too critical. I was just genuinely curious why JS was used.
I think JS is fine for small to mid-sized tasks, prototyping and testing ideas. However, for real DNS servers, used by a lot of clients, I believe C, C++, Go or Rust would be an absolute requirement.
The JS implemention is a fork of bcoin, the JS Bitcoin full node and production backend.
It binds to libunbound but you are right that you would want a lower level language for it to be more scalable. There is a rust implemention work in progress here:
https://github.com/UrkelLabs/rsd
This is separate from the DNS resolver being written in JS, but the team behind Handshake also created bcoin, which is the only javascript fullnode (and non-core fullnode IIRC) that has mined a Bitcoin block.
There's also a more portable authoritative & recursive [resolver in C](https://github.com/handshake-org/hnsd).
Plus, the whole protocol for node communication and name resolution & proofs is so simple, that it's pretty easy to reimplement in any language.