kubectl apply --kustomize manifests/ --prune --selector app=myapp
It cleans up old stuff from the cluster and also allows you to split your manifests across multiple files.
I did not think about a “delete”, and I usually don’t want it to be automatically deleted. But that’s a great idea for that convergence mechanism if I have something that explicitly adds a deleted resource line to make sure it stays deleted until otherwise specified.
The Ruby code can access anything Ruby to generate the manifests, so I have a Turing-complete language and I can use class inheritance, mixins, method overrides. I was also able to write a suite of helpers to take a raw yaml manifest from an upstream project, and use a functional programming style to transform the manifest to something else. If I ever have time, I’d write the ability to import templates from Helm.
This was written for a one-person devops role, intended to be able to manage almost-similar things across different environments (dev, staging, prod), which works great for small, early stage startups, for our level of complexity. At this level, I don’t need it to track state.
When our team size grows, I’ll have to think up of some other patterns to make it easier for multiple people to work on this.
The other thing is that for much more complex things, I would just write operator code using Elixir, and bootstrap that into k8s with the Ruby framework.
I've built these kinds of things too in Python (or Starlark). It's an improvement over YAML, but I often feel the pain of dynamic typing.
> The Ruby code can access anything Ruby to generate the manifests, so I have a Turing-complete language and I can use class inheritance, mixins, method overrides.
I actually don't want any of these things in a dynamic configuration language. I kind of just want something that can evaluate expressions (including functions, objects, arrays, scalars, and pattern matching). If it's Turing complete that's fine but unnecessary. I explicitly don't want I/O (not in your list) or inheritance, mixins, method overrides, etc--unnecessary complexity.
Dhall probably comes the closest, but it has a tragic syntax and I'm not a good enough salesman to persuade real software teams to learn it. I've also heard good things about Cue, but my experiences playing with it have only been painful (steep learning curve, don't really see the upsides).
I use classes and mixins to be able to generate similar manifests with slight differences across different clusters or environments. I sometimes use imports (I/O) for manifests provided by an upstream (such as from AWS docs), do transforms to get manifest I want.
I modelled the design off of Chef, which will also declaritively define and converge a set of systems towards desired state. Well-known paths and conventions helps keep things organized.
I havn't had a problem with dynamic typing, but I have also been using Ruby in application development for over 10 years. You might see it as unneeded complexity, but I have been able to use the flexibility for years now. This tooling was designed for a team that uses Ruby as the primary language, and uses designs and idom that would be familiar for a Ruby dev team. It is definitely opinionated and I don't expect it to be universally useful for everyone.
This is fine for the first deploy, but if you delete a resource from your manifests then kubectl doesn’t try to delete it from the cluster, so in practice you need something like Terraform (or perhaps ArgoCD) which actually tracks state. And of course as you mention, you probably want to generate these manifests to DRY up your YAML so you can actually maintain the thing.
I would love to hear from others how they solve these problems.
> as the whole idea of text templating YAML is... thoroughly ignorant
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