Ask HN: What are some well written/engineered open source software?

A *BSD OS

I really like reading the go std lib and runtime source.

Asterisk PBX. Well-chosen small set of module types (channel drivers, applications, functions, resources, codecs & formats), allowing to implement literally any behaviour, and converge with any thinkable external technology. Not working in VoIP anymore for quite long time, but the clarity of design of Asterisk has deeply influenced me.

Gstreamer. Pipeline is very powerful model for software, the potential of it is tremendous. Unfortunately I find level of development & maintenance of Gstreamer project itself quite poor - the code is horribly complicated for questionable reasons (it's said to be non-blocking everywhere; I find it bad excuse for being ridden with subtle bugs and for failures to use custom pipelines as blocks for higher-level pipelines).

I find such projects as ffmpeg and linux kernel quite well engineered, but have nothing special to say about them except that they are reasonably well organized and get better day by day.

For user-interface apps with considerations of high user productivity, I find such software as readline, tmux, mutt and bunch of other following wise pattern of extensible and scriptable software: if you want hotkeys, you need a domain-specific language and bindings must be

  key: action[, action...]

not

  action: key

Chromium

edit: https://www.chromium.org/developers/design-documents

I'm only familiar with varnish 2.1, but as to that version I think it's a bit of a stretch to say varnish is well written. VCL is very complicated - just check the request flow diagram [1]. Some of the documentation is very poor - try to find out the properties available on beresp for example (you have to grep the source code [2]), or try to understand the precise function and implications of grace mode, saint mode, or hit_for_pass. The best redeeming quality is varnishtest and some of the other tools that are provided.

[1] http://book.varnish-software.com/3.0/_images/request.png

[2] https://github.com/varnishcache/varnish-cache/blob/2.1/lib/l...