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Why are we templating YAML? (2019)

leebriggs.co.uk

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Re: Why are we templating YAML? (2019)

#21

Post by YawningAngel »

throwaway143829 wrote: post #2

This article made me think it'd be nice to generate k8s JSON using TypeScript. Just a node script that runs console.log(JSON.stringify(config)), and you pipe that to a yaml file in your deploy script. The syntax seems more sane and has more broad appeal than jsonnet, and I'd wager that the dev tooling would be better given good enough typings. By the way the answer to the question "why are we templating yaml?" is: pe…

You can convert YAML to JSON programmatically, and JSON is valid jsonnet, so you can pretty much copy paste examples from the web into your jsonnet if you find yourself wanting to do that

Re: Why are we templating YAML? (2019)

#23

Post by Hackbraten »

pvorb wrote: post #13
tipiirai wrote: post #8

I think YAML is a good pick for non-developers / content creators. The front matter section in Markdown files is a good example. Or is there a better, human-friendly alternative?

YAML is all but human-friendly. It has far too many special features and edge cases for most people. Something simple like Java properties files would solve something like markdown front matter perfectly fine.

Java properties files are a mess. They still require Windows encoding (ISO-8859-1), which is incompatible with UTF-8.

Re: Why are we templating YAML? (2019)

#26

Post by TheFuzzball »

I just knew this would be about Kubernetes when I saw the title.

The Kubernetes API is fairly straightforward, and has a well-defined (JSON) schema, people should be spending a bulk of their time learning k8s understanding how to use the API, but instead they spend it working out how to use a Helm chart.

I don't think Jsonnet, Ksonnet, Nu, or CUE ever gained that much traction. I'm convinced most people just use Kustomize, because it's fairly straightforward and built in to kubectl.

I'd like a tool that:

- Gives definition writers type checking against the k8s schemas - validation, version deprecations, etc.

- Gives users a single artefact that can be inspected easily and will fail (ACID) if deployed against a cluster that doesn't support any objects/versions.

- Is built into the default toolchain

---

I feel like writing a Bun or Deno TypeScript script that exports a function with arguments and returns a list of definitions would work well, esp. with `deno compile`, etc. but that violates the third point.

Re: Why are we templating YAML? (2019)

#27

Post by Joker_vD »

The title of TFA was actually my reaction when I learned what Helm was actually doing. Initially I thought Helm would take an input file of YAML-with-template-bits, parse that YAML as an object, then use the provided template bits to fill in the parts of that object, then serialize the object back to YAML and write it out. Sounds reasonable, right? Nope, it's literal text substitution, so if you want to have a valid YAML as the output you better count your indentation on your fingers, and track where the newlines go or don't go.

Re: Why are we templating YAML? (2019)

#28

Post by grncdr »

throwaway143829 wrote: post #2

This article made me think it'd be nice to generate k8s JSON using TypeScript. Just a node script that runs console.log(JSON.stringify(config)), and you pipe that to a yaml file in your deploy script. The syntax seems more sane and has more broad appeal than jsonnet, and I'd wager that the dev tooling would be better given good enough typings. By the way the answer to the question "why are we templating yaml?" is: pe…

Others have mentioned CDK, but I want to say that this is almost the exact approach I took on a project recently and it worked out fine. Node script that validates a few arguments and generates k8s manifests as JSON to be fed into `kubectl apply`.

IME, here's no need to involve anything more complicated if your deployment can be described solely as k8s manifests.

Re: Why are we templating YAML? (2019)

#30

Post by Aeolun »

datadeft wrote: post #20

Indeed why? However the conclusion I have is not to use JSON but to use a type safe configuration language that can express my intent much better making illegal states impossible. One example of such lang is Dhall. https://dhall-lang.org/

If I’m going to use a whole language to generate my config already, why would I use anything but the language my application is written in? Everything can export JSON after all.
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