Closed
Description
We've outgrown command-line only configuration.
When it comes to configuration files there's a tricky balance; on one hand we don't want to stray too far from expected practices; on the other hand, common practices are fractured and leave a lot to be desired.
Some things to consider:
- It's common to have a fairly static configuration but want to set some values at runtime. How should this be accomplished?
- Caddy approach: env var templating in configuration file
- Nginx approach doesn't have built-in env var substitution, but the docker image implements it based on envsubst
- docker registry allows overriding individual yaml leaves by turning the full path to that leaf into a variable name. This is good for overriding string values, but is awkward for list/array/set values.
- It's important to be able to automatically generate configuration from popular languages, so it should be a relatively common format.
- It's important to be able to add comments to configuration, so if we were to go with something like JSON, we'd want to use a flavor that supported comments. And trailing commas.
Some options:
TOML: Rust projects tend to favor it.YAML: Popular with Go/CNCF projects, but No Body Wants To Write YAML. Superficially a superset of JSON, making it very easy to generate universally, but not without footguns.JSON: Good for generating but not for human-generated configuration.Dhall: Has some nice neat ideas but overcomplicated for our use case and still pretty obscure.CUE: Exposes less complexity than Dhall although it has a similarly thoughtful design. It could be a nice user experience with the right tooling, but I don't think the tooling is mature enough yet. Mostly targets the Go ecosystem currently.Nickel: Cool but too programming-languagey